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Jaay

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Jaay    0

I have just finished a sculpture out of what the package describes as "natural clay". The brand name is "craft smart" out of Texas. The piece has dried in air for over a week, and is what I would call "green" (if I remember correctly from high school art). I want to create a silicone mold of the original to create a series of reproductions, but I'm worried about the original surviving the process,as there are some thin sections. Would low temp firing, say in my oven, strengthen the clay, or am I at risk of blowing this up?

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Chilly    331

What are you going to cast in your silicone mould?

Traditionally, moulds to cast clay are made from plaster.  If you want to make a plaster mould, you should use wet, solid (not hollow) clay as your model.

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Jaay    0

I'm actually casting a mold of the sculpture so that I can make copies of the original. I'm just wanting to know if baking my sculpture (but only to around 500 degrees Fahrenheit) will strengthen the clay, or if it would be a wasted step. I appreciate anyone spending time responding to what is really not a "ceramic" question.  I may just opt to seal the sculpture with acrylic as is, and hope for the best.

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If you're looking to make a master to make a mould from, then yes, sealing your current sculpture with acrylic is likely your best bet if it's already dried. Baking it in the oven won't turn clay into ceramic, or make it more durable at all.  You need hotter temps than your oven can generate.

Mould masters can be made out of plaster, as Ann mentioned, but you can also use wet clay, and in fact that may have been easier to release from the mould.  At this point, I'm guessing that's more of a "for next time" piece of information. You can also use things like plasticine, so that there's some give if you have undercuts.

 

 

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Your mold will be more successful if you make it using the wet clay.  Since your piece is dry, I recommend spraying it with non stick spray or lightly brush on some dawn dish soap to allow it to release better. 

 

What I would do: I would make a mother mold out of agar agar (vey concentrated ) I would pour it over the sculpted piece and stop when 1/2 covered ... wait 10 seconds and then continue to pour so it delaminates easily in the middle. You can use an old plastic ice cream container or something to place item in and to pour. 

Then I would use agar agar mother mold (will feel like rubber) and put small hole inside top to pour in plaster. Use thinner plaster mixture at first to get in small crevices before pouring it the rest of the way. -- now you have a plaster sculpture to re use for mold making and to make your silicone mold with. The clay sculpture that you used with agar agar will be saved. (But I think silicone would be just as flexible ?)

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Jaay    0

You've been so incredibly helpful. The "won't make your clay more durable" was the nugget I've been searching for.  I'm very reluctant to take this to the next stage, as I am very proud of this piece, but the whole intent of the clay was to make a mold so I could cast many versions of this to create other variations. I would download a photo, but apparently it's too "bit rich" for this platform. Can't thank you enough for your advice and expertise.

I will be using silicone to make the mold, and plan on using acrylic as a sealer, then a universal mold release spray (essentially vegetable oil).

Wish me luck.

 

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oldlady    1,323

jaay, if you use paint to reduce the size of your photo, it is easy.  at least easy enough for my ancient brain to process. right click the mouse, open with, choose paint, go to home, then resize and choose pixels.  if you enter 600 for the horizontal, it will automatically make the whole picture the right size, hit save and then it will work for email or to post here.   i think i put this in the correct order.   edited because i messed up the sequence.

Edited by oldlady

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One more thing I don't think was mentioned.... bone dry clay is probably the most fragile state of clay. Putting it in an oven for 500* will make it more fragile. 

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