A Counter-proof  [1] in copper-plate printing is an image that is made on a new sheet of blank paper from a freshly-printed pull from an engraved plate. The ink, which is still wet, transfers from the printed pull to the blank sheet to produce a reversed, much paler, image on the new sheet.

To make a counter-proof a freshly-printed sheet is placed, image uppermost, on a blank (un-engraved) sheet of copper on the table of the [rolling] press. A sheet of blank paper - damp as all printing-paper must be – is spread over the printed sheet then all is covered with the blankets and the assembly driven through the rollers of the press just as for printing a plate. See Printing from Copper Plates.

To counter-proof is to pass through the press a drawing in lead pencil  [2] or red chalk or made with graphite  [3]. The back of the drawing is first moistened with a sponge and the paper to receive the image is also damp.

Notes

1. There does not seem to be a modern English term that corresponds to contr’épreuve . However, the word is found in contemporary (18 ^th century) dictionaries with a definition similar to that given in this article. After defining contre-épreuve Littré says ‘.... elle sert aussi à faire connaître si la planche a besoin d'être retouchée’ ‘it is also used to check whether a plate needs to be retouched’. The engraving on copper plates produces less and less clear impressions as the plate wears. The impression can be improved by re-engraving – retouching – some lines.

2. mine de plomb graphite as in modern ‘lead’ pencils.

3. a la pierre noire Modern artists’ crayon pencils called Pierre noire are apparently made from a mixture of powdered chalk and graphite bound together with gum and a little grease.

Perhaps the distinction between mine de plomb and pierre noire , both of which seem to mean graphite in this context, is just the exact form in which the graphite was used by the artist.