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Porcelain slip casting recipe

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I think I have two in an my old clay mixing book-Its been 35 years since I have used these-not sure on thin strength .These are all cone 8-10

All old school stuff here

 

Mark

casting porcelian

spar 25

epk 40

flint 25

ball clay 10

+sodium silicate 1/4 of 1% or 1/2 tsp

strain 6-8 times-60-80 mesh screen

 

Pats casting porc slip

EPK 2.5 lbs

ball clay 2.5 lbs

silica 2.5lbs

spar 2.5 lbs

 

HSU casting porc slip

3 gal.

EPK 25 3405

Ball clay #4 25 3405

Feldspar 25 3405

Silica 25 3405

Sodium Silicate 34

Soda Ash 34

12 lbs.

Add deflocculants to water 1st

4 lbs H20 for 10 lbs. clay

 

when I had a slip casting business for 12 years we used darvon instead of sodium silicate to deflocculate it works better-we cast 40,000+ candle lamps

and gave up on soda ash as it hard on the plaster molds over time

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Hello ... I recently mixed a fresh batch of porcelain slip and mixed in some older slip that I'd had a some months.

It mixed smoothly, but now, after a few days, the water is on top and all thr solids are on thr bottom of the bucket. When I try to use my drill mixer, it's clumpy and hard to do. 

How do I fix this? I thought about scooping the mix out by hand and sieving it into another bucket. 

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7 minutes ago, mishelart68 said:

Hello ... I recently mixed a fresh batch of porcelain slip and mixed in some older slip that I'd had a some months.

It mixed smoothly, but now, after a few days, the water is on top and all thr solids are on thr bottom of the bucket. When I try to use my drill mixer, it's clumpy and hard to do. 

How do I fix this? I thought about scooping the mix out by hand and sieving it into another bucket. 

What are you using as a deflocculant?

I had issues with hardpanning when I used sodium Silicate, but when I changed to darvan 7, no issues.

I use a large drill with a big ole blunger on it, it has a "hands free" trigger setting and if it's been a while I just hook the cord under the bucket and let it mix itself for 10-15 minutes.  After that it's usually smooth as silk

 

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2 hours ago, mishelart68 said:

Okay ... that must be it. I used sodium silicate in my mix. 

How do I correct the problem since I've already used sodium silicate? 

I believe you need to mix it every few days to keep it from doing that.

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I'd say it's the amount of sodium silicate, not necessarily the sodium silicate itself that's the problem. I've mixed batches of casting slip with SS and never had problems. If it's separating out, then it's probably been overly-deflocculated, or has too much water. You could try adding dry material.

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