The successful application of paint, whether for artistic or preservative purposes, necessitates careful attention to a number of considerations, some of a mechanical and others of a chemical character.

The Surface.—Of whatever the surface may be to which the paint is to be applied, great care must be taken that it is perfectly dry. Wood especially, even when apparently dry, may on a damp day contain as much as 20 per cent. of moisture. A film of paint applied to the surface of wood in this condition prevents the moisture from escaping, and it remains enclosed until a warm sun or artificial heat converts it into vapour, which raises the paint and causes blisters. Moisture enclosed between two coats of paint has the same effect. Paint rarely blisters when applied to wood from which old paint has been burnt off; this is probably due to the drying of the wood during the operation of burning.

When the surface to be painted is already covered with old paint, this should be either removed or rubbed down smooth before applying the new. When the thickness of the old coat is not great, rubbing down, accompanied by a careful scraping of blisters and defective parts, will suffice. When the thickness of the old paint necessitates its removal, it may either be burned off, or softened by a solution of caustic alkali, and afterwards scraped. The burning process is the most effective, and leaves the wood in a fit condition to receive the fresh coat of paint; but it is not applicable in the case of fine mouldings. When caustic potash or soda is used, the paint is left in contact with, it for some time, when the linoleic acid of the oxidised linseed-oil becomes saponified, and can easily be scraped or scrubbed off the surface of the wood.

Whenever an alkali is employed, it is of the greatest importance that the wood should afterwards be thoroughly washed several times with clean water, in order to remove every trace of the solvents. Any soda or potash remaining in the pores of the wood would not only retain moisture and cause blistering, but would also have an injurious action upon the vehicle of the paint subsequently applied, and in many cases upon the pigment itself. The remarks already made as to the necessity of an absolutely dry surface should be borne in mind in this instance. When the surface of the paint is to be protected by a coat of varnish, the latter should not be applied until the whole of the oil contained in the paint has solidified. The wrinkling of varnish upon paint is frequently erroneously attributed to the bad quality of the varnish, when the real cause is the incomplete oxidation of the paint itself.

Priming.—The first coat of paint applied to any surface is termed the “priming-coat.” It usually consists of red lead and boiled and raw linseed-oil. Experience has shown that such a priming not only dries quickly itself, but also accelerates the drying of the next coat. The latter action must be attributed to the oxygen contained in the red lead, only a small portion of which is absorbed by the oil with which it is mixed.

Kali, of Heidelberg, prepares a substitute for boiled oil by mixing 10 parts whipped blood, just as it is furnished from the slaughter-houses, with 1 part of air-slaked lime sifted into it through a fine sieve. The two are well mixed and left standing for 24 hours. The dirty portion that collects on top is taken off, and the solid portion is broken loose from the lime at the bottom; the latter is stirred up with water, left to settle, and the water is poured off after the lime has settled. The clear liquid is well mixed up with the solid substance before mentioned. This mass is left standing for 10 or 12 days, after which a solution of potash permanganate is added, which decolorises it and prevents putrefaction. Finally the mixture is stirred up, diluted with more water to give it the consistence of very thin size, filtered, a few drops of oil of lavender are added, and the preparation is preserved in closed vessels. It is said to keep a long time without change. A single coat of this liquid will suffice to prepare wood or paper, as well as lime or hard plaster walls, for painting with oil colours. This substance is cheaper than linseed oil, and closes the pores of the surface so perfectly that it takes much less paint to cover it than when primed with oil.

Drying.—The drying of paint is to a great extent dependent upon the temperature. Below the freezing point of water, paint will remain wet for weeks, even when mixed with a considerable proportion of dryers; while, if exposed to a heat of 120° F. the same paint will become solid in a few hours. The drying of paint being a process of oxidation, and not evaporation, it is essential that a good supply of fresh air should be provided. When a film of fresh paint is placed with air in a closed vessel, it does not absorb the whole of the oxygen present; but after a time the drying process is arrested, and the remaining oxygen appears to have become inert.

Considerable quantities of volatile vapours are given off during the drying of paint; these are due to the decomposition of the oil. When the paint has been thinned down by turpentine, the whole of this liquid evaporates on exposure to the air. There must, therefore, be a plentiful access of air, to remove the vapours formed, and afford a fresh supply of active oxygen. The presence of moisture in the air is rather beneficial than injurious at this stage. Especially in the case of paints mixed with varnish, moist air appears to counteract the tendency to crack or shrink. Under the erroneous impression that the drying of paint is a species of evaporation, open fires are sometimes kept up in freshly-painted rooms. It is only when the temperature is very low that any benefit can result from this practice; as a rule, it rather retards than hastens the solidification of the oil, which cannot take place rapidly in an atmosphere laden with carbonic acid.

The first coat of paint should be thoroughly dry before the second is applied. Acrylic acid is formed during the oxidation of linseed-oil, and unless this be allowed to evaporate, it may subsequently liberate carbonic acid from the white lead present in most paints, and give rise to blisters. Sometimes a second priming-coat is given; but usually the second coat applied contains the pigment. This, as soon as dry, is again covered by another coat, and subsequently by two or more finishing coats, according to the nature of the work.

Filling.—Before the first coat is applied to wood, all holes should be filled up. The filling usually employed is ordinary putty; this, however, sometimes consists of whiting ground up with oil foots of a non-drying character, and when the films of paint are dry, the oil from the putty exudes to the surface, causing a stain. The best filling for ordinary purposes is whiting ground to a paste with boiled linseed-oil. For finer work, and for filling cracks, red lead mixed with the same vehicle may be employed. For porous hard woods, use boiled oil and corn starch stirred into a very thick paste; add a little japan, and reduce with turpentine. Add no colour for light ash; for dark ash and chestnut, use a little raw sienna; for walnut, burnt umber and a slight amount of Venetian red; for bay wood, burnt sienna. In no case use more colour than is required to overcome the white appearance of the starch, unless you wish to stain the wood. This filler is worked with brush and rags in the usual manner. Let it dry 48 hours, or until it is in condition to rub down with No. 0 sand-paper without much gumming up; and if an extra fine finish is desired, fill again with the same materials, using less oil, but more japan and turpentine. The second coat will not shrink, being supported by the first. When the second coat is hard, the wood is ready for finishing up by following the usual methods. This formula is not intended for rosewood.

