Etching grounds are usually made in small quantities, at a single operation, by melting and stirring the solid ingredients together and allowing the mass to cool in thin sheets, which are then dissolved in oil of turpentine. The plate is coated uniformly with this varnish through which the engraver’s tool readily penetrates, laying bare the metal beneath. After the lines thus drawn have been etched by immersing the plate in acid, the varnish is washed off with oil of turpentine.
The following formulas for etching grounds have been extensively used by engravers: {724}
| I | II | III | IV | |
|---|---|---|---|---|
| Yellow wax | 50 | 30 | 110 | 40 parts |
| Syrian asphalt | 20 | 20 | 25 | 40 parts |
| Rosin | — | — | — | 20 parts |
| Amber | — | — | 20 | — parts |
| Mastic | 25 | 25 | 25 | — parts |
| Tallow | — | — | — | 2 parts |
| Bergundy pitch | — | — | — | 10 parts |
Floor Varnishes.
| I.— | Manila copal, spirit-soluble | 12 parts |
|---|---|---|
| Ruby shellac, powdered | 62 parts | |
| Venice, turpentine | 12 parts | |
| Spirit, 96 per cent | 250 parts |
The materials are dissolved cold in a covered vat with constant stirring, or better still, in a stirring machine, and filtered. For the pale shades take light ocher; for dark ones, Amberg earth, which are well ground with the varnish in a paint mill.
II.—Shellac, A C leaf, 1.2 parts; sandarac, 8 parts; Manila copal, 2 parts; rosin, 5 parts; castor or linoleic acid or wood oil acid, 1.50 parts; spirit (96 per cent), 65 parts.
French Varnish.
For red, use 1 part of eosin to 49 parts of the bleached shellac solution. For blue, use 1 part of aniline blue to 24 parts of the bleached shellac solution, as the orange shellac solution would impart a greenish cast. For green, use 1 part of aniline green (brilliant green) to 49 parts of the orange shellac solution. For yellow, use either 2 parts of extract of turmeric or 1 part of gamboge to 24 parts of the solution, or 1 part of aniline yellow to 49 parts of the solution. For golden yellow, use 2 parts of gamboge and 1 part of dragon’s blood to 47 parts of the orange shellac solution. The gamboge and dragon’s blood should be dissolved first in a little alcohol.