walling wax en · NOUN
Meanings
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(uncountable) A mixture of wax and tallow used by etchers and engravers to make a bank, or wall, round the edge of a plate, so as to form a trough for holding the acid used in etching, etc.
walling wax, to put round the plate, […]is made of bees wax, dissolved in a pipkin with horse turpentine
1811, John Hassell, Calcographia: