Gilding Size
An essential part of the gilding process, gilding size is the adhesive that glues the gold, silver or other metal leaf to the surface you wish to gild.
Gilding size is available in either oil-based or water-based forms, both have their advantages and uses so be sure to buy the right one for your project! As a rule of thumb any exterior gilding MUST be done using oil-based size, whereas you have the option of using water-based or oil-based sizes on interior gilding. Water-based sizes remain open near indefinitely and are useful for large projects, such as walls or ceilings.
However, there are always exceptions and Kölner have made a couple of ranges of water-based products that are suitable for use outdoors. One of these is the Kölner Rapid, a fantastic quick-drying size for lettering onto carved stone (such as monuments and cenotaphs). Another is the Instacoll System. While not a size in the traditional sense, this waterbased product, when applied correct will give a wondrously shiny gild that gives water-gilding a run for its money! It is also suitable for interior and exterior use on large projects like architectural gilding and even statuary!