This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
See also Dyes.
Take green vitriol and dissolve it in hot water. If the cement is rather fresh add 1 part of vinegar for each part of green vitriol. Best suited, however, is triple vinegar (vinegar containing 11/13 per cent of acetic acid), which is alone sufficient for well-dried places. For such surfaces that have been smoothed with a steel tool and have hardly any pores, take alcohol, 1 part, and green vitriol, 10 parts, and apply this twice until the iron has acquired a yellowish color. This mordant forms a neutral layer between cement and paint, and causes the latter to dry well.
A mordant for gold size gilding that has been thoroughly tested and found to be often preferable to the shellac-mixed article, is prepared from yolk of egg and glycerine. The yolk of an egg is twirled in a cup and up to 30 drops of glycerine are added to it. The more glycerine added, the longer the mordant will take to dry. Or else an equal portion of ordinary syrup is mixed with the yolk of egg. Same must be thinly liquid. If the mass becomes too tough it is warmed a little or thinned with a few drops of warm water. A single application is sufficient. Naturally, this style of gilding is only practicable indoors; it cannot withstand the influence of moisture.