Well...

The first coat of Polycrylic resulted in a very interesting, curdled, texture but not what I want for this project. Although the can says apply a Rust-oleum topcoat after one hour; the website indicates one hour for oil and four hours for latex. 

Questions:

1) Did I not wait long enough to apply a water based topcoat?

2) Did I not spray a heavy enough coat for it to level?

3) Is it too humid?

4) Are the two products simply not compatible? 

I'll keep going with additional coats so I can test the initial concept of creating a hard barrier between the two waxes. Then, if that proves out, I'll try to resolve the curdling issue. 

Test plaster #2

Today I made a quick plaster mold of the bunnies that I carved the other day. You can see under the bellies of the red and green bunnies there was a little bit of tear out; likely caused by undercuts. I'll clean the plaster out and check. I doubt I will recast it since this just a test. Rather, I'll let it cure for a few days then try pressing some clay into it. 

Here I sprayed the other test wax model with Rustolium plastic primer. I'll let it cure for on hour then spray Minwax satin Polycrylic on top. I will apply thee coats with 1/2 hour between coats. I will then let that cure for a minimum of 24 hours before applying build up wax. My hope is the Polycrylic will provide a hard barrier between the build up wax and the base wax. 

Machinable wax

My first attempt at making machinable wax. 

Using rawkstar320's recipe and directions from Instructables, I combined paraffin and polyethylene. Then I used a wood lathe fitted with a vacuum chuck to turn the plate models (dark gray). I did the middle one first as proof of concept and made a plaster mold of it (white). The light gray plate was formed by pressing clay into the plaster. Ultimately, I plan to carve the wax and use a potters wheel to force the clay into the plaster mold. 

I tried carving the wax and found it only ok. I believe the mottling you see is due to some of the polyethylene not fully dissolving into the wax. This made for hard and soft variations in the final product. Also, none of it was as hard as the Matt green wax that I am use to carving for my jewelry models.  Is it possible they use additional ingredients such as microcrystalline or carnauba wax?

Wax build up.

I decided to try some quick carvings on the machinable wax. I built up three different waxes on the smallest prototype that I had made.

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.