View Full Version : Firing clay sculpture made on an armature
11-01-2005, 10:06 PM
This question reveals my very limited experience but I am puzzled. I want to sculpt a small figure (perhaps 12" high) using an armature. I have numerous references for making armatures, but nothing on how to complete a piece once the sculpting is finished. I understand that wire armatures cannot be left in the piece when fired. Getting a small figure off the armature seems like a difficult job, particularly with exended arms and legs (I'm thinking of doing action sports figures). I use water-based clay.
I'll appreciate tips and directions on how to proceed.
11-02-2005, 04:51 AM
Most of my experience is with oil based clay but based on my limited experience with wet clay:
If you use a conventional armature, I don't think you will be able to remove it from your figure and you will not be able to let the clay dry out fully because it will contract on the armature and crack. Your only option will be to mould the figure by one of the various methods available.
As an alternative, maybe you could use some kind of an external support system instead of an internal armature. As your clay sculpture dries out, arms and legs etc. will become self supporting and then you could fire it. Maybe someone with more experience of wet clay will confirm this (or not)
Good luck with your figure, I hope you will make WIP posts
11-02-2005, 12:53 PM
Here is an excerpt from Bruno Lucchesi's book:
"A word of caution about armatures: don't fire a sculpture that is built on an armature unless you know what you're doing! Lucchesi did in fact fire this piece with the aluminum armature still inside. The heat from the kiln simply melted the aluminum and it ran out the soles of the feet. But what you don't see is that before firing, the clay cracked as it dried on the armature. This always happens when you leave a non-yielding object inside the drying, contracting clay. So unless you're adept at repairing cracked and broken sculpture it's not advisable to fire a piece with the armature inside."
Edouard Lanteri's book speaks of using an armature of twisted copper wire and then putting a small amount of clay over the armature. At this point he twists and bends the figure to the desired action. He says that if you just used clay without the armature you'd not be able to get the pose quite as nicely as you can by manipulating the wire with clay on it.
Another advantage to using a wire armature is that you don't have to have the clay harden in order to be self-supporting. You can keep all the thin parts, like legs, and arms, moveable and workable by keeping them wet and moist. This allows for adjustments and also to be able to keep sculpting the piece and refining it over a longer period of time.
I've never used a metal armature for wet clay so I'm learning like you are. But I have sculpted a lot of figures with out an armature. On a small sculpture, (under 14"), your arms, legs, or thin areas will dry out more quickly than the rest of the sculpture. So you need to make sure your placement is exactly where you want it to be. In order for the sculpture to not fall over you can place it on a base made of clay. Or you can use just the external armature sticking in their mid-region (butt) to keep it standing. After you partially sculpt the arms, you can add them to the figure and then you must let it set for awhile to harden and become self-supporting. (But your stuck with whatever way you put it on and can't move or bend it once it's hardened to leather stage).
If you're doing an action figure that is really stout and has larger sturdy legs, I think that it would be fine without an internal armature. I'd first make a small base of clay for the legs to stand on. Then I'd model the legs and add them; if they are big enough and sturdy enough to support the body then you wouldn't have to have an external support sticking in it's behind. It would probably be a good idea to have one, though, for extra support. Then add the midregion, then, the neck, head, and arms last.
Don't forget to mist the sculpture as you see it trying to dry out too much. When done with your sculpting session, cover with a wet tee shirt and then with a plastic bag to preserve the moisture. You don't want it too wet but also not too dry. There is that perfect stage at which to sculpt with wet clay.
Hope some of this helps,:) and I too will keep an ear out for other advice on sculpting with an armature with wet clay.
11-03-2005, 03:36 PM
Roger and Tamara. . .
Thanks for the info. I have so much to learn and I guess the best way is to keep moving and learn as I go. For now, I'll put the wire armature aside and try clupting from a base with some external support.
11-03-2005, 04:56 PM
Here is another quote I found about armatures and wet clay:
Armatures can be used in fired sculptures if they are made of combustible materials or taken out before firing. See the following excerpt:
"The key to making armatures and interior supports for pottery figures, etc, is accounting for the shrinkage of the clay during hardening. For small pieces, a method I've used is to build a "skeleton" in heavy aluminum wire, then wrapping newspaper around the wire somewhat loosely, so the clay can contract without cracking. When the figure is set to leather-hard, cut the piece longitudinally to remove the armature, then score and use slip to rejoin the pieces. Alternatively, one can build the skeleton out of a light wood like pine (don't use anything that makes toxic fumes when burned) and leave it in through the firing process, when it burns out. These supports may also be removed before firing if this is practical. For larger pieces, it is best to work in sections, because having further to shrink, the piece will tear itself apart trying to contract against an unyielding internal structure."
