Molding May

I don’t care what anybody says; THIS takes guts:

By way of explanation, this is one of the sculptures I’m working on right now, May, which I mentioned earlier. At the point you see it below, I’ve got about 16 hours’ worth of work into it and I’m preparing take an RTV (rubber mold) from it. This will allow me to make mistakes with the pate de verre, make duplicates or redo May as a bronze sometime in the future.

Of course, if something goes wrong in making the mold, there goes May. That’s the guts part.

But to put this in context…I spent most of last evening and this morning making the rubber of May. This is the finished model, in water-based clay (Hanjiki porcelain, to be exact). Since the sulfur in the clay will prevent the RTV from curing, May needs a protective coating. I spray on a thin coat of white lacquer (which lets me see where I’ve been against the grey clay), followed by a second clear lacquer coat. The lacquer fills some of the detail (very slightly), which is why the clay needs to be just a tad exaggerated. Between lacquer and final coldwork, May’s expression will be softened a bit.

Once the lacquer dries, I brush on a very VERY thin coat of two-part silicone, this one a nice brush-on thixotropic mix from Smooth-on. The lacquer also hardens the clay surface a bit, which helps keep the brush from attacking the detail.

Once the silicone is applied to the entire model, I look at the undercuts (around the hairline, for example) and any really deep crevices such as the eyes, and fill them in with pieces of an old foam cushion, cut to fit. They stick to the wet silicone, and will be covered by subsequent silicon layers, saving a LOT of time and silicone.

If the silicone could be filled with hot wax without support, I wouldn’t need to add foam. But it’s actually more of a skin than a solid mold and so needs a “mother” or rigid shell to hold it in place. If there are undercuts, deep gouges or even 90 degree angles between one surface and the next, it’ll be difficult to remove the cooled wax from the mold assembly. The more cone-shaped my silicone mold, the easier time I’ll have getting that shell off.

Each silicone layer needs to cure for 45 minutes to an hour, just until it’s tacky. When my first coat gets to that point I mix silicone for my second layer, adding some dark blue silicon pigment. This layer goes on thicker (although none of them are more than about 3/16 inch thick), over both foam and silicone. Since it’s dark blue, I can easily distinguish the next layer from the last, which saves time and prevents holes.

Since the silicone tends to goop up around the foam, I give this a bit more than an hour to cure. The next coat is just white, and goes on top of the blue, again to make it easier to see where I need to apply silicone:

I pretty much keep on doing that (and give the head an extra coat, just to ensure a smooth draft), until I have four coats on top of May. Now it’ll cure for about 24 hours, until it’s shiny and the stickiness goes away. At that point, Silicone May will get a coat of release and I’ll start troweling and shaping the rigid shell.

Another 24 hours for THAT to dry, and then I get to see if I’ve got a good mold. Getting May’s new silicone skin off will most likely trash the clay, which takes us back to the guts part.

Wish us luck!

P.S. By the way, this is part of a series of posts I’m making to describe the construction of one of my deep bas-relief portraits. If you’d like to see the whole series, click on these links:

• The inspiration for the sculpture “May”
• The constructing of May’s clay model
• The making of a silicone mold of May (this post)
• Planning May’s mold
• Making May’s mold
• Packing May’s mold
• Decanting May’s test run
• May the second (final version)
• Taking the girls for a stroll

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