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- Mar 07 2013 11:11 AM
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Posted 6 Mar 2013What deflocculant are you using? Sodium silicate? All clay bodies deflocculate differently, depending on what's in them. So a general casting slip recipe won't necessarily be correct for your clay body. It'll take some tweaking. I would first try drying out the molds better, then stiffen up the slip.
Been using Sodium Silicat mixed 50/50 with water, per the manufacturers directions.
Posted 6 Mar 2013Are you deflocculating the slip? Is the mold dry and clean?
I have mixed the slip according to the manufacturers specs. With a specific gravity of 1.76. I have tried 1.79 and also 1.72 spec. gravity and have been having similar results.
The Slip does tend to "settle" or dry quickly. If I leave it for an hour or so, there is more firm "skin" layer that develops on the surface, usually about 1/2" thick. I just mix that in to the slip and strain it before pouring and it doesn't seem to be effecting the consistency of the slip.
The molds are dry and slightly warm to the touch, similar to a bone dry piece of clay. Perhaps I need to leave them dry for longer than 24 hours. The humidity has been a little hi over here in Southern Calif.
I am fairly new to slip casting, so any advice is appreciated.
Posted 6 Mar 2013Have you given them time to dry somewhat?
I have tried letting them dry over night, and that didn't work. The details caused it to crack and tear itself apart. I have also tried letting them dry for about 1 hour until the slip was leather hard, or slightly beyond, and still they stick.
Is just a matter of finding the ideal drying time through trial and error?
Posted 24 Oct 2012I think I may have figured it out. I think its a combination of the glaze settling out as well as adding a little too much water to the slightly thick glaze. I am going to try having the students put an extra coat on and see if that helps.
@TJR I usually have a shelf dedicated to the glazed projects and then the bisque-ware on separate shelves. I am going to try the glazed ware on the top to see if this makes a difference.
Posted 19 Oct 2012Great! Thanks Mark. I'll give him a call today.
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