Also, I don't know if you know of the forum site called ConceptArt.org, but they have a lot of people who sculpt action figures and fantasy figures and the like. Maybe it would be right up your alley.
Hope you keep us posted when you have a WIP to share.:wave:
11-04-2005, 07:09 PM
Is there a particular reason why you want to do the piece in water-based clay?
Frankly for all the trouble of an internal armature with water-based clay, I'd steer clear of that method (at least for now). If you really want to use an armature for a piece, try Super Sculpey or Primo (polymer clays) or oil based clay. If you really like the finished piece, you can always make a slip mold and thus cast a ceramic version for firing.
Just a thought.
11-04-2005, 10:20 PM
I'm with ceramicus on this, it may be better to sculpt in another clay and make a mold. I really wouldn't try to sculpt a figure in water based clay, a bust or a reclining figure might work but anything more dynamic just seems like more work than it's worth just to get it to stay up.
11-04-2005, 11:52 PM
For clay or porcelain to be kiln fired, armatures can be made of rolled newspaper and masking tape or bamboo skewers (the ones used for shish kabob) available in any supermarket. The skewers can be easily broken to any length, they can be tied together with cotton thread. I often used skewers with newspaper overlays.
Drape the clay loosely over the armature, since the cla iwill shirnk around 10% or so during drying and firing. If the clay is packed too firmly on the armature it is likely to develop small fisures during drying and even worse ones when it is fired. Good Luck and Enjoy!
12-21-2005, 11:47 AM
I apologize for being so slow in responsing to your suggestions. I'm beginning to understand the limitations and methods of various types of clays and their use for specific types of subjects. So far, I've been concentrating on portrait sculptures but I want to try full figures. It's looks as though I may have to change clay type or make the figures self-supporting. Jerry
12-22-2005, 09:17 PM
Hey! Don't give up on water based clay just because modern materials have appeared. Here's the deal. Clay cracks in drying because the water goes away and the clay clings to itself leaving a crack. Small cracks then become bigger cracks when you drive out the carbon by firing over 500 degrees. To avoid ever getting any cracks AND to get a clay that can self support, do this: take a white nylon rope and cut it into 3/8" sections. Pull these sections into white fuzz and then knead the fuzz into your clay. If you make your clay then add the fuzz to the dry mix. Add enough clay that when you pull apart a small ball you see a fair amount of white 'hair' sticking out. As much as you might see at the edge of the hairline on the back of your hand is right about enough. You can put a lot in but it's best not to put too little in. Now make your clay object. If it's a hollow piece you can make the clay extra thin and it will not fall apart as the hairs will hold it together. They do the exact same thing to concrete to strengthen the mix. Now, when the clay object dries the water will run along the nylon as if along capillaries and not make cracks. In fact, like tiny reinforcing steel in concrete the nylon will tie the parts of clay together and prevent cracks, even if the clay dries fast. When fired, the nylon turns into carbon dioxide and water vapor, which goes away at about 212 degrees F. The green clay will be so hard... (how hard?) that for instance there was this BIG sculpture a student left behind and after a few months we decided to put it back into the sculpture slurry bucket. Try as we might with 5 lb sledge hammers we were unable to bust it up! The figure was hollow, about 3/4" thick and over 6' tall but was self supporting during construction with no external or internal supports, just clay, grog, and nylon hairs. It had a lot of nylon and the hammers frequently bounced off the dry clay with no harm done. Amazing. We had to go to 10 lb hammers. So you can make thin walls or thin objects and the nylon will act as internal tendons to hold it up. Not when it's seriously moist, but as it dries a bit and yet still far wetter than any non-fuzzy clay can. Give it a shot. It's a cheap fix.
12-23-2005, 03:22 PM
Sounds very interesting and is worth to try out the nylon fuzz in clay. Until now I mix wet paper into the clay to strengthen it and to avoid cracks.
I tear some newspapers in stripes, put them into hot water, mix it and let all in the water until the newspaper is a grey fibre-water mixture. In summer the mix gets smelly after two or three weeks so I put a small hand full of borax into it. Then I mix 3/4 clay slip with 1/4 paper fibers well, put it onto dry plates made of gypsum, that pulls much water out. After one or two days I knead the clay and use it to sculpt. A big advantage for me is, that I can put dry and wet parts together with slip and it doesn't break when I fire it. You can fire it in any kiln, I'm very satisfied with it, because after firing you can glaze it or paint it, there's no difference to ceramics made of pure clay, as long as you don't mix too much paper into the clay.
I think, most of you know this all, the clay-paper mix is called "paperclay" and there are very many informations about it on the web.
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