Casting a Clay Model
in the previous tutorials i have repeatedly spoken about, how important it is to have good references… also, i spoke about using clay models to guide the carving… however, a clay model is soft, and when repeatedly measured on it, it looses shapes, so a way out of this is to cast it in plaster. this is what i want show here in this tutorial. of course, this casting of the clay model is not only limited to the use as a firm model for carving, but one can use it as a finished work, and paint it in faux bronze, or faux marble or whatever one likes to …
i am going to make the mould in plaster, and after that cast in plaster too. doing the mould in plaster, requires that the clay model is soft. since my model is made from plastilin, it will stay soft forever. if you use a model from waterbased clay, you need take care that the model stays soft enough while creating the mould, otherwise, it might be impossible to remove the clay from the mould.
also, the method i am using is not for the faint heart, since the clay model gets destroyed in the process, and usually the mould is destroyed after the first cast too. so, it means, one gets one good cast or none at all… and, i should say, i am pretty new at doing moulds, but i like to share what i learned so far,,,so, if you see things i could improve, please let me know
ok, let´s start ….
Fiebig and Yundt Woodcarving 
Doug Duffield
May 09, 2010 @ 17:27:59
Doris, are you an engineer as your ‘day’ job? 😉 I worked for about 20 years in the plastic injection field and your approach to creating a plaster mold is very sound. As you say, the clay model will be destroyed as the undercuts around the ears, nose and other areas will not release from the plaster. Your use of clay ‘keys’ to register the mold parts is very ingenious. I look forward to the rest of the tutorial!
Good luck with the rest of the project!
dorisfiebig
May 10, 2010 @ 15:51:38
hello doug,,,no not engineer, but mathematician, and so, solving problems is my profession …. i read lots in internet about making moulds, and, i collected the info´s i thought might work for me, and so i tried… yes, i am excited too, i hope he comes out nicely in the end…
Tamara
May 11, 2010 @ 22:18:34
I’m so happy for you Doris! To have the front come off that well means that you could almost not have to chip it off when making the plaster cast. With all the shells that you made for the back, it too may come off without chipping away. Then you could make a couple of casts instead of just one. Practice makes perfect and your getting there. 🙂 I feel your excitement about the cast and look forward to seeing it.
dorisfiebig
May 12, 2010 @ 20:13:25
yes, Tamara, i was really surprised how well the front came off. we will see, what happens, if more than one cast great, but i am really happy if i succeed with just a single one. one the first cast i did, the face shell came off easily after casting, except that over the eyes, and in the nose holes were left plaster from the shell, which i removed carefully. i would think such happens always when casting plaster in plaster mold,,, it adds to the excitement, thinking of more than one cast possible … thank you for your nice comment, tamara
Tamara
May 19, 2010 @ 17:35:52
Those are all fixable things which is very good. Just by scratching the surface of the damaged area and applying water to keep it moist, one can add plaster to stick to it and then sculpt. With just a little tweaking of your casting process, I think that you can have a workable mold to try several castings. Benefit of that is very often the first pour doesn’t turn out well. I’m happy that this one can be reworked and you’ll have a finished sculpture that looks great in the end! Thanks for all the pics to see your progress.
dorisfiebig
May 19, 2010 @ 20:44:50
hi Tamara, yes you are right, it was all fixable. i spent the weekend on fixing, you mentioned earlier to me that it is necessary to wet the cast when i want apply new plaster,,, so i did, and it worked out fine. i even remodeled the missing ear, directly in plaster … it is amazing, how one can work with plaster, it was a great experience… now the cast is drying, it still is cold to the touch, which means it still is wet. as soon as it is dry i will share pictures of the final….
yes, i see this also as a learning pprocess. many things went well, and the ones which did not, i can try to tweak to get better result next time… now, i believe, the vaseline was not so good as a seperator as the dish-washing-soap i used for “autumn begins” was… anyway, this casting, is an exciting work, and i feel really happy now looking at the repaired cast… thank you for following my journey.
Ralph Giarnella MD
Jun 16, 2010 @ 12:58:50
I liked your tutorial on making a casting. A dozen or so years ago before I became interested in wood carving I tried my hand at sculpting in clay. The method I learned was similar to what you demonstrated with one difference.
Instead of making the master mold out of plaster I used liquid latex to cover the clay model. It was somewhat tedious in that the latex had to be brushed on in layers and took several days to get a robust thickness. If the original has many contours one could use the same method of sections simply by using keys similar to what you demonstrated with the plaster.
Once the latex cured I made a supporting cast over the latex using the method you demonstrated with keys so that the supporting cast could be removed in sections.
The next step is to dis assemble the supporting cast and the latex from the original.
The result is a latex master mold which will not be destroyed and could be used multiple times.
To cast a plaster model simply assemble the latex master in the supporting cast and pour in the plaster in the manner you demonstrated. Once the plaster is cured disassemble the supporting cast and remove the latex.
This method is takes more time and is more expensive (latex is not cheap) but is useful if an individual would like to make muptiple casts of an original.
Doc
Ralph Giarnella MD
Southington Ct USA
dorisfiebig
Jun 16, 2010 @ 13:53:36
hello ralph, thank you so much for the indepth description on how to make a latex mold. what a wonderful addition to the tutorial. it is very clear, and very useful. indeed, often i think, one would like to make a few more casts, not just one. also, since one could better try out things. thank you again, for your comment and for your sharing of knowledge. very appreciated.
Ronald Bushnell
Dec 14, 2011 @ 09:15:32
Thank you for the information. I am currently making a model from a model of soft Modeling Clay. I choose to work out the form and details in the clay, without taking it all the way to fine detail; such as toes with no toenails. The actual model will be carved in Yellow Cedar allowing great detailing. This model will also be a finished piece in itself. Any minor correction in the first “carving,” will be done with epoxy sculpt and or oil color as this Egyptian motif will be a three dimensional canvas. The perfected “hard copy,” will then have the potential for a mold for copies; as well be the master for the final carving done in perfect wood.
dorisfiebig
Dec 14, 2011 @ 22:13:58
hello ronald, i am glad to hear the information i provided is useful. afterall, that is the reason for sharing, the hope someone will be in the situation to need the information, and finds it here, and can go on 🙂 … also, it is great to hear your approach, i like how you planned to work up slowly to a finished piece, by first concentrating on basic shapes (toes, but no toenails), and developping it further to finally reach a point that might be worth for many copies… yes, i too tried to work the models, i use for carving, further into finished models. even though, i have then two finished pieces of the same topic, they are different, much different in character. i like that… thank you, for sharing your approach, and letting me know my article was useful for you.