In this class we worked with water based clay. Philippe recommended oil based clay or silicone wax for my work. Wax is an excellent material as you can use the lost wax method of casting.

Oil based clay is more conducive to the long modeling process involved with French furniture. The clay must almost always be modeled directly on the case piece to ensure a good fit. The shrinkage of the bronze must also be taken into account. That can range from anywhere between 1.4% to 5%. You have to contact your local foundry to find out specifics. As the bronze cools it contracts and if this isn't taken into account your final bronze will not fit the case piece. It can still be mounted (a complex process that deserves its own post) but it won't fit as well.