A solution of powdered rosin and denatured alcohol used to protect areas of a metal plate from the acid used in most etching processes. The varnish is made by first crumbling blocks of lump rosin with a hammer and adding it to an equal volume of denatured alcohol. It takes quite a while for all of the rosin to dissolve in the alcohol, so you have to think ahead when you first notice you’re running out of the stuff.

Stop-out is most useful when etching with aquatint, soft-ground texture or some other tonal process. One can apply the texture or aquatint to the plate and then apply stop-out as needed to places that one would like to etch more lightly, creating less dark areas on the final print. Since you can paint the stop-out on as finely as you like, you can get some very detailed highlights which would otherwise be difficult to attain. It also allows you to “erase” any mistakes you might have made in lifting up the ground in any other sort of etching before going into the acid but without having to start over again with the drawing.

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