Gilding size is a special adhesive used in the process of applying gold leaf or other metallic finishes to surfaces. It is typically a mixture of water, glue, and sometimes other additives that help it adhere better. The size is applied to the surface where the gold leaf will be placed, allowing for a smooth and even application. Once the gilding size has dried to a tacky consistency, sheets of gold leaf can be carefully laid on top. The size holds the gold in place, creating a shiny and decorative finish. This technique is commonly used in art, furniture, and architectural details.