Alexander Watt

MISCELLANEOUS PAPERS.

Waterproof Paper.—Scoffern and Tidcombe's process.—Dr. Wright's process for preparing Cupro-Ammonium.—Jouglet's process.—Waterproof Composition for Paper.—Toughening Paper.—Morfit's process.—Transparent Paper.—Tracing Paper.—Varnished Paper.—Oiled Paper.—Lithographic Paper.—Cork Paper.—New Japanese Paper.—Blotting Paper.—Parchment Paper.—Test Papers.

Waterproof Paper.—Scoffern and Tidcombe's Process.—In this process, for which a patent was granted in 1875, the well-known solubility of cellulose in cupro-ammonium is taken advantage of, for the purpose of producing waterproof paper by destroying its absorptive properties. After the paper is made and dried in the usual way by the paper-making machine, it is led through a bath of cupro-ammonium, having a roll or rollers therein, or in connection therewith, either on reels on which the paper is reeled, or from the continuous web of paper itself directly from the machine, and from this bath it is led over a table of wire-cloth, or india-rubber, or over a series of rollers forming a table, under which steam-pipes are placed for the purpose of "setting," or partially drying, the web; it is then led over suitable reels in a hot-air chamber to season or finish the treated paper, which is then cut as the paper runs, by the ordinary cutting machine, into the required sheets. The chamber in which the paper is treated is ventilated as follows:—Over the bath and hot-air chamber is another chamber having openings leading into the hot-air chamber, and at these openings a steam-blast, or fan-blast, is applied, which ventilates the chamber in which the paper is heated, and drives the ammonia into contact with either sulphurous or hydrochloric acid, and by this means the ammonia is recovered in a solid form which would otherwise be wasted.

The inventors also incorporate hydrated oxide of copper with paper pulp, so that after it is made into paper it has only to be subjected to the action of ammonia, as ordinarily done, or to the action of gaseous ammonia mingled with steam. Brown papers are strengthened and glazed by passing them through a bath of pulp containing cupro-ammonium, either with or without pitch, tar, or other resinous matters. It is well known that by passing paper through a cupro-ammonium bath it is surface dissolved and glazed by its own material, and if it be desired to unite two or more sheets together this is the most economical way of conducting the operation; but if it be desired to strengthen and glaze a single thickness of paper or millboard, it is considered undesirable to make the glaze by dissolving a portion of the paper itself. In this case the inventors pass the web or sheet of paper through a bath, not of cupro-ammonium simply, but of cupro-ammonium in which ligneous material is already dissolved; and when the glazing of brown paper is to be effected, they prefer to fortify the bath with tar, pitch, marine glue, or other resinous materials. By this process, panels and tiles may be manufactured from millboard, or thick sheets of ligneous material made from pulp already incorporated with hydrated oxide of copper. The panels, etc., are passed, by means of an endless web, through a bath of ammoniacal solution, or the vapour of ammonia and steam, and the tiles or panels may be surface-glazed by exposing them while moist to the action of fluo-silicic acid gas, by which silica is deposited in the material and on its surface.