Coats.—There is no advantage in laying on the paint too thickly. A thick film takes longer to dry thoroughly than two thin films of the same aggregate thickness. Paint is thinned down or diluted with linseed-oil or turpentine. The latter liquid, when used in excess, causes the paint to dry with a dull surface, and has an injurious effect upon its stability. Sometimes the last coat of paint is mixed with varnish, in order to give it greater brilliancy. In this case, special care must be taken that the previous coats have thoroughly solidified, or cracks in the final coat may subsequently appear. The same remark applies when the surface of the paint is varnished. The turpentine with which the varnish is mixed has a powerful action upon the oil contained in the paint, if the latter is not thoroughly oxidised. The exterior of the paint is thus softened, and the varnish is enabled to shrink and crack, especially in warm weather.

Brushes.—The bristles are frequently fastened by glue or size, which is not perceptibly acted upon by oil, and if brought into contact with this liquid alone, there would be no complaints of loose hairs coming out and spoiling the work. It is a common practice to leave the brushes in a paint-pot, in which the paint is covered with water to keep it from drying. The brushes are certainly kept soft and pliant in this way; but at the same time the glue is softened, and the bristles come out as soon as the brush is used. After use, brushes should be cleaned, and placed in linseed-oil until again required, when they will be found in good condition. Treated in this way, they will wear so much better that the little additional trouble entailed is amply repaid. When brushes will not again be required for some time, the oil remaining in them should be washed out by means of turpentine, after which they may be dried without deterioration. On no account should oil be allowed to dry in a brush, as it is most difficult to remove after oxidation has taken place. The best means are steeping in benzoline for a few days, or in turpentine, with occasional washing in soda-water and with soft-soap, avoiding too violent rubbing.

Water-colours.—The manufacture of water-colour paints is more simple than that of oil paints, the pigments being first ground extremely fine and then mixed with a solution of gum or glue. The paste produced in this manner is allowed to dry, after having been stamped into the form of cakes. As soon as the hardened mass is rubbed down with water, the gum softens and dissolves, and if the proportion of water be not too great, the pigment will remain suspended in the solution of gum, and can be applied in the same manner as oil-paint. To facilitate the mixing with water, glycerine is sometimes added to the cake of paint, which then remains moist and soft.

Removing Odour.—(1) Place a vessel of lighted charcoal in the room, and throw on it 2 or 3 handfuls of juniper berries; shut the windows, the chimney, and the door close; 24 hours afterwards the room may be opened, when it will be found that the sickly, unwholesome smell will be entirely gone. (2) Plunge a handful of hay into a pail of water, and let it stand in the room newly painted.

Discoloration.—Light-coloured paints, especially those having white lead as a basis, rapidly discolour under different circumstances. Thus white paint discolours when excluded from the light; stone colours lose their tone when exposed to sulphuretted hydrogen, even when that is only present in very small quantity in the air; greens fade or darken, and vermilion loses its brilliancy rapidly in a smoky atmosphere like that of London.

Ludersdorf thinks that the destructive change is principally due to a property in linseed-oil which cannot be destroyed. The utility of drying oils for mixing pigments depends entirely on the fact that they are converted by the absorption of oxygen into a kind of resin, which retains the colouring pigment in its semblance; but during this oxidation of the oil—the drying of the paint—a process is set up which, especially in the absence of light and air, soon gives the whitest paint a yellow tinge. Ludersdorf therefore proposes to employ an already formed but colourless resin as the binding material of the paint, and he selects two resins as being specially suitable—one, sandarach, soluble in alcohol; the other, dammar, soluble in turpentine. The sandarach must be carefully picked over, and 7 oz. is added to 2 oz. Venice turpentine and 24 oz. alcohol of sp. gr. 0·833. The mixture is put in a suitable vessel over a slow fire or spirit-lamp, and heated, stirring diligently, until it is almost boiling. If the mixture be kept at this temperature, with frequent stirring for an hour, the resin will be dissolved, and the varnish is ready for use as soon as cool. The Venice turpentine is necessary to prevent too rapid drying, and more dilute alcohol cannot be employed, because sandarach does not dissolve easily in weaker alcohol, and, furthermore, the alcohol, by evaporation, would soon become so weak that the resin would be precipitated as a powder.

When this is to be mixed with white lead, the latter must first be finely ground in water, and dried again. It is then rubbed with a little turpentine on a slab, no more turpentine being taken than is absolutely necessary to enable it to be worked with the muller; 1 lb. of the white lead is then mixed with exactly ½ lb. of varnish, and stirred up for use. It must be applied rapidly, because it dries so quickly. If when dry the colour is wanting in lustre, it indicates the use of too much varnish. In such cases, the article painted should be rubbed, when perfectly dry, with a woollen cloth to give it a gloss. The dammar varnish is made by heating 8 oz. dammar in 16 oz. turpentine oil at 165° to 190° F., stirring diligently, and keeping it at this temperature until all is dissolved, which requires about an hour. The varnish is then decanted from any impurities, and preserved for use. The second coat of the pure varnish, to which half its weight of oil of turpentine has been added, may be applied. It is still better to apply a coat of sandarach varnish made with alcohol, because dammar varnish alone does not possess the hardness of sandarach, and when the article covered with it is handled much, does not last so long.

Composition.—The composition of paints should be governed—

(1) By the nature of the material to be painted: thus the paints respectively best adapted for wood and iron differ considerably.

(2) By the kind of surface to be covered: a porous surface requires more oil than one that is impervious.

(3) By the nature and appearance of the work to be done: delicate tints require colourless oil, a flatted surface must be painted without oil (which gives gloss to a shining surface), paint for surfaces intended to be varnished must contain a minimum of oil.

