I've shown this on a simple oak frame and superimposed it on a book print of a Pre-Raphaelite painting.
Gilding on the oak is reasonably straight forward. The raw oak is well sanded, stained a bit and then sealed with a thin coat of shellac. I use a long drying 12hour gold size as this will always give the brightest gild and the longest working time.
After 24 hours the gilding is given a thin coating of clear transparent shellac.
Traditionally, new gilding was given a coat to size so as to dull the sparkle of the gild. A varnish called a "gilder's ormulo" was also used to better match the colour of the gilding to the art work in the frame.
Today, the colour we see on antique picture frames is a result of all the domestic pollution and wear and tear on this thin film of size or ormulo covering the gold.
To achieve this effect, I've mixed a glaze of 10 unique indexed pigments and 4 dyes. This sounds a bit preposterous I know, for what is a simple paint effect. However, the reality turns out a bit more complex.
In mixing up this glaze, I wanted three main properties. One was a selection of earthy pigments. These are naturally occurring pigments which reflect the colours of nature so would be a good choice to represent the air-bourne dirt and grime of everyday life. On their own, however, they can dull too much the vibrancy of the gold so the next property was to brighten up the gold and the third effect is to darken and neutralise any predominant hue within the glaze - ie a black to grey glazing colour.
I've kept the mediums all waterborne, as these are easily removed and cause least damage to the gilding.