The properties which render ivory so desirable a subject for the miniature painter and other artists, are the evenness and fineness of its grain, its allowing all water colours laid on its surface to be washed out with a soft wet brush, and the facility with which the artist may scrape off the colour from any particular part by means of the point of a knife or other convenient instrument, and thus heighten and add brilliancy to the lights in his painting more expeditiously and efficaciously than can be done in any other way. The objections to ivory are - its high price, the impossibility of obtaining plates exceeding very moderate dimensions, and the coarseness of grain in the larger of these; its liability, when thin, to warp by changes of the weather, and its property of turning yellow by long exposure to the light, owing to the oil which it contains. Traces made on the surface of this paper by a hard black lead pencil are much easier effaced by Indian rubber than from common drawing paper, which circumstance, together with the extremely fine lines which its hard and even surface is capable of receiving, peculiarly adapts it for the reception of the most delicate kind of pencil drawings and outlines.
The colours laid upon it have a greater brilliancy than when laid upon ivory, owing to the superior whiteness of the ground. Colours on ivory are apt to be injured by the transudation of the animal oil, a defect which the ivory paper is free from. The following is the process given by Mr. Ainslie (of Stratton ground, Westminster,) to the Society of Arts, for which he was voted the sum of thirty guineas. "Take a quarter of a pound of clean parchment cuttings, and put them into a two-quart pan, with nearly as much water as it will hold; boil the mixture gently for four or five hours, adding water from time to time, to supply the place of that driven off by evaporation; then carefully strain the liquor from the dregs through a cloth, and when cold it will form a strong jelly, which may be called size No. 1. Return the dregs of the preceding process into the pan, fill it with water, and again boil it as before, for four or five hours; then strain off the liquor, and call it size No. 2. Take three sheets of drawing paper, (outsides will answer the purpose perfectly well, and being much cheaper are therefore to be preferred,) wet them on both sides with a soft sponge dipped in water, and paste them together with the size No. 2. While they are still wet, lay them on a table, and place them on a smooth slab of writing slate, of a size somewhat smaller than the paper; turn up the edges of the paper, and paste them on the back of the slate, and then allow them to dry gradually; wet, as before, three more sheets of the same kind of paper, and paste them on the others, one at a time; cut off with a knife what projects beyond the edges of the slate, and when the whole has become perfectly dry, wrap a small piece of slate in coarse sand paper, and with this rubber make the surface of the paper quite even and smooth; [then paste on an inside sheet, which must be quite free from spots or dirt of any kind, cut off the projecting edges as before, and when dry, rub it with fine glass paper, which will produce a perfectly smooth surface.
Now take half a pint of the size No. 1, melt it with a gentle heat, and then stir into it three table spoonsful of fine plaster of Paris; when the mixture is completed, pour it out on the paper, and with a.soft wet sponge distribute it as evenly as possible over the surface; then allow the surface to dry slowly, and rub it again with fine glass paper. Lastly, take a few spoonsful of the size No. 1, and mix it with three-fourths its quantity of water; unite the two by a gentle heat, and when the mass has cooled, so as to be in a semi-gelatinous state, pour about one-third of it on the surface of the paper, and spread it evenly with the sponge; when this has dried, pour on another portion, and afterwards the remainder; when the whole has again become dry, rub it over lightly with fine glass-paper, and the process is completed; it may accordingly be cut away from the slab of slate, and is ready for use." The quantity of ingredients above mentioned is sufficient for a piece of paper 17 1/2 by 15 1/2 inches.
Plaster of Paris gives a perfectly white surface; oxide of zinc, mixed with plaster of Paris, in the proportion of four parts of the former to three of the latter, gives a tint very near resembling ivory; precipitated carbonate of barytes gives a tint intermediate between the two.