(4) By the climate and the degree of exposure to which the work will be subjected: for outside work, boiled oil is used, because it weathers better than raw oil; turps is avoided as much as possible, because it evaporates and does not last; if, however, the work is to be exposed to the sun, turps is necessary, to prevent the paint from blistering.

(5) The skill of the painter affects the composition: a good workman can lay on even coats with a smaller quantity of oil and turps than one who is unskilful; extra turps, especially, are often added to save labour.

(6) The quality of the materials makes an important difference in the proportions used: thus more oil and turps will combine with pure than with impure white lead; thick oil must be used in greater quantity than thin when paint is purchased ready ground in oil, a soft paste will require less turps and oil for thinning than a thick.

(7) The different coats of paint vary in their composition: the first coat laid on to new work requires a good deal of oil to soak into the material; on old work, the first coat requires turpentine to make it adhere; the intermediate coats contain a proportion of turpentine to make them work smoothly; and to the final coats the colouring materials are added, the remainder of the ingredients being varied according as the surface is to be glossy or flat.

The exact proportions of ingredients best to be used in mixing paints vary according to their quality, the nature of the work required, the climate, and other considerations. The composition of paint for different coats also varies considerably. The proportions given in the following table must only be taken as an approximate guide when the materials are of good quality:—

Table showing the Composition of the different Coats of White Paint, and the Quantities required to cover 100 yd. of newly-worked Pine.

Area Covered.—For every 100 sq. yd., besides the material enumerated in the foregoing, 2½ lb. white lead and 5 lb. putty will be required for stopping. The area which a given quantity of paint will cover depends upon the nature of the surface to which it is applied, the proportion of the ingredients, and the state of the weather. When the work is required to dry quickly, more turpentine is added to all the coats. In repainting old work, two coats are generally required, the old paint being considered as priming. Sometimes another coat may be deemed necessary. For outside old work exposed to the sun, both coats should contain 1 pint turpentine and 4 pints boiled oil, the remaining ingredients being as stated in the foregoing table. The extra turpentine is used to prevent blistering. In cold weather, more turpentine should be used to make the paint flow freely.

According to another authority, it is found that in painting wood, one coat takes 20 lb. lead and 4 gal. oil per 100 sq. yd.; the second coat, 40 lb. lead and 4 gal. oil; and the third the same as the second; say 100 lb. lead and 16 gal. oil per sq. yd. for the three coats. The number of square yards covered by one gallon of priming colour is found to be 50; of white zinc, 50; of white lead paint, 44; of lead colour, 50; of black paint, 50; of stone colour, 44; of yellow paint, 44; of blue colour, 45; of green paint, 45.

Measuring.—Surface painting is measured by the superficial yard, girting every part of the work covered, always making allowance for the deep cuttings in mouldings, carved work, railings, or other work that is difficult to get at. Where work is very high, and scaffolding or ladders have to be employed, allowances must be made. The following rules are generally adopted in America in the measurement of work:—Surfaces under 6 in. in width or girt are called 6 in.; from 6 to 12 in., 12 in.; over 12 in., measured superficial. Openings are deducted, but all jambs, reveals, or casings are measured girt. Sashes are measured solid if more than two lights. Doors, shutters and panelling are measured by the girt, running the tape in all quirks, angles or corners. Sash doors measure solid. Glazing, in both windows and doors, is always extra. The tape should be run close in over the battens, on batten doors, and if the stuff is beaded, add 1 in. in width for each bead. Venetian blinds are measured double. Dentels, brackets, medallions, ornamented iron work, balusters, lattice work, palings, or turned work, should all be measured double. Changing colours on base boards, panels, cornices, or other work, one-fourth extra measurement should be allowed for each tint. Add 5 per cent. to regular price for knotting, puttying, cleaning, and sand-papering. For work done above the ground floor, charge as follows:—Add 5 per cent. for each story of 12 ft. or less, if interior work; if exterior work, add 1 per cent. for each foot of height above the first 12 ft.

Carriage and Car Painting.—The following is the substance of an address delivered by McKeon, secretary and treasurer of the Master Car-Painters’ Association of the United States:—A first-class railway coach costs, when complete, about 1200l. To protect this work, the painter expends 60l. to 120l. The latter figure will make a first class job. The car has been completed in the wood-shop, and is turned over to the painter, who is responsible for the finish. He is expected to smooth over all rough places or defects in the wood, which requires both patience and skill to make the work look well. Twelve weeks should be the time allowed to paint a car, and it cannot be done in any less time, to make a good job that will be a credit to the painter and all other parties interested in the construction and finish of the car. Too much painting is done in a hurry: proper time is not given the work to dry or become thoroughly hardened before it is run out of the shop, and consequently it does not always give the satisfaction it should; nor can it be expected that hurried work will be so lasting or durable as that which has the necessary time given to finish it.

Priming Paint.—The priming coat of paint on a car is of as much importance as any succeeding one, and perhaps more. Good work is ruined in the priming by little or no attention being given by the painter to the mixing and application of the first coat. The foundation is the support, and on that rests success or failure. The priming should be made of the proper material, mixed with care from good lead and good oil, and not picked up from old paints which have been standing mixed, and must necessarily be fat and gummy, for such are unfit for use on a good job, and will have a decided tendency to spoil the whole work. Special care should be exercised, both in mixing and applying the priming, and it should be put on very light, so that it may penetrate well into the wood. Too much oil is worse than not enough. Good ground lead is by far the best material for the undercoats on a car. Two coats should be given to the car before it is puttied, as it is best to fill well with paint the nail-holes and plugs, as well as defects in the wood, so that moisture may not secure a lodgment, which otherwise will cause the putty to swell, although sometimes unseasoned lumber will swell the putty; and as it shrinks, the nail remains stationary, and of course the putty must give way.

