Questions on a DIY Slumping Mold

Glass Working
#1

Hey Glassies. Need some expert advice. I just took the slip molding class and I’d like to build a glass slumping mold out of slip. I’ve made molds before so I’m good there but I don’t know anything about clay. Should I be using a high fire or low fire clay for a glass slumping mold?

#2

I would be inclined to use the mid-fire (Cone 6) stuff. While low-fire is fired to Cone 04, I personally feel like you’d be surer of a stoneware clay never starting to melt on you.

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#3

@meanbaby

I would personally use cone 6 but it probably doesn’t matter as long as you remember what you used.

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#4

Just an FYI mid fire slip is rare for slip casting. Porcelain slip is the only mid fire slip I recall using and it was for dolls and specialty items. If you go to a ceramic shop it’s all low fire.

Slumping and draping firing temps are way lower than what low fire slip is fired at. When I make glass molds I use low fire.

I hope you have a great weekend, I will be out of the loop for a bit.

Anita Willis

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#5

We buy a Cone 6 slip from Trinity. I’m assuming it’s stoneware, because the Cone 6 porcelain is really weird if you’re making pots with it.

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#6

I am thinking DMS took up cone 6 for 2 reasons.

  1. they had not a clue what the norm was for general slip cast

  2. they could use cone 6 glaze since that what DMS has. The items I’ve seen done look awesome.

Low fire glaze come on smaller size and are cheaper.

I bought some cone 6 slip to give it a try. Please fire the big plate on top the big kin. It needs to be fired in a flat surface or it will warp or crack.

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#7

I already had my own glazes which were cone 6 so I do cone 6 slip but it is a pain to find what I need when most of slip casting is low fire. And yes it is more expensive. For slump molds it’s probably not going to matter much either way. I know of another Makerspace that was probably going to go with low fire as their standard last I checked.

#8

It fits into our normal firings, and doesn’t require slip-casters to have to put info on every single piece that gets fired. OTOH, the whole “having both” has me pausing and getting info before I’m willing to fire a glazed slip piece at Cone 6. Melted bits are no fun.

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#9

Thanks for all the feedback. In the end Trinity Ceramics told me to go low fire for glass so I bought both low fire and a cone 6 and will experiment. Will let you know what works best!

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#10

And, since you won’t be glazing a slump mold, you’ll only be sending through the bisque firing, which is a good temp for both bisque and Cone 6. Low fire doesn’t go any higher, so you’re golden.

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