A technical dictionary of printmaking, André Béguin.

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Etching Ground
In Abraham Bosse's treatise as corrected by Cochin in 1745 the latter points out that he knows of two different grounds. The first has "the consistency of a very greasy oil or of a transparent syrup of a reddish colour. When it is applied to the plate and is left to dry it becomes hard. Thus it may be called a hard ground." The second type of ground "when cold has more or less the consistency of pitch or black wax. When it is put onto the plate it only needs to be blackened or whitened. It does not need to dry as it will keep its sof ness and because of this it may be called a soft ground ". Each of these two grounds was used with a different mordant.
The hard ground was usually made with five ounces of greek pitch (Perrot in 1840 speaks of 120g) which can be substituted with Burgundy fatty pitch, to which was added five ounces of Tyre resin known as colophony (150g) or a common resin if the colophony was not available. These ingredients were then melted together on a low fire and in a glazed pot. Once they had melted one added four ounces of walnut oil ( 120g) or some linseed oil. The mixture was then heated for half an hour. When the ingredients began to coagulate and became like a gluey sirup it was fitered through some cloth.
Jacques Callot had told Bosse that he had his hard ground come from Italy ready made. It was a varnish used by cabinet makers which in Italy was called "vernice grosso da lignaioly". This varnish was a specialty of Venice and Florence where it could be bought in the shops of drug and spice merchants. The ingredients and preparation of this florentine varnish consisted in heating some fatty and clear linseed oil (Perrot calls for 1209) to which one then added the same amount (120g) of pulverized mastic drops. The whole was then mixed until perfectly blended and when this was accomplished the mixture was filtered through a piece of cloth into a wide-necked bottle.
The soft ground was made of five and a half ounces (somewhat more in winter) of virgin white wax (Perrot calls for 50 g), one ounce of mastic drops (30g), and half an ounce of calcified spalt (15g of Syrian asphalt). The spalt and the mastic had to be ground finely but separately. Then the wax was melted in a glazed earthenware pot. When the wax was hot one dusted into it the mastic powder while continously stirring. Next the asphalt was dusted into the mixture and the whole was stirred for another quarter of an hour. When all this was done the mixture was poured into a platter full of clean water and kneaded in the water. The kneading was done to obtain a roll about one inch in thickness from which were made little balls which were then wrapped up in pieces of taffeta cloth.
The hard ground and the soft ground were used for different purposes for a long time. Hard ground was used for results resembling line engraving while the soft ground was used for artist's engravings [* engraving]. As of the end of the 17th century only the soft ground was used and today only more or less soft grounds are in use.
The ancient recipes written up by Bosse and Cochin are as follows:
Rembrandt's ground: 30g of virgin wax, l5g of mastic drops, 25g of asphaltum or amber.
Ground discovered in a manuscript of Callot: 60g of virgin wax, 6Og of amber or Syrian asphalt, 30g of resin, 60g of mastic drops, SOg of Burgundy pitch, and 15g of turpentine oil.
Soft ground "translated from an English book" : 120g of virgin wax, 6Og of asphaltum, 3Og of amber, 30g of mastic drops (this ground is for summer use but must not be heated too much).
"An excellent ground which several Parisian engravers use at present": 30g of virgin wax, 30g of asphaltum or greek pitch, 15 g of black pitch, and 7.5 g of Burgundy pitch.
"M.T. 's ground" 75g of virgin wax, 90g of Burgundy pitch, 15g of resin, 60g of Syrian asphalt, and 15g of turpentine.
Another soft ground: 60g of virgin wax, 60g of asphalt or amber, 30g of black pitch, 15g of Burgundy pitch.
The ground used by a "very clever modern etcher": 6Og of virgin wax, 15g of black pitch, and 15g of Burgundy pitch.

All of these grounds (which have the same ingredients but in different proportions) are black ball grounds or semi-liquid ones which are laid on a hot plate. The ball grounds are applied using a dabber* while the semi-liquid ones may be laid using a brush or a roller. Since the times in which these grounds were used new recipes have been invented, such as Perrot's ball ground which was much appreciated in his times. This ground was made with 120g of virgin wax, 8g of mastic drops, 60g of Burgundy pitch, 120g of Syrian asphalt, and 4g of concentrated rubber solution. After having ground the Burgundy pitch and the mastic to the consistency of dust they were mixed and melted in a glazed earthenware container until they became liquid. Then the wax was mixed in, bit by bit, stirring with an iron spatula and reducing the heat. While carrying out the abovementioned procedure the Syrian asphalt was heated in another container to which was added the wax and resin. The rubber solution was mixed in at the very end when the other ingredients were already perfectly melted down. The mixture was finally poured into moulds. One may also distill the products dissolved in oil of turpentine. The result is heated for a quarter of an hour and then poured into hot water and worked in order to form balls.
In order to make a soft ground for crayon manner work one can use a black ball ground mixed with some vaseline, tallow, or other fatty components [ crayon manner].
The grounds or varnishes applied with a brush are more liquid than the ball ground and can be applied when cold but must be worked immediately since otherwise they will flake off when drawn upon with a point. This type of varnish is used for quick work and rebiting. The following are the ingredients for three such acid resists:

I

II

III

virgin wax

10 to 15 g

60g

90g

Syrian asphalt

30g

60g

120g

Greek pitch

30g

Burgundy pitch

60g

mastic drops

30g

oil of turpentine

250g

enough to dilute

enough to dilute

The abovementioned grounds must be prepared in a double* boiler after having been ground thoroughly.
If an etcher wishes to bite his plate a second time or several times he must use another type of acid resist. Since this resist is applied with a roller (so that it will not enter the lines) the French call it roller varnish ("vernis au rouleau"). Roller varnish has the consistency of honey in summer so that it will not run into the lines. It needs to be dried for 24 hours and is not very resistant. In ball form it is white and in liquid form it is transparent, thus allowing the etcher to see the drawing through it. This varnish must be applied on a hot plate. One can also use an ordinary ball ground dissolved in some lavender oil.
Yet another resist is used to protect the back, sides, and margins of a plate. This acid resistant varnish is used only for this purpose. The following are the ingredients for two such acid resists:

I

II

Syrian asphalt

30 g

15g

oil of turpentine

240g

240g

virgin wax

15g

4g

mastic drops

4g

copal

4g

A stoppinq out varnish is used to interrupt the biting on selected parts of the plate. Bosse used some hot olive oil to which he added some candle tallow and then boiled the mixture for an hour. However, he also had another and easier way of making stopping out varnish: mix one part wax, one part turpentine, one part olive oil, and one part lard and then boil the whole mixture. The following are some more recent recipes:

I

II

III

virgin wax

60g

30g

8g

Syrian asphalt

60g

45g

30g

mastic in drops

60g

4g

oil of turpentine

500g

240g

240g

Perrot came up with a stopping out varnish reputed to be more workable: 100g of Syrian asphalt, l0g of melted but not decomposed succin (yellow amber), 32g of virgin wax, 25g of mastic, 500g of turpentine oil, and 4g of concentrated rubber solution. Venice varnish is also used for some purposes and is made by dissolving venitian turpentine in turpentine oil. It is much the same as the varnish used in painting.
Alcohol varnish is used for retouching plates since it dries rapidly but its drawback is that it tends to flake.
All of the grounds and acid resists mentioned in this article are also commercially made and are sold ready for use.

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