A Select Collection of Valuable and Curious Arts and Interesting Experiments, / Which are Well Explained and Warranted Genuine and may be Performed Easily, Safely, and at Little Expense.

by Unknown

112. To make crayons of various colours.—Crayons or pastils consist of various coloured pigments or paints, formed into sticks or rolls for the purpose of drawing and shading with them in the manner of lead pencils. But that they may be of uniform texture or hardness, different ingredients and materials require some variation in the management. To make white crayons, nothing more is requisite than to mix superfine or refined whiting with alcohol, to the consistence of soft putty; form it into rolls of a convenient length and size and let them dry: or the whiting may be mixed with water and a sufficient quantity of burnt or calcined sulphate of lime to give the crayons a sufficient degree of hardness when dry. A great variety of elegant light colours may be formed by adding to the whiting prepared as above, small quantities of any of the coloured pigments. The most proper colors for crayons are lamp-black, prussian blue, burnt umber, burnt terra-de-sienna, red ochre, vermilion, lake, rose-pink, chrome yellow, yellow ochre and mineral green. Many other handsome greens are formed by mixing chrome yellow with prussian blue, varying the proportions; and purples are produced by mixing rose pink or lake with blue. Prussian blue and lake being each naturally of a binding nature, require only to be ground in water; but red ochre and vermilion should be ground in alcohol, or may have some quantity of the sulphate of lime mixed with them. Any of these colours may be mixed in any proportion with whiting or with each other, each compound having a sufficient proportion of the sulphate of lime, to give it a proper degree of hardness and strength when dry. The proper length for crayons is from two to three inches, and the size about the same as that of a tobacco-pipe stem. It is customary in making crayons, to have at hand a large piece of chalk with a plane surface, on which to lay the crayons as soon as they are rolled; the chalk absorbs a part of the moisture, which makes them dry the sooner and without cracking.

113. To make hard sealing wax, of various colours.—Take of gum-shellac and rosin each two ounces; and of gum-mastic one ounce; reduce them to powder and mix and melt them together over a gentle fire. Then if a red colour is required, add to the mixture one ounce of fine vermilion; for a black colour, add half an ounce of a mixture of lamp black with rum; for a blue, half an ounce of white lead with one fourth of an ounce of prussian blue; which should be previously ground together dry. To give a green colour, add finely ground verdegris; a yellow is produced by chrome yellow or gamboge; and white, by adding pure white lead to the mixture. When the desired colour is formed by the mixture and incorporation of any of the above mentioned colouring ingredients, take out a part of the mixture, sufficient to form a stick or roll of the usual size, and roll it between two smooth metallic plates, which should also be previously warmed to prevent the wax from becoming too hard. When the stick is reduced to a proper size, flatten it a little and let it cool. Proceed in the same manner with the rest of the composition; afterward hold each stick severally over a fire of charcoal, turning it quickly till the surface of the wax is completely melted, by which means the sticks will have acquired a very smooth and shining polish at the surface, which they will retain when cold again. If a softer wax is required, a small quantity of bees-wax and of linseed oil may be added to the above composition, or may be substituted in the place of the gum-mastic.