Dr. Wright's Process for preparing Cupro-ammonium.—This process, which has been adopted at the Willesden Paper Mills, may be thus briefly described:—In the first part of the process, metallic copper, in small lumps, solid metal, or clippings, etc., is covered with a solution of ammonia in water, or with a weak solution of cupro-ammonium hydrate, containing an amount of free ammonia in solution dependent upon the strength of the copper solution ultimately required; a current of air is then caused to pass through the whole by means of an air-pump, in such a manner that the bubbles of air pass over and amongst the fragments of metallic copper, which, if in small particles, may be advantageously kept in suspension by any convenient agitator. In a few hours the liquid becomes saturated with as much copper as it can dissolve, the rate of solution varying with the form of the vessel containing the materials, the strength of the ammoniacal fluid, and the rate of the passage of the stream of air. To carry this process into effect, metallic copper in fragments of convenient size is loosely piled inside a vertical tube or tower, and water is allowed to trickle from a pipe over the copper so as to keep its surface moist. At the base of the tower a current of air, mixed with ammonia gas, is caused to pass into the tower, so as to ascend upwards, meeting the descending water as it trickles over the copper. Under these conditions the copper becomes oxidised, and the water dissolves firstly the ammonia gas, and, secondly, the oxide of copper formed, so that the liquor which passes out at the base of the tower is a solution of cupro-ammonium hydrate, the strength of which depends on the proportions subsisting between the bulk of the mass of copper, the quantity of water trickling over it, and the amount of air and ammonia gas supplied in a given time. As an example of the method of carrying out the above process, the inventor proceeds as follows:—He constructs a vertical iron tower which may be ten inches in internal diameter and ten feet in height, and this is filled with scraps of sheet copper. On this water is allowed to trickle, whilst at the base of the tower a mixture of air and gaseous ammonia is allowed to pass upwards through the tower, by which a solution of cupro-ammonium is formed, which is allowed to trickle out at the base of the tower into a tank. It has been found advantageous to use a series of towers, allowing the air and ammonia gas that pass out at the top of the first tower to enter at the bottom of the second tower, and so on successively throughout the series. The weaker solutions produced in the later towers of the series are used instead of water in the earlier towers, so that practically all the ammonia gas originally used is obtained in the form of cupro-ammonium hydrate solution, issuing from the first tower of the series.

The cupro-ammonium process, as carried on at the Willesden Mills, is applied to ropes, netting, etc., by immersing them in a solution of cupro-ammonium, which, when they are subsequently dried, gives them a varnished appearance, while at the same time, the fibres having become cemented together by the action of the cupro-ammonium, their strength is increased. By the same process paper, canvas, and other manufactured articles are rendered waterproof. A concentrated solution of cupro-ammonium may also be used for securing envelopes, whereby the adhesion of the surfaces of the paper is rendered perfect, and the only means of opening the envelope is by cutting or tearing the paper.

Jouglet's Process.—This process, which with modifications has been adopted by others, is based on the solvent action on cellulose of a solution of oxide of copper in ammonia. A quantity of this solution is placed in a tank, and the paper rapidly passed over and in contact with the surface of the liquid, by means of suitable rollers in motion. The paper is afterwards pressed between a pair of rolls and dried by the ordinary drying cylinders. The brief contact of the paper with the liquid occasions just sufficient action on the cellulose to have the effect of an impermeable varnish.

Waterproof Composition for Paper.—The following composition for rendering paper waterproof for roofing and flooring purposes has been patented in America.[29] By preference good, hard manilla paper is selected, and a composition of the following ingredients is applied with a brush, or by means of rollers:—Glue, 2 lbs., is dissolved in 3 gallons of crude petroleum, of about the density of 33° B. at 60° F.; 35 gallons of resin oil, and about half a pint of oil of eucalyptus, which will have the effect of destroying the objectionable odour of the resin oil. To this mixture is further added about 4 gallons of any ordinary drier. The above ingredients are to be thoroughly mixed by agitation, and the composition brushed over the paper in a room heated to about 80° F., and allowed to dry. It is said that paper thus coated will exclude wind, cold, dampness, and dust.

Toughening Paper.—Morfit's Process.—The object of the following process is to produce a paper "toughened in a degree and quality distinctively from any other in the market," and is applicable to all kinds of paper, but more particularly to those made with inferior grades of pulp for printing newspapers, and for wrapping papers. The means employed are the seaweeds which form glutinous liquors with water, such as Carrageen, or Irish moss, Agar-agar, and the like. Any of such seaweeds may be employed, either separately or mixed with another of its kind, according to the judgment of the operator and the sort of paper to be manufactured, but some seaweeds are superior to others for this purpose. The raw seaweed is first washed, and then boiled with water until all the soluble matter has been extracted, and the resulting liquor is then strained. The hot strained liquor forms the bath in which sheets of paper or pulp are to be treated. If desired, resin soap and aluminous cake may be added to the glutinous liquor, but these "serve rather to size and make the paper rustle than increase its toughness." If the paper is to be treated in the form of sheets or web, it is to be passed, as it leaves the wire-cloth in which it is formed, through a hot solution of the seaweed alone, or mixed with resinous soap and aluminous cake, and dried by means of suitable machinery. To apply it to the pulp, the latter is to be diffused in the hot liquor, and the sheets or web made therefrom in the usual manner. The proper proportions of seaweed, resinous soap, and aluminous cake will vary with the kind of pulp and sheets under treatment, and must be adjusted as the judgment of the operator determines best for each operation.