Best Putty.—In mixing putty, which may be a small matter with some, take care to so prepare it that it will dry perfectly hard in 18 hours. Use ground lead and japan, stiffening up with dry lead, and whatever colouring you may require in it to match your priming coats.

The next coats, after the work is well puttied, should be made to dry flat and hard. Two coats should be applied, and, for all ordinary jobs or cheap work, sand-papering is all that is necessary for each coat; but when a good surface is required, I would recommend one coat to be put on heavy enough to fill the grain; and before being set, scrape with a steel scraper. The plain surface is all that requires coating and scraping with the heavy mixture. For this coat, which is called filling, use one-half ground lead and any good mineral which experience has shown can be relied on. This scraping of the panel work will fill the wood equal to two coats of rough stuff, and saves a great amount of labour over the old process, when so much rubbing with lump pumice was done. Sand-paper when the filling is thoroughly hard, and apply another coat of paint of ordinary thickness, when, after another sand-papering, you have a good surface for your colour.

Rough-coating on cars has gone almost out of use, and few shops are now using it to any extent. My experience is that paint has less tendency to crack where rough stuff is left off. I do not claim that the filling was the principal cause of the cracking, if it was properly mixed; but I believe the water used in rubbing down a car with the lump pumice injures the paint, as it will penetrate in some places, particularly around the moulding plugs.

Finishing Colour.—The car being ready for the finishing colour, this should be mixed with the same proportion of dryer as the previous coat, or just sufficient to have it dry in about the same time. A great error with many car painters is using a large portion of oil in the under coats, and then but little, if any, in the finishing coats; this has a decided tendency to crack, the under coats being more elastic. Always aim to have colour dry in about the same time, after you have done your priming; by this plan you secure what all painters should labour to accomplish—namely, little liability to crack. Work will of course crack sometimes after being out a few months, or when it has repeated coatings of varnish; and using a quick rubbing varnish on work will cause it to give way in fine checks quicker than anything else. Many of the varnishes used are the cause of the paint cracking, and no painter has been wholly exempt from this trouble.

Cause of Cracking.—The most common cause of cracking is poor japan, which is the worst enemy that the car-painter has to contend with. The greater part of the japan is too elastic, and will dry with a tack, and the japan gold size has generally the same fault, although the English gold size is generally of good quality; but its high price is an objection to its use. A little more care in the manufacture of japans would give a better dryer, and few would object to the additional cost. Japan frequently curdles in the paint; it will not mix with it, but gathers in small gummy particles on the top. Work painted with such material cannot do otherwise than crack and scale, and the remedy lies only in getting a good pure article of turpentine japan.

In regard to using ground lead, car-painters differ, as some prefer to grind their own in the shop. I use the manufactured lead, and my reasons for doing so are that it is generally finer than any shop can grind it with present facilities, and it has age after grinding, which improves its quality. You can also get a purer lead and one with more body than you can by grinding in the shop, which is a fact that I think most painters must admit. I have tested it very fully, and am convinced on this point.

Mixing the Paints.—Permit me to make a few suggestions here in regard to the mixing of paint, which may not fully agree with others’ views. There is just as much paint that cracks by putting it on too flat as by using too much oil. Some painters mix their finishing colour so that it is impossible to get over a panel of ordinary size before it is set under the brush, and consequently the colour will rough up. Colour should be mixed up so that it will not flat down for some time after leaving it, and then you have got some substance that will not absorb the varnish as fast as it is applied to the surface. This quick drying of colour is not always caused by want of oil in it, but because there is too much japan, and a less quantity of the latter will do better work, and make a smoother finish. Give your colour 48 hours to dry between coats; always give that time, unless it is a hurried job, and experience has fully demonstrated that it is poor economy to hurry work out of the shop before it is properly finished.

Oils, Dryers, and Colours.—In car-painting, both raw and boiled oils are used, and good work may be done with either, but I recommend oil that is but slightly boiled, in preference to either the raw or the boiled. After it is boiled, if it is done in the shop, let it stand 24 hours to settle, then strain off carefully; this takes out all the impurities and fatty matter from the oil, and it will dry much better, nor will it have that tack after drying that you find with common boiled oil. Use the proper quantity of dryer in mixing your paint, and a good reliable job will be the result. In car-painting, never use prepared colours which are ground in oil, as nine-tenths of such colours are ground in very inferior oil, and they may have been put up for a great length of time, in which case they become fatty, and will invariably crack. These canned colours do not improve with age, as lead and varnish do.

Finishing colours should all be ground in the shop, unless special arrangements can be made with manufacturers to prepare them; and the colour should be fresh, not over 6 or 8 days old after being mixed, and open to the air. Enough may be prepared at a time to complete the coating on a job; but when colour stands over a week it is not fit to use on first-class work, as it becomes lifeless, and has lost that free working which we find in freshly-mixed colours. Such colour may, however, be used upon a cheap class of work, or on trucks, steps, &c., so that nothing need be wasted in the shop.

Varnishing.—Three coats of varnish over the colour are necessary on a first-class coach. The first coat should be a hard drying varnish put on the flat colour; the quick rubbing that some use I would not recommend, but one that will dry in five days (in good drying weather) sufficiently hard to rub, is the best for durability. After striping and ornamenting the car, and when thoroughly washed, give a coat of medium dry varnish. Let this stand 8 days; then rub lightly with curled hair or fine pumice, and apply the finishing coat, which is “wearing body;” this will dry hard in about 10 days, after which the car may be run out of the shop. It should then be washed with cold water and a soft brush, and is ready for the road. In varnishing, many will apply the varnish as heavy as they can possibly make it lie, when, as a consequence, it flows over and runs or sags down in ridges, and of course does not harden properly; this also leaves a substance for the weather to act on. It is better to get just enough on at a coat to make a good even coating which will flow out smooth, and this will dry hard, and will certainly wear better than the coat that is piled on heavily.

