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Hello everyone,

Been reading these forums for some time now but never took the time to make an account even when I had doubts about certain topics.

Im beginning a small slip casting business and, also, Im new to ceramics, although Ive been reading a LOT of information and been getting things done by trial and error.

My moldmaker told me I can cast 4 or 5 pieces in one day per mold, I understand that I would need to dry it afterwards but I really think it isnt true, since when I cast a 2nd piece from the same mold it sticks and I have to leave the piece in the mold a lot of time. Is it true you cant cast this quantity of pieces?

I have other questions but I dont want to be mistaken as someone who will only get a bunch of answers and never show again.

 

Thank you all!

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The only way to cast more than once a day from a mould, is to dry it.  Drying needs air flow not heat.  Put the mould in front of a fan.

Good luck, I've never managed a successful cast more than daily in the summer, and twice weekly in the winter.  But I don't use a fan.

 

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8 hours ago, Mark C. said:

(The only way to cast more than once a day from a mould, is to dry it.  Drying needs air flow not heat.  Put the mould in front of a fan.)

This is true unless you live in the Sahara Desert 

Actually you need to have both;  air flow to carry the vaporized moisture away from the mould;  and you need thermal energy (aka heat) to convert the solid plaster hydrates to dry plaster and vaporized moisture.    The temperature does not need to be significantly  increased, but the water does need heat to become vapor.   Warm dry air is all that is required  -  just a few degrees (5-10 degrees) above room temperature is adequate. 

 

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2 hours ago, Magnolia Mud Research said:

Actually you need to have both;  air flow to carry the vaporized moisture away from the mould;  and you need thermal energy (aka heat) to convert the solid plaster hydrates to dry plaster and vaporized moisture.    The temperature does not need to be significantly  increased, but the water does need heat to become vapor.   Warm dry air is all that is required  -  just a few degrees (5-10 degrees) above room temperature is adequate. 

 

This is true.  

There are lots of considerations here as well - what kind of clay you are casting, what the viscosity/deflocculant level is, how large the mold is, how thick you're casting it, etc.  I do slip casting as my primary business and we cast 2x a day, but our molds are quite large and we cast a terra cotta that can be quite finicky.  When I cast B-mix in smaller molds, I'm sure I could do 3 or 4 casts a day.  

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I think you can get 4 casts out of a piece if the mold was totally dry to start with, and it's thick enough. Once a mold has been dried completely, it dries pretty quickly from then on because the moisture is closer to the surface. If it was never totally dried to begin with you'll have problems. A low cost way to dry them is to hang a 100 watt light bulb in a large box, and have a fan blowing in one side, with small air outlets on the other side. The bulb provides a little heat (too much heat will hurt the plaster), the fan keeps the air moving through. I prefer a small room with a dehumidifier running and a fan blowing. If you're going to be in business and making a lot of molds, I would invest in a dehumidifier and possibly create a small drying room out of wood framing and plastic sheeting.

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