This is intended to supplement, with my experience, other excellent articles which have already been written on this subject. In particular, I recommend "Getting Started with Sculpting" by Rick Barrows and "Sculpting and Figures" by Adrian Bruce. As with most of my articles, this is a work in progress. I consider myself to be in the process of learning. As I gain more experience, some of this information will be amended and revised. (revised 02/12/99)
At this time, I no longer see Polymer Clay as a "permanent" and "final" material-- Instead, I see it as the starting point--a prototyping/mastering material in a process which results in lighter and more durable resin castings. As such, it's a great material because it lets you work on sculptures at your leisure and in stages. It is suitable as a permanent material for small pieces, but that's not the way I usually use it.
Because of this, I no longer see the issue of material strength in quite the same light. I expect pieces to suffer some damage as they're demolded, and in some cases I've only baked the surface of the clay before making molds. However, if you use these clays for your finished piece, this issue should be of great importance to you.
| Polymer clays
fire at relatively low temperatures, from 200 - 275 degrees Fahrenheit.
I currently bake them at 245 F in a gas oven (where the heat is more consistent
than a toaster oven), and don't keep track of the time very carefully. In
my experience, when cooked at the manufacturers' recommended temperatures
(275 F), the clays often change color, smoke, and sometimes blister. Other
methods have been suggested, including boiling (Sylvia Szilagyi) and localized
heating with a bunsen burner (Tung Nguyen). I routinely use a heat gun to
do shallow spot baking for pieces that I need to handle without worrying
about damaging the finish.
IMPORTANT SAFETY NOTE: Baking in an oven that you use for cooking foods is not recommended because the chemicals can condense on the walls and contaminate foods when the oven is reheated. This may cause health problems. It's unclear whether it's more dangerous to do this than to sacrifice cooking healthy foods for a diet of fast foods which don't require you to use your oven.
As of this revision, I have used Sculpey, Super Sculpey, Sculpey III, Promat, Premo and Fimo. Each has unique characteristics, and a good comparison can be found at Prairie Craft's website. It seems that there is no "perfect" clay-- a desirable property may be a liability when used in a different situation.
It is possible to blend clays to give you a better blend of characteristics for a particular project. For example, I currently prefer Super Sculpey for its sculpting characteristics, but have a difficult time seeing detail because it's a translucent material. I have started adding Sculpey III to this mix (when I'm not too lazy).
Prefiring: This is the softest of the polymer clays, and therefore very easy to work with when forming and smoothing large areas. This is a liability when sculpting details, however. To sculpt details, the medium should have some firmness so that sculpted details don't move around as you're trying to add new ones.
Postfiring: This stuff is way too soft for my tastes. It crumbles too easily, and I've pulled up chunks of it when lifting objects that I'd placed on top of a fired & painted Sculpey base.
Prefiring: I like the way this stuff handles. It has just enough firmness for sculpting details, and isn't too bad for doing large areas. Unfortunately, the pink translucent material is really hard to see when sculpting details and many of the finish flaws are not apparent until after the piece has been fired and primed.
Postfiring: A very hard, sandable surface. You can use steel wool and plastic polishers to put an amazingly smooth finish on this stuff. The main problem with this material is that it is brittle. Thin parts will snap with just the slightest bit of pressure. I feel that this material is perfect for prototyping a master sculpture which will later be cast in resin.
Prefiring: This is very similar to Super Sculpey, but I think it may be slightly softer. I have heard that it's just a colored version of SS, but it seems slightly different to me, and I prefer SS.
Postfiring: Like Super Sculpey, but I believe that the parts are slightly more fragile. I'll confess that it's a totally subjective assessment since I don't have scientific instruments to test this stuff. Maybe I'm just being influenced by SIII's more jovial colors?
Note: this material is no longer being produced and has been replaced by Premo. (I didn't bother revising the text, since it's so quaint.)
Prefiring: I haven't worked with this material for very long, but I like its feel for sculpting details. It is substantially firmer than Super Sculpey, so the pre-sculpting kneading ritual is far more strenuous. As expected, it is much harder to work smooth surfaces into large areas. Another undesirable characteristic is the dryness of the sample I've been using. When sculpting, bending will often produce a tear rather than stretching. I think this can be avoided by strenuous kneading, as your skin oils mix to improve the pliability of this material.
