We all know that all that glitters is not necessarily gold, but with sales pitches that use the term gold leaf indiscriminately it can be difficult to make informed choices when choosing gilded picture frames. The easiest way to discern a difference is cost: mouldings at a few dollars per foot are not genuine gold. That said, however, expensive mouldings are not necessarily real gold leaf either. For the purposes of this essay I will use gold for genuine leaf and GML for imitation leaf.
Goldbeaters produce a range of gold leaf from 10 karat up to 24 karat. Genuine gold is alloyed with either copper or silver to form a gold leaf that ranges from red (with copper) to pale colours (with silver).It is packaged in loose form for controlled environment leafing (i.e. no wind), and transfer or patent gold that is adhered to tissue paper for leafing outside or in large spaces where one can expect to find draughts. There are different grades of leaf single weight, double and triple weight, plus glass leaf without pinholes for gilding on glass or where opaqueness is essential. International standards govern the production of both genuine and imitation leaf.
Leaf is cut into 3.25-inch or 85-mm squares and packaged 25 to a book and 20 books to a pack, for a total of 500 leaves per pack. The weight of gold is measured in grams per 1,000 leaves. With this measurement I know that 18-karat lemon gold contains 16 grams per 1,000 leaves from one goldbeater and another lemon gold from a different goldbeater is 21.5 karat and 19 grams per 1,000 and I can make a choice knowing that the latter is a heavier weight and therefore better for burnishing and will result in a brighter look.
The above, rather technical, description of gold leaf does not allude to that quality of gold that has entranced mankind since time immemorial: its ability to trap and reflect light. I remain amazed and gratified even after 35 years of gilding, at how a gilded frame can pick up ambient light and reflect it back in a darkened room. It is this quality of light and reflection that distinguishes gold leaf from GML.
GML is an alloy of copper and zinc and is produced in four colours numbered 1, 2, 2-1/2, and 3 with 1 being most red (more copper) and 3 being most yellow (more zinc). It is cut into 5 inch squares. If gold leaf is the thickness of newsprint, then GML is the thickness of matboard. Whereas gold leaf can be water gilded and burnished, GML can only be oil gilded and cannot be burnished. It must be sealed to prevent discoloration due to corrosion. Since GML is brass, it will never have the depth or reflectiveness of genuine gold.
One of the distinguishing features of genuine gold gilding is the overlapping of the layers of leaf. Some mouldings laid with GML are cross striped with white shellac to give the appearance of overlaps, a close look will reveal the stripes of shellac.
For more information visit the FACTS (Fine Art Care and Treatment Standards) website at www.artfacts.org.