The first carving I used the gray machinable wax. It carved fairly well but was too close in hardness to the base wax. This made it hard to delineate when I was carving into the base. Also the placement of this carving was on top of some nearly undisolved brown and white polyethylene (PE) spots (above the hind quarters and below the belly) which really made carving difficult. When I was melting on the build up wax some of the PE got into the build up and the result was something that would not carve but more grabbed, stretched and tore. I ended up having to dig it out and melt in more gray wax.
The second carving was with green Matt wax. It worked fairly well. The green wax carves nice although I was not patient enough to wait the requisite 24 hours for it to fully harden. It's color makes it easier to delineate from the grey base but it also was too close to the hardness of the gray wax. The placement of this carving was a bit better than the first but I still had problems with variations in the base material.
By the time I got to the third carving I knew not to place it over undisolved PE. Here I used red Wolf (TM) WAX. It carved nicely and was easiest to delineate.
I will go ahead and make a plaster mold of this so I can see how the relief carvings perform with clay.
I would like to find something that is 1) harder than the build up wax 2) I can machine easily on a wood lathe and 3) build up wax will stick to it.
The 6 1/2" salad plate prototype does have some mottling in the area to be carved but does not have any areas of undisolved PE. So, I will go ahead and make a design and try carving it. If that does note turn out to be satisfactory, I can go ahead and remelt it or try another material.