This is a mid-19th century Serpentine Toiletry Casket with Boulle style marquetry. The box has engraved brass and red turtleshell inlay on what looks like a mother-of-pearl background. However as you can see, the surface has many cracks that are typical of early cellulose nitrate plastic.
First I compared this plastic mother-of-pearl and real mother-of-pearl. Here you can clearly see the difference between the two materials, with the real mother-of-pearl showing characteristic iridescent interference colours (generated by thin layers of the mineral aragonite, a form of calcium carbonate.)
Left: genuine mother-of-pearl; right: synthetic mother-of-pearl
There were a number of areas of missing decoration. The first task was to adhere coloured silk and Japanese tissue paper to the missing areas inside of the box using wheat starch paste.
Above: the paper and cloth linings before treatment; below: the same after treatment
There were splits in the wood that I re-glued with fish glue, then held between clamps to dry. Fish glue is a little less strong than animal glue, which is normally used on furniture, but because this is just a small box I chose fish glue because it is easier to control and has a longer open time.
I made up mother-of-pearl patches using a modern synthetic substitute material. The lost areas of turtleshell were replaced using a transparent epoxy resin and pigments. I used Aralidtie 2020 for its excellent working properties. I made this mini shimbari frame to apply a small amount of pressure (the amount of a finger) on the fills.
Here on the left, you can see that a piece of veneer is missing. On the right, I filled this loss with boxwood and colored it with acrylic paints and coated it with shellac. I also applied shellac over the entire ebonized veneer to compensate for the missing finish.
A very small area of brass was also replaced. The treatment was completed after some final colour matching using acrylic paint.