Part 316

«Black.—A Permanent Black of Rich Luster for Metal Boxes.»—Dissolve chlorate of potassium and blue vitriol, equal parts, in 36 times as much water, and allow the solution to cool. The parts to be blacked may be either dipped in the solution, or the solution may be flowed on and allowed to remain until the metal becomes black, after which the fixtures should be rinsed in clean water and allowed to dry. Those parts of the surface which show imperfections in the black should be recoated.

«Dead White on Silver Work, etc.»—Bruise charcoal very finely and mix it with calcined borax in the proportion of 4 parts of charcoal to 1 of borax. Of this make a paste with water; apply this paste on the parts to be deadened; next expose the piece to the fire of well-lit coal until it acquires a cherry-red shade; allow to cool and then place it in water slightly acidulated with sulphuric acid. The bath must not be more than 5° Bé. Leave the piece in the bath about 2 hours, then rinse off several times.

«White Coating for Signs, etc.»—A white color for signs and articles exposed to the air is prepared as follows for the last coat: Thin so-called Dutch “stand” oil with oil of turpentine to working consistency, and grind in it equal parts of zinc white and white lead, not adding much siccative, as the white lead assists the drying considerably. If the paint is smoothed well with a badger brush, a very durable white color of great gloss is obtained. Linseed oil, or varnish which has thickened like “stand” oil by long open storing, will answer equally well.

«To Prevent Crawling of Paints.»—Probably the best method to pursue will be to take an ordinary flannel rag and carefully rub it over the work previous to varnishing, striping, or painting. This simple operation will obviate the possibility of crawling.

In some instances, however, crawling may be traced to a defective varnish. The latter, after drying evenly on a well-prepared paint surface will at times crawl, leaving small pitmarks. For this, the simple remedy consists in purchasing varnish from a reputable manufacturer.

«FIREPROOF PAINTS:»

See also Fireproofing.

Fireproofing paints of effective quality are prepared in different ways. Naturally no oily or greasy substances enter into their composition, the blending agent being simply water.

I.—One of the standing paints consists of 40 pounds of powdered asbestos, 10 pounds of aluminate of soda, 10 pounds of lime, and 30 pounds of silicate of soda, with the addition of any non-rosinous coloring matter desired. The whole is thoroughly mixed with enough water to produce a perfect blend and render an easy application. Two or more coats of this is the rule in applying it to any wood surface, inside or outside of building.

II.—Another formula involves the use of 40 pounds of finely ground glass, a like amount of ground porcelain, and similarly of China clay or the same quantity of powdered asbestos, and 20 pounds of quicklime. These materials are ground very fine and then mixed in 60 pounds of liquid silicate of soda with water, as in the preceding formula. Two or more coats, if necessary, are given.

Each of these paints is applied with a brush in the ordinary way, the drying being accomplished in a few hours, and, if coloring matter is desired, the above proportions are varied accordingly.

III.—A surface coated with 3 coats of water glass, these 3 coats being {491} subsequently coated with water glass containing enough whiting or ground chalk to make it a trifle thicker than ordinary paint, is practically non-inflammable, only yielding to fierce consuming flames after a somewhat protracted exposure.

IV.—Zinc white, 70 pounds; air-slaked lime, 39 pounds; white lead, 50 pounds; sulphate of zinc, 10 pounds; silicate of soda, 7 gallons. The zinc white and lime are mixed together, then ground in elastic oil, after which the silicate of soda is added, this addition being followed by the white lead and sulphate of zinc. This white paint can be colored to meet any desired shade and it may be classed as a good working paint and probably fireproof to the same extent that most of the pretentiously sounded pigments on the markets are.

«Fireproof and Waterproof Paints.»—The following recipes are claimed to resist both fire and water: A preparation for protecting wood against the action of fire and of moisture, and also for producing on the surface of wood and metal a coat, insulating with reference to electricity and preservative from corrosion, has been introduced in France by Louis Bethisy and Myrthil Rose. The bases or fundamental raw materials quite distinct from those hitherto employed for the same purpose, are 100 parts, by weight, of nitro-cellulose and 30 parts, by weight, of chloride of lime, dissolved in 50 per cent alcohol.

Preparation of the Bases.—The cellulose (of wood, paper, cotton, linen, ramie, or hemp) is put in contact with two-thirds part of sulphuric acid of 66° Bé. and one-third part of nitric acid of 42° Bé. for some 20 or 30 minutes, washed with plenty of water, and kept for 24 hours in a tank of water supplied with an energetic current.

