Once the object was cleaned every little crack and loss area was stabilized with a consolidant mixture of Plextol B500 water and ethanol. Plextol is an acrylic emulsion and in this mix it is dilute enough to seep into the fragile areas to protect them and prevent any further losses or flaking of the gesso and gold. Once this was completed the loss areas of ornament and uneven surfaces were built up and modeled with gesso putty, smoothed with sandpaper and a damp cloth.
The old restorations of the running flower and bead ornament at the outside of the frame were removed. Many of these were done very crudely and did not correspond to the surrounding decoration. A cast was then taken of the original area with a laboratory polysiloxan, a material commonly used by dentists.
Composition putty was made using the same ingredients that would have been used originally. Composition is made from chalk, rabbit skin glue, hide glue, rosin, glycerol and linseed oil. The mix is then kneaded like dough and then pressed into the mould to form the replacement areas. They were then carved down to fix into the frame, like a jigsaw puzzle.
All the new gesso and compo areas were then coated with an isolation layer of B-72 in toluene.B-72 is an acrylic resin which can be used as an adhesive or coating material and is commonly used in conservation due to its excellent ageing properties. Once dry the replacement areas along with the gesso fills were painted with gouache to imitate the original bole colour used on the frame. Traditional Bole is natural clay, usually an earth red or ochre yellow. Other colour varieties include grey and black. Traditional bole, as opposed to gouache, was used for its fineness which is easily burnished (polished) it provides a smooth surface for gilding and the colour will impart on the tone of the gold leaf .
Now for the good stuff- the 23 karat gold leaf. In total 6 books of gold were used, there are 25 leaves in a book. After a day of blinding gold sample surveying, the right tone and quality of gold leaf was chosen. The adhesive was painted to the surface. This mixture is the same plextol mixture that was used for consolidating the frame. The gold leaf is transferred from the book onto a suede board and then carefully cut into the desired pieces (no breathing allowed!).
Once ready the gold leaf is gently picked up with a gilder’s tip (a flat wide brush made from squirrel hair). The adhesive on the area to be gilded is reactivated by exhalation and then the gold is laid to the surface.
The frame was not completely gilded, only the damaged areas were gilded this is called in-gilding, this minimizes the restoration and provides a more sympathetic and historically authentic result.
Once this was completed the gold was burnished with a tool made from an agate stone. The in-gilded areas were then de-stressed with light steel wool and cotton as well as an abrasive material called rottenstone (not what its name suggests!).This matches the in-gilded areas with the original damaged gilded surface and unifies the whole frame.
Any areas needing a final touch of gold goodness were painted lightly with mica pigments. Mica pigments do not tarnish or discolour like commercial metallic paints,they are mixed with Plextol and are removable with acetone.