114. The art of manufacturing paper hangings.—This business, which has been usually, though improperly termed paper staining, consists principally in stamping or painting various figures in water colours on paper. The paper for this purpose is formed into long strips or rolls, by pasting the edges of several sheets together. The edges of the sheets should not lap on each other more than half an inch, and the usual length of a roll is about nine yards. These rolls are first painted plain with a large brush; the paint is composed of refined whiting with some colouring ingredient, being ground in water and tempered with a sufficient quantity of glue to prevent it from rubbing off; when a new design or figure is to be introduced, several colours are prepared, i.e. as many as are required in such design, and with these the design is painted on a sheet of paper. The paper is then laid on a smooth birch or maple board, and such parts of the paper as contain the colour that was last applied in the drawing (which is usually the white) are completely cut out, with a sharp pen-knife, and the parts thus cut out, are pasted down upon the board, immediately, in the places and positions they occupied in the design. The sheet is then removed to another board, and another colour is cut out in the same manner; thus the several colours are distributed in their proper arrangements on as many different boards. Each board is then cut away with chisels and gouges, to the depth of a fourth, or an eighth of an inch, in every part except where the pieces of paper are fixed. These boards or prints are supported by other thin pieces, which are fixed firmly on the backs of them by screws, in such manner that the grain of one, crosses that of the other, and thus prevents their warping. They have also cleats or pins attached to them which serve as handles. A trough is provided, a little larger than the prints, of one inch in depth, and having a smooth bottom, on which is laid three or four pieces of fine flannel or cassimere, each of which is at least as large as the prints. Then some of the colour with which the first part of the design was painted, is spread upon the cloth with a brush; and upon this, the print containing the corresponding parts of the figure, is pressed, (the pieces of paper having been previously scraped off;) the print being thus charged with the colour, is placed upon one end of a roll of the prepared paper, which is laid on a table for that purpose, and is pressed down hard by a lever or screw. It is then returned to the trough, and again charged with the colour, and again impressed on the paper at a proper distance above the other impression. In this manner several rolls are printed with one colour. Then the next colour in the design is applied to the paper in the same manner by another print;—a third colour by a third print and so on till the paper is completely printed with every colour in the design, each in its proper place. These prints should be washed and kept dry for future use. A variety of figures may be produced with the same print, by varying the colours.

115. To make elastic blacking for leather.—Dilute one ounce of gum-asphaltum with a pint of spirits of turpentine, in the manner described at 51;—put this into a flask, and add one ounce of gum-elastic cut into very small pieces, and half an ounce of gum-shellac previously reduced to powder. Suspend the flask unstopped over a fire of charcoal, or set it in a sand bath where it may boil gently till the quantity is reduced to a gill; then strain it through a flannel, and when nearly cold, bottle and cork it. The leather should be thoroughly blackened with some liquid blacking and waxed over slightly with bees-wax before the elastic blacking is applied. If the blacking should be too thick, it may again be diluted with spirits of turpentine. It should be warmed when applied, and the work may require several coats, and a considerable time for each to dry. Any of the above mentioned gums may also be dissolved in sulphuric ether, and thus produce a fine drying varnish, but the preparation is much more difficult as the volatile nature of the ether will not admit of much heat, whereby to facilitate the solution.

116. Sundry Experiments.—Rub together a little dry powdered alum, and acetate of lead; both will become fluid. To a saturated solution of muriate of lime, add a saturated solution of sub-carbonate of potass, (both transparent liquids,) the mixture will be nearly solid. Rub together a little pure white calomel (sublimed mercury) and pure white ammonia (being moistened;) both will become intensely black. Fill a flask nearly half full of water, and apply heat till it boils; take it from the fire and (when it has done boiling) cork it; pour cold water upon the flask, and the water inside will re-commence boiling. Fill a glass with water, and lay a piece of paper upon the top of it; place your hand upon the paper, and invert the glass; the hand may be removed and the glass may be suspended in that position by a thread, and the water will not be spilled. Expose a piece of ice to the action of (cold) muriatic gas; the ice will be instantly melted. Drop a piece of phosphuret of lime, into a glass of water; bubbles will soon rise, and on reaching the surface of the water will spontaneously explode. Apply the end of a roll of brimstone to a hot bar of iron; a part of the iron will be instantly melted, and will fall. Write with diluted sulphuric acid, on paper that has been coloured brown by a mixture of sulphate of iron, and infusion of galls; the writing will be white. Moisten the under lip, and lay upon it a piece of silver money, (not less than a twenty cent piece) with the edge of it beneath the tongue; lay a piece of zinc, of nearly an equal size, upon the tongue, and bring the edges of the pieces of metal into contact; you will instantly drop the money.