The nitro-cellulose thus obtained is bleached for this purpose; a double hypochlorite of aluminum and magnesium is employed. This is obtained by grinding together 100 parts of chloride of lime, 60 parts of aluminum sulphate, 23 parts of magnesium sulphate, with 200 parts of water.

When the nitro-cellulose is bleached and rewashed, it is reduced to powder and dried as thoroughly as possible. It is then placed in a vat hermetically closed and put in contact with the indicated proportion of calcium chloride dissolved in alcohol. This solution of calcium chloride should be prepared at least 24 hours in advance and filtered.

Composition of the Coating.—This has the following constituents: Bases (nitro-cellulose and solution of calcium chloride), 1 part; amyl acetate (solvent of the bases), 5 parts, by weight; sulphuric ether of 65°, 1.650 parts, by weight; alcohol, 0.850 parts, by weight; one of these powders, alum, talc, asbestos, or mica, 0.100 parts. Other solvents may be employed instead of amyl acetate; for example, acetone, acetic acid, ether alcohol, or methylic alcohol. The ether alcohol furnishes a product drying very quickly. If a very pliant coating is desired, the amyl acetate is employed preferably, with addition of vaseline oil, 0.20 parts, and lavender oil, 0.010 parts.

Method of Operating.—The sulphuric acid is mixed with the alcohol, and left for an hour in contact, shaking from time to time. Afterwards the amyl acetate is added, and left in contact for another hour under similar agitation. In case of the employment of vaseline oil and lavender oil, these two are mingled in ether alcohol. The base is introduced and left in contact for 24 hours, with frequent agitation. The fluidity of the product is augmented by increasing the quantity of the solvent.

Properties.—Wood covered with this coating is fireproof, non-hygrometric, and refractory to the electric current. It also resists the action of acids and alkalies. Metals covered with it are sheltered from oxidation, and effectually insulated on their surface from the electric current. The coating is liquid in form, and applied like collodions, either by the brush or by immersion or other suitable method.

«Paint Deadening.»—In order to obtain an even dullness of large walls, proceed as follows: After all the dirt has been carefully swept off, oil with 2 parts linseed oil and 1 part turpentine and rub down the smooth places in the wet oil with pumice stone. When the oil coating is dry, mix the ground paint, consisting of whiting, 2 parts; and white lead, 1 part; both finely ground and diluted as above. Do not apply the grounding too thin, because the chalk in itself possesses little covering power. It is not the mission of the chalk, however, to adulterate the material, but to afford a hard foundation for the subsequent coats. For the third coating take white lead, 1 part; and zinc white, 1 part; thin as above and blend with a soft hair pencil. For the final application use only zinc white, ground stiff in oil with any desired mixing color and thinned with turpentine and rain water. Mix the {492} water and the turpentine with the color at the same time, and this coat may be dabbed instead of blended. By the addition of water the paint becomes dull more slowly and is a little more difficult to lay on; but it does not show a trace of gloss after a few days and never turns yellow, even in places less exposed to the air, and besides excels by great permanency.

Another way is to add white wax instead of water to the last coating. This wax paint also gives a handsome dullness but is more difficult of treatment. A nice matt coating is also obtained by addition of Venetian soap, dissolved in water instead of the wax. This is very desirable for church decorations where exceptionally large surfaces are to be deadened.

«PAINT DRYERS:»

I.—Ordinary barytes 25 pounds Whiting 4 pounds Litharge 2 pounds Sulphate of zinc 2 pounds Sugar of lead 2 pounds Boiled linseed oil 5 pounds Plaster of Paris 1⁠/⁠2 pound

II.—Whiting 16 pounds Barytes 16 pounds White lead 3 pounds Boiled linseed oil 3⁠/⁠4 gallon

«PAINTS FOR GOLD AND GILDING:»

«Gold Paints.»—The formulas of the various gold paints on the market are carefully guarded trade secrets. Essentially they consist of a bronze powder mixed with a varnish. The best bronze powder for the purpose is what is known in the trade as “French flake,” a deep gold bronze. This bronze, as seen under the microscope, consists of tiny flakes or spangles of the bronze metal. As each minute flake forms a facet for the reflection of color, the paint made with it is much more brilliant than that prepared from finely powdered bronze.

For making gold paint like the so-called “washable gold enamel” that is sold by the manufacturers at the present time, it is necessary to mix a celluloid varnish with the French flake bronze powder. This varnish is made by dissolving transparent celluloid in amyl acetate in the proportion of about 5 per cent of celluloid.