(I) It is a well-known fact that cellulose is soluble in cuprous ammonia solution; paper, linen, and other vegetable tissues laid therein undergo a sort of surface-amalgamation of the fibres, which alters their absorbent powers. A sheet of paper so treated, and dried afterwards, becomes impermeable to water, and this property is not effaced by subsequent boiling. Sheets of paper soaked in the solution and laid one upon the other and rolled, become amalgamated into a kind of cardboard, possessing great elasticity and cohesive power. The cuprous solution may be prepared by agitating copper filings in a closed vessel containing liquid ammonia of 0.88 sp. gr.

(2) Dissolve 8 oz. alum and 3 3/4 oz. Castile soap in 4 pints water, and 2 oz. gum arabic and 4 oz. glue, separately, in 4 pints water; mix the solutions, heat slightly, dip in the single sheets, and hang up until dry.

(3) Waterproofing pasteboard may be effected with a mixture of 4 parts slaked lime in 3 of skimmed milk, with a little alum added. As soon as mixed, the pasteboard is brushed over with 2 successive coatings of the preparation, and thus becomes impervious to water.

(4) Take pale shellac, 5 oz.; borax, 1 oz.; water, 1 pint. Digest at nearly the boiling-point till dissolved, then strain. This forms also an excellent vehicle for water-colours, inks, etc If required quite transparent, the lac should be bleached as follows: Dissolve shellac in a lye of pearl-ash, by boiling; filter and pass an excess of chlorine gas through the solution, which will precipitate the white lac. Wash and dry the precipitate, and cast it if desired into sticks.

(5) To make waterproof packing paper, dissolve 1 3/4 lb. white soap in 1 qt. water. In another quart of water dissolve 1 1/2 oz. gum arabic and 5 oz. glue. Mix the 2 solutions, warm them, soak the paper in the liquid, and pass it between rollers, or simply hang up to dry.

(6) Even old newspapers may be converted into waterproof roofing material by applying coats of hot coal tar with a brush, uniting 2 or more thicknesses.

(7) Rendering paper impervious to grease and water. Parchment-paper is plunged into a warm solution of concentrated gelatine, to which has been added 2 1/2-3 per cent. glycerine, and allowed to dry. The resulting paper is impervious to grease. If desired to make a paper water-proof, the same parchment-paper is dipped in carbon bisulphide containing 1 per cent. linseed oil and 4 per cent. indiarubber.

(8) A strong, impervious parchment-paper is obtained by thoroughly washing woollen or cotton fabrics, so as to remove gum, starch, and other foreign bodies, then immersing them in a bath containing a small quantity of paper pulp. The latter is made to penetrate the fabric by being passed between rollers. Thus prepared, it is afterwards dipped into sulphuric acid of suitable concentration, and then repeatedly washed in a bath of aqueous ammonia until every trace of acid has been removed. Finally, it is pressed between rollers to remove the excess of liquid, dried between 2 other rollers which are covered with felt, and lastly calendered. The product is suitable for diaphragms in dialytic operations.

(9) Treat the tissue to be waterproofed with chloride, sulphate, or other soluble salt or salts of zinc or cadmium, in conjunction with ammonia, applied in the form of a solution composed of about 3 parts crystallised zinc sulphate, or 3 parts of a solution of zinc chloride at 96° Tw. (47° B.), and about 2 parts of solution of ammonia of sp. gr. 0.875. The paper which it is proposed to treat is passed through a cistern lined with lead, and specially constructed for this purpose, with an arrangement of rollers, so as to allow the material to pass through at a speed varying from 30 to 36 yd. per minute, according to the thickness. In its passage through the liquor, the material becomes perfectly saturated. From the bath it passes through a pair of squeezing rollers, which remove the superfluous liquor, and harden it by compression. From the rollers it is next passed to a suspending apparatus, then hung along the room in folds in a temperature of 110° F. (43° C), until it is sufficiently dry to be taken down.

The rollers in the cistern, the squeezing rollers, and the suspending apparatus are so speeded that the material is taken from one to the other without any inconvenience or stoppage.

(10) Treat with glue, gelatine, or other similar substances, in conjunction with bichromate or chromate of potash, soda, or alumina, applied in the form of a solution of about 1 part glue or gelatine in about 8 of water at 160° F. (71° C), and a solution of 1 part potash bichromate in 15 of water. The mode of treatment in this case differs from (9) only in 2 points. (a) During the time the material is traversing the bath, as already described, the solution is maintained at 160° F. (71° C.) by means of siphon-pipes charged with steam; (6) instead of suspending to dry, the material is immediately passed over 3 steam cylinders 7 ft. in diameter, carrying a pressure of 15-20 lb. to the sq. in. The cylinders are provided with gauges to indicate the pressure they are required to carry, and also with safety-valves to prevent this pressure from being exceeded. The bath must always be kept in a state of darkness.

(11) The paper is treated with acetate, sulphate, or chloride of alumina, applied in the form of a solution of 1 part of any of these compounds in 6 of water at 160° F. (71° C). The same conditions are required to produce a waterproof material with these compounds as those described in (9) and (10), with this difference, that it is not absolutely necessary to preserve darkness during the process.

Waterproof Paper Varnishes

(12) Pulverise 1 lb. shellac and put it into a bottle with a sufficient quantity of alcohol to cover the resin; cork the bottle tightly, and keep it in a warm place until the resin is dissolved. To 1 qt. of the liquid add 1 ok. ivory black and 1/2 oz. camphor dissolved in alcohol. Apply with a varnish brush. If too thick to work well, thin with alcohol.

(13) Johnson's green vitriol is dissolved in water, a solution of soap is added to this, and the precipitate of iron soap which is formed is collected. When this precipitate has become dry, and is then dissolved in carbon bisulphide, or in benzole, a fluid is obtained which leaves behind a waterproof layer upon paper or tissue. If the paper or tissue is to remain white, a solution of alum is used instead of that of green vitriol, and a white aluminium soap is then obtained, which is used in the same manner.

(14)Take 4 oz clean guttapercha, dissolve in 1 lb. rectified rosin oil; add 2 lb linseed oil varnish, boiling hot.

(15) 1 part dammar resin, 4 - 6 parts acetone are digested in a closed flask for 2 weeks, and the clear solution is poured off. To this 4 parts collodion are added, and the whole is allowed to clear by standing.

(16) 30 parts white shellac are digested with 500 of ether, and to the solution 15 of lead carbonate are added; it is then shaken for some time and repeatedly filtered.

(17) 5 parts glue are dissolved in 100 of warm water, and this solution is spread on paper. After drying, the paper is soaked for an hour in a 10 per cent. solution of alumina acetate and again dried, in order to give it a final glaze.

(18) 120 parts linseed oil are heated and poured into a mixture of 33 of quicklime and 22 of water, to which 55 of melted rubber have been added, stirring all the time. The varnish is strained and used hot.

(19) 1 part guttapercha is carefully digested in 40 of benzene on the water bath, and the paper is covered with it. This varnish can be drawn or written on, and it does not render the paper transparent or spotted.