Varnishing, we claim, can be over-done, despite some painters’ opinions to the contrary. We have heard of those who put 2½ gal. on the body of a 50-foot car at one application, and we have also listened to the declaration, made by a member of the craft, that he put 2 gal. on the body of a locomotive tank. Such things are perhaps possible, and may have been done; but if so, we know that the work never stood as well as it would if done with one-half the quantity to a coat. In varnishing a car, care should be taken to have the surface clean; water never injures paint where it is used for washing; and a proper attention to cleanliness in this respect, and in the care of brushes used for varnishing, will ensure a good-looking job.

Perhaps your shop facilities for doing work are none of the best, but do the best you can with what you have. Select if possible, a still, dry day for varnishing, especially for the finishing coat. Keep your shop at an even temperature; avoid cold draughts on the car from doors and windows; wet the floor only just sufficient to lay the dust, for if too wet, the dampness arising will have a tendency to destroy the lustre of your varnish. Of course we cannot always do varnishing to our perfect satisfaction, especially where there are 25 or 30 men at work in an open shop, and 6 or 8 cars are being painted, when more or less dirt and dust are sure to get on the work.

A suggestion might here be made to railroad managers, which is that no paint-shop is complete where the entire process of painting and finishing a car is to be done in one open shop. A paint-shop should be made to shut off in sections by sliding doors, one part of the shop being used exclusively for striping and varnishing. I know from experience that nine-tenths of the railroad paint-shops are deficient in this particular, and still we are expected to turn out a clean job, no matter what difficulties we are compelled to labour under.

Importance of Washing Cars.—In regard to the care of a car after it has left the shop, more attention should be given to this than is done on many roads. The car should not be allowed to run until it is past remedy, and the dirt and smoke become imbedded in the varnish, actually forming a part of the coating, so that when you undertake to clean the car you must use soda or soap strong enough to cut the varnish before you succeed in removing the dirt. Cars should be washed well with a brush and water at the end of every trip. This only will obviate the difficulty, and these repeated washings will harden the varnish as well as increase its lustre. We know that, in washing a car, where soap is required to remove the dirt and smoke, it is almost impossible to get the smoke washed off clean; and if it is not quite impossible, the hot sun and rain will act on the varnish and very soon destroy it.

Re-varnishing.—Cars should be taken in and re-varnished at least once in 12 months; and if done once in 8 months it is better for them, and they will require only one coat; but where they run a year, they will generally need two coats. Those varnished during the hot months will not stand as well as if done at any other time. Painting done in extremely cold weather, or in a cold shop, is more liable to crack than if done in warm weather.

How to Dry Paint.—Paint dried in the shop where there is a draught of dry air passing through, will stand better than that dried by artificial heat; and you will find, by giving it your attention, that work which has failed to stand, and which cracked or scaled, was invariably painted in the winter season, or in cool, wet weather. I have paid some attention to this matter, and know the result.

Woodwork Painting.—One of the attendant drawbacks of houses that are newly built, or have been hastily finished for letting, is the inferior painting of the woodwork, and its speedy destruction. The wood is not thoroughly dry, and the consequence is the preparatory coat does not adhere; the pores being full of dampness, it is impossible for the oil to sink into them, especially as oil and water are unmiscible. Another equally injurious condition is the gum-resin which exudes from the knots of new pine and other timber. Painted over before it has time to come to the surface, the coat is destroyed by the action of the gum. Now, these evils have to be endured so long as the wood has no time to get seasoned. The painter follows the carpenter without any interval of time, and before the action of the weather can bring out the moisture and resinous substances. A coating of shellac is usually given to the knots, though this is often so thin as to be worthless. Crude petroleum, as a preservative coat, is found to be an admirable preparation for the painting. The petroleum is thin, and penetrates the wood, filling up the pores, and giving a good ground for the coats of paint.

According to one American authority, the preparation is of great value. The priming coat should be thin and well rubbed in, and it is better to use a darker colour than white lead as a base. White lead forms a dense covering to the surface, though it has its disadvantages. When petroleum has formed the first coat, two other coats will suffice, one being the priming coat, and a third coat may be given after the work has stood for a season. It is a very desirable plan to leave the painting, or rather finishing coats, for a time, so that any imperfections in the wood or work may be discovered; it also allows time for any change of colour that may be made. After the priming coat, it is usual in good work to stop all cracks, nail-holes, and other defects with putty; but in the commoner class of paintings, the coats are laid on quickly, the preceding coat has hardly time to dry before the next is put on, and all the defects of wood, bad seasoning, exudation of gum, &c., quickly begin to show themselves through and disfigure the work.

A good paint ought to possess body, power of covering, and flow evenly from the brush, and become hard. Though zinc white has less body than white lead, it is more durable, and will stand sulphur acids without blackening. Some colours stand better than others; the ochres, Indian and Venetian reds, burnt and raw umber, are reliable, and may be used without scruple. It is also worthy of notice that salt air acts injuriously on white lead, and zinc white is therefore preferable in situations exposed to the sea-air. (English Mechanic.)

Iron Painting.—The decay of iron becomes very marked in certain situations, and weakens the metal in direct proportion to the depth to which it has penetrated; and although where the metal is in quantity this is not very appreciable, it really becomes so when the metal is under ¾ inch in thickness. The natural surface of cast iron is very much harder than the interior, occasioned no doubt by its becoming chilled, or by its containing a large quantity of silica, and this affords an excellent protection.

But should this surface be at all broken, rust immediately attacks the metal and soon destroys it. It is very desirable that the casting be protected, and a priming coat of oil or paint should be applied for this purpose; the other coats, though requisite, can be given at leisure.

