EVA'S HEAD

Last modified: Saturday, January 6, 2001 6:20 PM

 

10/30/99- So you've sculpted the head in Super Sculpey (or whatever polymer clay you choose to use), think you've got the symmetry right, and got it reasonably smoothed down before you bake it. Then you notice a few things that are off, fix them, give it another smoothing session. After all the hours you've invested, you might think, "Well, that's done..." Uh uh.

Unfortunately, the camera refused to focus on the Super Sculpey master at top, but I swear that it looks fairly okay, except for the grafted-on patchwork at the right ear. Generally, with Super Sculpey you just can't tell very easily, which is why it's a good idea to mix Super Sculpey with another more opaque polymer clay. I'd do it, except I keep forgetting.

Picture #2 is a raw casting. If the picture were larger, you'd be better able to see the numerous flaws (and the pic would take a lot longer to download). Of course, there are casting flaws, like little tiny bubbles-- I didn't vacuum the silicone mold because I made a thin one-piece skin mold with several pours. However, the big problem is that there's a lot of off-symmetry and a horribly poor finish. The top down lighting and magnification show this clearly-- it's barely noticible to the naked eye. Notice that these flaws are revealed because resin is a more opaque material than Super Sculpey.

Picture #3 is a partially refinished casting: 4 hour's worth of additional work, so far. It still has some flaws (like the asymetrical eyes, chin & cheeks), but I've added some patchwork to help the lip and nose symmetry. Most of the refinishing was done to take care of smoothness problems, but there were a large number of tooling marks and joins where clay was added on. It's very difficult to blend clay add-ons to stand up to magnification. Usually, they need further post-bake finishing.

The left picture shows a very large bubble in the ear. This is where air got trapped during production of the mold. During casting, it fills with resin, and in some cases produces a perfectly spherical bubble which is easy to remove. This one is firmly planted and needs to be grinded out.

The right picture shows how blind you can be when sculpting clay: It isn't nearly as obvious on the clay master. The added-on clay seam is poorly blended and clearly visible. It's humbling to see the level of surface imperfection when viewing at extreme magnification. You can smooth out minor surface imperfections of the clay's finish before you mold it by giving it a good dousing of a spray sealer (which I didn't do). It would tend to obscure detail, but some detail is better left unseen.

One of the frustrating things about finishing resin is that there's a good possibility that you'll sand down into tiny pinholes. The resin I've used isn't horribly old, but it did happen in one small area. It's only noticible through extreme magnification, and even a thin paint coat would fill them easily enough. If I were to venture a wild-assed guess though, this would seem to be the reason why professional sculptors in mass-market toy production (or folks that strive for perfection) often make at least two castings: The first one in wax, so that the finish can be smoothed perfectly, and the casting of that for production. Fortunately, I'm not so afflicted (with perfection): I've tried working with wax once and got the results one would expect from someone who had tried working with wax once.

In case you were curious about the "skin mold": This is an unboxed mold, similar to a latex mold. The pattern gets a thin impression coating of low-viscosity, low shore-A value (with good tear strength) silicone. Once cured, a thickened mix of silicone is painted over that. Because the wall is thicker than a latex mold (unless you use a zillion layers), it doesn't need a mother mold and the casting can sometimes be demolded without slitting (so you don't get any mold lines). Of course, it's a brutal process, somewhat akin to giving birth to a pumpkin (I imagine). This uses much less silicone than a traditional box mold though, and that's a consideration if you're not doing it for production, and don't care about mold longevity. There are other drawbacks though-- there are much more likely to be large entrained air bubbles in the thickened silicone, which means a weaker mold. Also, the thin impression layer may break through to one of these larger pockets. Although the impression coat is likely to be bubble free, the forces of nature work against you: the silicone flows down, instead of around, sometimes leaving things like nostrils and earholes with tiny bubbles of trapped air (see pic above).

Skin molds are good for making slush castings: Because they're thin, you can squish them with the small amount of resin inside, ensuring that the resin gets into all the detail. At a certain point in the process though, you do have to resort to the rotation coating, to help distribute the ever-thickening resin. Unfortunately, it seems to have an exponential cure curve, so you're likely to get a thick wall somewhere.

There are a few reasons for making a hollow cast head (versus a solid head joined to the neckpin): The vintage design permits forward/backwards and rotation of the neckpin within the body socket, but they're always in tandem. The head/neck rotation allows an additional axis of independent movement which lets your figure assume "cocked-head" poses. This is an important consideration for giving your figures poses with "character". (Of course, the trade-off is the additional seam line-- that's why most of my gals wear chokers.) The other reason is that the heads are easier to swap out.

Titankhamun? (yuk, yuk)

 


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