Transparent Paper.—There are several methods of rendering paper transparent, amongst which the following has been recommended:—

The above ingredients are placed in an iron or other suitable vessel, in which they are thoroughly mixed, and the whole then boiled for about eight hours. The mixture is then allowed to cool, when it is again well stirred and the following substances added:—White copal, 30 parts; gum sandarac, 2 parts, these ingredients being well incorporated by stirring.

Tracing Paper.—Sheets of smooth unsized paper are laid flat on a table, and then carefully coated on one side only with a varnish composed of Canada balsam and oil of turpentine. The brush used for this purpose must be a clean sash tool, and when the first sheet has been varnished in this way it is to be hung across a line to dry. The operation is then to be applied to fresh sheets in succession until the required quantity of paper has been treated. In the event of one coating of the varnish not rendering the paper sufficiently transparent, a second coating may be applied when the first coating has become quite dry.

Varnished Paper.—When it is desired to varnish the surface of paper, card-work, pasteboard, etc., it must first be rendered non-absorbent with two or three coatings of size, which will also prevent the varnish from acting upon any colour or design which may be impressed upon the paper. The size may be made by dissolving isinglass in boiling water, or by boiling clean parchment cuttings in water until a clear solution is formed, which, after straining, is ready for use. If necessary, for very delicate purposes, the size thus prepared may be clarified with a little white of egg. The size should be applied, as in the former case, with a clean sash tool, but the touch should be light, especially for the first coating, lest the inks or colours should run or become bleared. When dry, the varnish may be applied in the usual way.

Oiled Paper.—Sheets of paper are brushed over with boiled linseed oil, and then hung up to dry. Paper thus prepared is waterproof, and has been used as a substitute for bladder and gut skins for covering jam pots, etc., but the introduction of parchment paper has almost entirely superseded it.

Lithographic Paper.—This paper, which is written upon with lithographic ink, may be prepared by either of the following formulÆ:—1. Take starch, 6 ozs.; gum arabic, 2 ozs.; alum, 1 oz. Make a strong solution of each separately in hot water, then mix the whole and strain the liquor through gauze. It must be applied to one side of the paper while still warm by means of a soft brush or sponge; a second or third coating may be given as the preceding one becomes dry. The paper is finally pressed to render it smooth. 2. The paper must first receive three coats of thin size, one coat of good white starch, and one coat of a weak solution of gamboge in water. The ingredients are to be applied cold with a sponge, and each coat allowed to dry before the next is applied.

Cork Paper.—A paper under this title was patented in America by Messrs. H. Felt and Co.; it is prepared by coating one side of a thick, soft, and flexible paper with a mixture composed of glue, 20; gelatine, 1; and molasses, 3 parts, and covering with finely-powdered cork, which is afterwards lightly rolled in. The paper thus prepared is said to be used for packing bottles.

New Japanese Paper.—According to the Bulletin du MusÉe Commercial, a native of Japan has recently invented a new process by which paper may be made from seaweed. The paper thus made is said to be very strong, almost untearable, and is sufficiently transparent to admit of its being used as a substitute for window glass; it takes all colours well, and in many respects resembles old window glass.—Board of Trade Journal.

Blotting Paper.—This paper, requiring to be very absorbent, is not sized, but is prepared with starch alone, which, while holding the fibres together, does not affect the absorbent property of the paper. Dunbar gives a recipe for making blotting paper which has been found successful, and from which we make a few extracts. In selecting materials for blotting, of high-class, cotton rags of the weakest and tenderest description procurable should be chosen. Boil them with 4 lbs. of caustic soda to the cwt.—that is, if you have no facilities for boiling them in lime alone. When furnished to the breaking-engine, wash the rags thoroughly before letting down the roll; when this is done, reduce them to half-stuff, and as soon as possible convey them to the potcher. When up to the desired colour, drain immediately. The breaker-plate should be sharp for blottings, and the beater-roll and plate also in good order, and the stuff beaten smartly for not more than an hour and a half in the engine. For pink blottings furnish two-thirds white cottons and one-third of Turkey reds if they can be got, or dye with cochineal to desired shade; empty down to the machine before starting, and see that the vacuum pumps are in good condition. Remove weights from couch-roll, and if there are lifting screws raise the top couch-roll a little. Take shake-belt off, as the shake will not be required. Press light with first press, and have the top roll of the second press covered with an ordinary jacket similar to couch-roll jacket. Dry hard, and pass through one calender with weights off, and roll as light as possible, just enough to smooth slightly.

