Court Plaster
This plaster is a kind of varnished silk, and its manufacture is very easy. Bruise a sufficient quantity of Isinglass, and let it soak in a little warm water for twenty-four hours. Expose it to heat over the fire until the greater part of the water is dissipated and supply its place by proof Spirits of Wine, which will combine with the Isinglass. Strain the whole through a piece of open linen, taking care that the consistency of the mixture shall be such that when cool it may form a trembling jelly. Extend a piece of black or flesh-colored silk on a wooden frame, and fix it in that position by means of tacks or twine. Then apply the Isinglass, after it has been rendered liquid by a gentle heat, to the silk with a brush of fine hair (badger’s is the best). As soon as this coating is dried, which will not be long, apply a second, and afterward, if the article is to be very superior, a third. When the whole is dry, cover it with two or three coatings of the Balsam of Peru. This is the genuine court plaster. It is pliable and never breaks, which is far from being the case with spurious articles sold under the same name.
Source: One Thousand Secrets of Wise and Rich Men Revealed, C. A. Bogardus