Postfiring: I've test fired a few pieces, and the material is very tough and rubbery. The surface isn't as hard as Super Sculpey, and pieces have some "give" when stressed. Unfortunately, this means that the material is not as sandable as Super Sculpey, so you'd be wise to do a pretty good job on the finish before you fire it.
This material replaces Promat, which had problems with "thermal stability." This means that the stuff cracked as is expanded & contracted, especially for big sculptures (and I'll testify to that fact.) It's really a shame since I learned to like its sculpting characteristics.
Prefiring: A stiff-assed clay which is hell on your hands to condition. The material is somewhat rubbery; even more so than the Promat formula. This can make it frustrating to work with, since you push and the material compresses instead of just taking the indentation like an obedient piece of clay. It's not as big a problem when you're doing fine details. Maybe I'm being unduly harsh because it's made my hands suffer so much?
Postfiring: This is the strongest of Polyform's clays-- it's resilient, so you can form thin pieces which bend instead of snapping off. It sands well too.
Made by Eberhard Faber. I haven't used this in quite a while, but it's very similar to Promat in almost every respect (but more so)-- the horrendous kneading, the dryness, the durability characteristics after firing. In thin sections, this stuff actually tears rather than breaks!
| Selecting the
best tool for sculpting depends on the type of sculpting you're doing. For
detail sculpting I mainly use "ol' Bessie"-- She's a steel spear tip on
one end (for carving), and a blunt nub on the other (for smoothing and pressing).
Other specialized tools occasionally come into play, like X-acto blades,
screwdrivers, pins, brass tubing, or an occasional custom-made epoxy putty
stamp. For larger areas, I use Fimo's plastic set which comes with a variety
I prefer to use one primary tool, since you can concentrate better if you don't have to keep swapping (and looking for) tools. Also, I prefer steel tools since I can use them with epoxy putty (which sticks to everything), and sand them down to clean them.
To help soften Promat and Fimo, I've used small amounts of 3-in-1 oil to lubricate the surface. This makes it soft and tacky, so fingerprints are a big problem. It does seem to fix the dryness problem though.
From a mechanical point of view, if you're aspiring to be a 3-D photocopier, the single most important thing is to have good reference photos or the actual object in front of you. The best reference photos are mug shots-- front and side profiles. From there, you interpret the shadows and highlights to determine the 3-dimensionality of the surfaces. Ideally, your front and side renditions will match up into a cohesive whole, meaning you've interpreted the photos well. It really helps to have a "highly mobile" sculpture so you can quickly manipulate it to see it from different angles, and access it to make corrections. Once you mount a sculpture on a base, or the sculpture gets large, you lose a lot of that "mobility", and the process bogs down.
It's best to start working on general shapes and proportions first, before working on any details. You will need to rough in some basic details as "landmarks". These give you reference points for positioning other rough details. Don't grow too fond of anything you've sculpted by succumbing to the temptation to work on details too early. You may have to obliterate them later, or substantially modify their position. As you work the planes and surfaces, the landmark positions become more certain, and you can safely begin to detail them.
Throughout the process, much depends on the training of your critical eye. This is crucial and probably impossible to teach-- it's the ability to tell when something is wrong, and when something is right. It's also the ability to localize the problem area and work on it, instead of another area that's really okay. If you sculpt something, and say, "hmmm, something's not quite right...", then have hope! Your critical eye is working. All you need to do is get it to tell you what's wrong.
A curious thing happens to me as I work on something for a long and continuous stretch of time: the critical eye gets fatigued. It seems like the visual image of what I'm working on overpowers my ability to look objectively and critically at the piece. The only thing that fixes it is walking away from the project for a while and coming back later for a fresh look. I've done a few pieces that I wished I'd waited a few days before firing them. After the fact, the flaws seemed so obvious, and would have been so easy to correct if I hadn't already fired the pieces!
Don't get discouraged, and be patient. You can only get better by doing! If it doesn't look right--it will eventually--but only if you're willing to put in the time and effort.
Jimbob-- 04/05/97, 02/12/99