The following is a process to which all cast-iron water pipes should be submitted. It was introduced by Dr. Smith, and is equally applicable to any other casting that can be manipulated:—Each casting is thoroughly dressed, and made clean and free from the earth and sand which cling to the iron in the moulds, hard brushes being used in finishing the process to remove the loose dust. Every casting must be likewise free from rust when the paint is applied. If the casting cannot promptly be dipped after being cleansed, the surface must be oiled with linseed oil to preserve it until it is ready to be dipped. No casting is on any account to be dipped after rust has set in. The coal-tar pitch used as a paint in this process is made from coal-tar distilled until the naphtha is entirely removed and the material is deodorised. In England it is distilled until the pitch is about the consistence of wax. The mixture of 5 or 6 per cent. of linseed oil is recommended by Dr. Smith. Pitch which becomes hard and brittle when cold will not answer for this use. Pitch of the proper quality having been obtained, it must be carefully heated in a suitable vessel to a temperature of 300° F., and must be maintained at not less than this temperature during the time of dipping. The material will thicken, and deteriorate after a number of pieces have been dipped; fresh pitch must, therefore, frequently be added, and occasionally the vessel must be entirely emptied of its old contents and refilled with fresh pitch. The refuse will be hard and brittle like common pitch, and consequently worthless for the purpose. Every casting must attain a temperature of 300° F., either by previous heating or during the immersion before being removed from the vessel of hot pitch. It may then be slowly removed, and laid upon skids to drip. In the case of water pipes, all those of 20 inches diameter and upwards will have to remain at least 30 minutes in the hot fluid to attain this temperature. The coating when cold should be tough and tenacious, and not brittle nor have the slightest tendency to scale off.

In considering the painting of wrought iron it must be noticed that when iron is oxidised by heating in contact with the atmosphere, two or three distinct layers of scale form on the surface, and, unlike the skin upon cast iron, can be readily detached, as by bending or by hammering the metal. The outer layer of this scale is more highly oxidised than the inner, and is slightly redder in tinge from the presence of a variable excess of ferric oxide over that contained in the inner layer. The oxide occurring in the outer scale is fusible only at a high temperature, is strongly magnetic, and slightly metallic in lustre; while the inner layers are more porous, dull, and non-metallic in lustre, less brittle, and also less powerfully magnetic. It will be seen that the iron has a tendency to rust from the moment it leaves the hammer or rolls, and that the scale above described must come away. One of the plans to preserve the iron has been to coat it with paint when still hot at the mill; and although this answers for a while, it is a very troublesome method, which iron-masters cannot be persuaded to adopt, and the subsequent cutting processes to which it is submitted leave many parts of the iron bare. Besides, a good deal of the scale remains, and until this has fallen off, or has been removed, any painting over it will be of little value. The only effectual way of preparing wrought iron is to effect a thorough and chemical cleansing of the surface of the metal upon which the paint is to be applied, that is, it must be immersed for three or four hours in water containing from 1 to 2 per cent. of sulphuric acid. The metal is afterwards rinsed in cold water, and, if necessary, scoured with sand, put again into the acid bath or pickle, and then well rinsed.

The real value of any paint depends upon the quality of the linseed oil, the quality and character of the pigment, and the care bestowed on the grinding and mixing, and as all this is entirely a matter of expense, cheap paints are not to be relied upon. The superiority of most esteemed paints is due to the above causes rather than to any unknown process or material employed in the manufacture.

The following excellent article on the preservation of iron and steel structural work appeared in the ‘Illustrated Carpenter and Builder.’ It conveys the most recent American opinion.

One of the most important economic questions of the present day is the preservation of iron and steel structures. In America many millions of dollars are annually spent in the erection and construction of these, and the amount is increasing in rapid proportion. Bridges, buildings, viaducts, ships, and machinery are now being made of these materials, to almost the entire exclusion of others. From their very nature iron and steel are peculiarly subject to decay from atmospheric and other influences. The question of preserving them is not merely one of finance, but, especially in the case of railroads, one affecting the lives and property of a large portion of the community. What, then, is the best method of preserving them?

The almost universal method is by means of paints, or the application of substances to their surfaces which will resist or retard the influence of air, water, and other destructive agencies. The requisites of a good paint for this purpose are that it shall adhere firmly to the surface, and not chip or peel off, thereby leaving portions of the surface exposed. It must not corrode the iron, else the remedy may only aggravate the disease. It must form a surface hard enough to resist influences which would remove it by friction, yet elastic enough to conform to the expansion and contraction of the metal by heat and cold. It must be impervious to and unaffected, as far as possible, by moisture, atmospheric and other influences to which the structure may be exposed.

The paints that have been used for this purpose are principally asphalt and coal-tar paints, consisting of mineral and artificial asphalt or coal-tar, either applied alone or combined with each other, and, more or less, with metallic bases, and iron oxide paints and lead oxide paints, especially red lead, in all of which the pigment is held to the surface of the iron or steel by combination with linseed oil. The choice of paints must lie, so far as our present practical experience goes, between these three classes, zinc oxide being found to be entirely unsuitable on account of a propensity to peel off. What, then, is found to be the experience in actual practice with these? Asphalt and coal-tar paints “run” when exposed to the sun and other sources of heat, which is a serious matter with vertical surfaces; and after a time become extremely brittle and scale off entirely, leaving the under surface exposed, unless the paint is constantly renewed. In the meantime the exposed iron and steel are being corroded by rust. Iron oxide paints, including “metallic brown,” are paints made from iron ore, or by some chemical process with an iron base. These are invariably iron in a greater or less degree of oxidation, or in other words, rusted iron. Now it is well known that one of the most active promoters of rust or decay in iron is the rust itself. Under the combined influences of the moisture and carbonic acid of the atmosphere, iron oxide or iron rust becomes a carrier of oxygen from the air to the metal, rust begetting rust. It is therefore evident that this material alone has no preserving effect on iron; in fact, it promoted its decay.

How is it when combined with linseed oil in the form of paint? In the economy of nature, iron oxide is a great disinfectant. When in contact with organic matter and moisture, even at a low temperature, under favourable conditions, it readily gives up oxygen, destroying more or less the organic matter, and being itself reduced to a lower oxide. When thus reduced, with equal readiness it absorbs oxygen from the atmosphere, and again passes it on, thereby promoting and eventually ensuring the destruction or transformation of the organic matter with which it may be in contact, either in the soil or elsewhere. The same process appears to take place when combined with linseed oil in the form of paint and exposed to atmospheric influences, the oil being the organic matter. If linseed oil in drying formed an air-and water-proof film, it might be urged that the oxide of iron would be entirely protected from the direct influences of oxygen of the air and moisture. Such however is not the case.