Parchment Paper.—This paper, which is extensively used for covering jars and pots for pickles and jams, is prepared, according to the process of PoumarÈde and Figuier, as follows:—White unsized paper is dipped for half a minute in strong sulphuric acid, specific gravity 1·842, and afterwards in water containing a little ammonia. By Gaine's process (1857) unsized paper is plunged for a few seconds into sulphuric acid diluted with half to a quarter of its bulk of water (the acid being added to the water), and the solution allowed to cool until of the same temperature as the air. The paper is afterwards washed with weak ammonia. This process, which has been extensively worked by Messrs. De la Rue and Co., produces a far better material than the foregoing.

Mill and Card-board.—In the manufacture of boards refuse materials of all kinds that occur in the paper-mill may be used, and these are sorted according to the quality of boards for which they are best suited. After being well beaten the resulting mass is mixed with suitable proportions of rag pulp, kaolin, chalk, white clays, &c. There are four principal processes by which boards are manufactured, namely,

1. By superposing several sheets of paper and causing them to unite by a sizing material.

2. By superposing several wet leaves at the time of couching.

3. By moulds provided with thick deckles.

4. By special machines similar to those used for making continuous webs of paper, but without a drying cylinder, the sheets being dried in the open air or in a heated room.

The third method is only adopted for boards of moderate thickness, as an excess of pulp would render the draining difficult.

Making Paper or Cardboard with two Faces by Ordinary Machine.—By this process, recently patented by Mr. A. Diana, all kinds of thin or thick paper or cardboard are manufactured with two different faces by means of the ordinary paper-machine, having a single flat table with a single wire-gauze web, without requiring a second metallic web. For this purpose the two pulps are prepared separately, and one is caused to pass on to the web in an almost liquid condition; this is allowed to drain off sufficiently, and the second pulp (also in a liquid condition) is then passed uniformly upon the whole surface of the previous layer. The water drains off from this layer through the first layer, and the paper or cardboard is thus directly formed with two different faces, the subsequent operations being as ordinarily employed in paper-making. The space between two of the suction cases employed for drawing off the water in the pulp is a suitable point for the distribution of the diluted second pulp, which is almost liquid.

Test Papers.—These papers, which are extensively used both in the laboratory and the factory, for determining the presence of acids or alkalies in various liquids, may be prepared as follows:—Litmus paper, for detecting the presence of acids, is prepared by first making an infusion of litmus. Reduce to a paste with a pestle and mortar 1 oz. of litmus, adding a little boiling water; then add more boiling water—from 3 to 4 ozs. in all—and put the mixture into a flask and boil for a few minutes; finally, add more boiling water to make up half a pint, and when cold filter the liquor. To prepare the test paper, a sufficient quantity of the liquid being poured into a flat dish, pieces of unsized paper are steeped in the blue liquid, so that all surfaces may be thoroughly wetted; the paper is then to be hung up by one corner to drain, and afterwards dried. As many sheets of paper as may be required should be treated in this way, and the sheets afterwards cut up into convenient strips for use. Red litmus paper, for detecting slight traces of alkali in liquids, may be prepared by dipping a glass rod, previously dipped into a very dilute solution of sulphuric acid, into one-half of the above infusion, repeating the operation cautiously until the liquid turns from blue to a slightly red tint. Unsized paper when dipped in this will acquire a reddish colour which is very sensitive to the action of weak alkaline liquors, and the vapour of ammonia restores the blue colour instantly. Turmeric paper is prepared by dipping unsized paper in a decoction of turmeric—about 2 ozs. to the pint. Paper steeped in this solution and dried acquires a yellow colour, which turns brown in alkaline solutions.