Small discs of dried paste, used for sealing letters. The mode of making them is as follows: - Take fine wheat flour, mix it with white of eggs and isinglass into a very smooth paste, and spread the same over tin plates evenly, and dry them in an oven, placing several of the plates one over the other to communicate a glossy surface to the wafers. When dry, the sheets of paste thus formed are laid up in a pile, about an inch or more in depth, and cut out into circular pieces by a hollow punch, which allows the wafers to pass up its tubular cavity and discharge themselves sideways as the cutting proceeds, which is effected with great rapidity. The variety of colours that are ordinarily communicated to wafers, is given to them in the paste, by the usual pigments in the dry powdered state, or previously dissolved in the water employed. As the ornamental substitute for sealing-wax and wafers taken from gems, seals, or Tassie's copies thereof, which was recently much in fashion, possesses some utility as a very convenient cement, we shall here add the mode of preparing it. A solution of Salisbury glue, in water previously tinged red, purple, yellow, etc, by Brazilwood, log-wood, turmeric, etc. must be prepared of a proper consistence.
The hollows of the gem, etc. must then be moistened with a little weak gum-water, in which any white or coloured opaque powder is mixed; or with the gum-water alone, and the colour in powder sifted over it; all the colour must then be wiped off the plain parts, leaving it only in the hollows. As much of the melted glue must then be poured upon the gem as can lie upon it, and be suffered to dry in a gentle heat; when it will shrink considerably, so as to become not thicker than an ordinary sheet of writing paper; it readily quits the gem, presenting a beautiful cast of it. To use it, the folded note, letter, etc. should be wetted on the part where the glue-wafer is to be applied, and the back of the wafer be placed on the wet part, when it will soon adhere, by its glutinous property, and thus form an elegant closure to the letter. It should be remarked, that this is merely the revival, and application to a different purpose, of a well-known process, formerly much used for taking casts from medals, coins, etc.; viz. by making a solution of isinglass in proof-spirits, straining it clear, and pouring it over the surface of the medal, etc.
The isinglass shrinks in drying, and will readily quit the surface of the medal; it may then either remain in its transparent state, or, by breathing upon it, a coat of leaf gold or silver may be applied to it, and thus give it the appearance of metal.
The French isinglass wafers are made in France, in the following manner. The isinglass being dissolved in water to the proper consistence, is poured out upon plates of glass provided with borders, and laid upon a level table; to prevent the glue from sticking to the plates, a little ox-gall, or other fit material should be rubbed over them. Previous to the isinglass becoming quite dry, they are to be cut through along the borders. The leaves are then removed, and cut out with hollow punches, as other wafers are. The various colours are communicated to them by pigments while in the fluid state. They are sometimes flavoured with essential oils and aromatics, as well as fruits, to give them an agreeable taste. For sealing letters, these wafers afford more security than the ordinary paste kind.