The first stage in making a gilded frame (after it has been joined, had the corners filled, and the whole frame has been sanded), is to apply a size coat of rabbit skin glue. This primes the barewood surface and will help to create a strong bond between the gesso layers and the wood substrate. If the frame is not given a size coat the glue in the gesso is absorbed into the wood and the bond will be very weak. The glue granules are mixed 1:8 with water and left for 24 hours to soak. The glue is then heated in a double boiler and brushed on very warm, but is not heated too much as overheating the glue causes the adhesive to break down, and become useless. The frame is left for a day before the next stage, which is the gesso. Sometimes strips of fine silk are put over the mitres, this interlagio helps to reduce the inevitable cracking that occurs at the mitres, as the wood shrinks, expands, and moves during variations in the surrounding atmosphere.
