Page "Gilding" Paragraph 20

The amalgam being equally spread over the prepared surface of the metal, the mercury is then sublimed by a heat just sufficient for that purpose ; for, if it is too great, part of the gold may be driven off, or it may run together and leave some of the surface of the metal bare.

When the mercury has evaporated, which is known by the surface having entirely become of a dull yellow color, the metal must undergo other operations, by which the fine gold color is given to it.

First, the gilded surface is rubbed with a scratch brush of brass wire, until its surface is smooth.