The most eminent authorities have recently shown that the dried film of linseed oil, unless united with a pigment that combines chemically and forms a water-proof coating with it, actually absorbs water very much like a sponge. Where water will go air will also go, and we thus have in direct contact with the iron oxide of the paint, which does not combine chemically with oil, those elements, air, moisture, and organic matter, which cause the iron to become a carrier of oxygen and a destroyer of what it is in contact with. It is well known that iron paint darkens with age; this is caused largely by the iron oxide losing oxygen, which is partly transferred to the oil, burning it up and destroying its tenacity, as may be seen by examining iron structures painted for some time with iron paint or metallic brown, the paint being found extremely brittle and in feathery scales. This is not all the damage that is done. The iron oxide in the paint becomes a carrier of oxygen to the very metal it was designed to protect, and the process of corrosion is commenced and carried on under the paint, which eventually peels or scales off, the surface of the metal being found more or less oxidised and corroded.

Asphalt and iron oxide being thus shown to be entirely incapable of preserving the iron, it remains for us to consider the effect of red lead. This pigment has the property of forming with linseed oil a hard elastic coating, clinging with great tenacity to the metal. It has no oxidising effect on iron, and does not act as a carrier of oxygen from the atmosphere after the paint has set, neither does it render the oil brittle nor promote rust. When red lead fails, it is principally by gradual wear or friction from the outside. It does not scale or blister, which both asphalt and iron oxide paints will do, thereby requiring a thorough scraping and removal of old material before a new coat can be applied. Any red lead pigment adhering to the metal forms a permanent base for subsequent paintings, and is utilised in further preserving the metal. The U.S. Government specifications for ironwork in the new Library Building of Congress provide that “all the work not Bower-Barffed must be given one coat of pure red lead paint—not metallic paint of any kind, but pure red lead—before leaving the shop and becoming rusted.”

The experiments of the U.S. Navy Department on the preservation and fouling of plates covered with different pigments may be interesting. A plate of iron covered with asphalt paint was immersed in sea-water for eight months and six days at the U.S. Navy Yard, Portsmouth, N.H. At the end of that period it was found to be covered with scum and mud, and very badly rusted. A plate coated with iron paint, immersed at Key West, Fla., was found to be covered with branch shell and coral, but little paint remaining, and very badly pitted and rusted. A plate with two coats of red lead, at the Norfolk Navy Yard, was found to have a few barnacles attached, but to be in fair condition, with no rust whatever on the iron after the paint was removed. It will be seen that not only did the red lead protect the iron better than the other pigments referred to, but that the plates were in far better condition as regards barnacles and fouling. The superiority of red lead being thus established, it is adopted for use on hulls of U.S. Government warships.

On the Dutch State railroads a series of experiments extending over a period of three years were made with the above pigments on scrubbed plates, as well as those which had been pickled in acid to remove the scale. It was found that the red lead was superior in each case to the others.

If red lead is thus proved to be the best pigment for preserving iron and steel structures, what is the proper method for applying it? We have seen above that the value of red lead depends upon its forming certain combinations with the oil, and actually setting very much the same as plaster of Paris or cement sets when mixed with water. To successfully work with the latter substances, it is necessary to put them in shape as quickly as possible after mixing with water before the setting takes place. If the chemical action of setting has partly taken place, the material may be moulded, but it is known that good results will not be obtained. Red lead, like these substances, must be applied to the work before it sets with the oil. It is on this point that failures in the use of pigment have generally occurred, because if it be applied after the combining or setting process has taken place, the hard, elastic, clinging coating will not be formed on the iron surface.

The following is the practice of one of the largest shipbuilding establishments in applying red lead to the hulls of vessels. The plates are first pickled in a dilute solution of muriatic acid; then passed between rapidly revolving wire brushes, which remove all scale and dirt, leaving the iron with a bright, smooth surface; then thoroughly washed with pure water, and rubbed entirely dry; and immediately coated with red lead and pure raw linseed oil. The red lead is first thoroughly mixed with just enough linseed oil to form a very thick, tough paste, which will keep for several days without hardening. This paste, as wanted for use, is thinned down to the proper consistency for spreading with pure linseed oil, and applied at once, care being taken to leave paint-pots empty at night. A gallon of paint thus prepared contains about 5 lb. of oil and 18 lb. of red lead, and will cover on first coat about 500 square feet. In this way the red lead and oil get their initial set on the surface of the iron, and the closer the pigment is brought to the iron the more durable will it be found. Some parties prime iron with iron oxide paint or metallic brown before applying red lead, which appears to be a mistake, as this paint readily scales from iron, and, of course, carries the lead with it. Others coat the iron with oil before applying the red lead. This, too, prevents the adhering paint from coming in contact directly with the surface, and should be avoided, provided the iron is properly prepared by thorough cleaning and removal of any scale and moisture, which is a matter of the greatest importance.

In priming wood surfaces which are absorbent of oil, the best practice favours the putting on of a coat of pure oil, or oil thinned with turpentine, which shall penetrate the surface, and form a binder for the subsequent coats. With iron, the case is quite different, provided we have a paint which, from its very nature, can attach itself firmly to the surface, because it is out of the question for it to hold on to the surface of iron by any process of absorption into the pores of the metal, as linseed oil will not penetrate to any extent. Such a paint should be put directly on the surface of the clean, dry metal, as is done in the cases of Government vessels referred to, without the intervention of a coat of oil or other substances.

The rusting of iron before the application of paint, which is sometimes recommended, should by all means be avoided, as it not only prevents the contact of the paint with the metal, but induces a chemical action which may go on with its corroding work under the applied paint.

As to the relative cost of iron oxide paints and red lead, there is no doubt that the first cost of painting structures with iron oxide is somewhat less than with red lead. The best railroad authorities state, however, that labour in painting structural work costs twice as much as material. The true economy must therefore be sought in the durability of the paint as well as the preservation of the structure from rust. Actual experiments have shown that structures painted with iron paint had to be repainted in the third or fourth year, those with red lead not until the sixth year.

In the second painting with iron paint, the old material must be entirely removed before a fresh coat can be properly applied, entailing considerable increased cost, whereas with the red lead no such expense is necessary, but, as before stated, a portion of the pigment remains on the iron, continuing to protect the surface, and is the very best base for the new coat, besides contributing materially towards it, lessening the expense of each repainting. It will therefore be easily seen that, although in first cost red lead may be slightly dearer than the iron paint, yet in the long run it will be greatly cheaper, besides giving assurance, for the reasons above stated, that the structure is not deteriorating from the effects of the atmosphere and paint.

Before closing, it might be well to allude to the effect of lampblack when mixed in small quantities, say an ounce to the pound of red lead. It changes the colour to a deep chocolate, a possible advantage in some cases, and also prevents the red lead from taking its initial set with linseed oil as quickly as when mixed with oil alone. Experiments recently made showed that this compound would remain mixed in paste form with linseed oil some thirty days without hardening. Thorough mixture is of the greatest importance, and should be done in the dry state before adding the oil. If rapid drying is desired, Japan dryer can be mixed with the oil used in thinning the paste before application with the brush.

Too much stress cannot be laid on the great importance of having the metallic surface perfectly clean and as free as possible from scale and rust before the application of the paint. Where pickling with acid is impracticable, as is frequently the case in railroad and other structural work, thorough brushing with wire brushes should be resorted to.

Fresco Painting.—The following observations are due to Prof. Barff, who dealt with the subject in one of the Cantor Lectures given at the Society of Arts.

The ground upon which fresco is painted is a lime ground; and in order to have a permanent picture, it is clear we must have a firm and stable ground. In order to prepare that ground, first of all the wall must be absolutely dry; there must be no leakage of moisture from behind. Lime which has been “run” (as it is technically called by builders) for a year or a year and a half is best to be employed, for in proportion as the lime has been carbonated (though it must not be so to too great an extent) by the action of the carbonic acid of the air it makes a better and a harder mortar. With this lime must be mixed sand, and a great deal depends on the selection of the sand. It must be river sand, and it should be of even grain; the sand should be mixed with water, and allowed to pass along down a small stream, so that in the centre of the stream you would have sand grains pretty nearly equal in size. This is a point of considerable importance. The reason why new lime cannot and ought not to be used is because it blisters; small blisters appear on the surface, and that of course would be ruinous to a picture. A well-plastered wall should not have a blister or crack in it, and this is secured by having your lime run for some time, of good quality to start with, and mixed with good sand. There is no chemical process that takes place in fresco painting other than this, that silicates are formed by the action of the lime upon the sand, and carbonates by the action of the carbonic acid of the air upon the lime.

In painting a fresco picture, inasmuch as there is no retouching the work when it is finished, the artist must make his drawing very carefully. The cartoon is made upon ordinary paper, then it is fixed against the wall where the picture is to be painted. The part where the artist decides to begin his work is uncovered, that is to say, a portion of the paper is turned down and cut away, but in such a manner that it may be replaced. Then the plasterer puts fresh plaster, about an eighth of an inch thick, upon the uncovered portion of the wall, and the plasterer’s work is of the utmost importance in fresco painting. The workman ought to practise it well before he attempts to prepare the ground for a large picture, and it is of the greatest importance to allow the man to practise for several weeks before he is allowed to prepare any portion of the ground, even for decorative: painting. In this way he becomes accustomed to the suction of the wall, and upon the suction of the wall depends the soundness of the ground and the success of fresco painting.

When the plaster is first put on, of course it is very soft; the piece of cartoon is replaced upon it, and the lines of the picture are gone over with a bone point, so that an indentation is made, and then the artist begins his painting. At first he finds his colours work greasy; you cannot get the tint to lie on, it works streaky; but you must not mind that, you must paint on, but you must only paint on for a certain time, for if you go on painting too long you will interfere with the satisfactory suction of the ground, which is so necessary to produce a good fresco painting. Of course, nothing but practice can tell any one the period at which he ought to stop. After some practice, you know perfectly well by the feel when you ought to stop. If you feel your colour flowing from your brush too readily, you ought to stop at this period. You must then leave your work for a time, and go back to it again. And then you will find, as the plaster sucks in the colour which you have first laid on, that there will be—it may be in the course of half-an-hour, it may be an hour, that depends upon the temperature of the atmosphere—a pleasant suction from your brush, the colour going from it agreeably, and you will find that it will cover better. Now is the time to paint rapidly, and complete the work you have in hand. When the colour leaves your brush as though the wall was thirsty for moisture, you should cease painting; every touch that is applied after that will turn out grey when it dries, and the colour will not be fast upon the wall.

You will see, then, how impossible it is, with such materials, to paint in the same style in which you paint a picture in oil-colour. Fresco painting involves the adoption of an entirely different style from oil painting. The frescoes of the old masters are not highly wrought up, highly-finished works. They depend for their effect upon the juxtaposition of tints, the shadows being intensified by lines and cross-hatching. If you look at those reproductions of some of the most valuable fresco paintings of the old masters, you will see the method adopted by them depended upon the juxtaposition of tints, not upon covering over, and over, and over again. That juxtaposition of tints produces roundness, transparency, and has a very pleasing effect upon the eye. If two tints are put against one another, they do not appear to us as if they were single, but each adds something to the effect of the other, and together they produce a pleasurable and agreeable effect, if they have been properly selected. We all know how tempting it is to go back to a piece of painting and do something to it that ought to have been done before. We think that a touch will improve it, and we go and make it: but in fresco painting the temptation must be resisted, for it will be absolutely fatal to the permanency of the work.