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Showing results for tags 'deflocculant'.
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Hi all, Second time posting here and I’m hoping you can help! Hopefully this is the right place to be for a troubleshooting question like this. Im currently working from a recipe for Val Cushing’s Cone 6 Porcelain Slip. grolleg: 15% tile 6: 15% Epk: 3% om4: 10% flint: 25% neph sy: 30% gerstley borate: 2% —————————— Sodium silicate: .0028% calgon: .0005% When I mixed this before, as now, I subbed the deflocculants with Darvan. I mixed it successfully then, but I’m currently have difficulty. I know that darvan generally subs for sodium silicate at 2-1, so bearing that in mind, that’s where I started. I kept adding darvan in small 5g increments up to 100g in a 10000g recipe. That seems like far too much, but maybe I’m wrong? I feel like I’m on the other side of that deflocculation bell curve some how and missed my mark. Every time I come back to the studio the slip is gelled thick but never settled and never develops a skin. When I’ve added more darvan, the slip temporarily thins, but seems to rebound to being too thick the next day. Can the casting process indicate overdeflocculation? If so, in what ways? What should I be looking out for other than settling and a skin in my bucket? Can anyone offer any advice on this recipe or deflocculants? I’ve been doing some hard research and testing and can’t nail it down. My current gravity is measuring at 1.71, so I’m hesitant to add more water, since according to some other online sources I should be aiming between 1.7 and 1.8. I’m wondering if I should throw caution to the wind and say “this slip just needs more water than most”. Ive mixed this slip before with great success two years ago. I have no clue what I did right then. Dumb luck haha. Any suggestions or advice would be greatly appreciated. Thanks!
Hello, I am fairly new to slip casting (about 9 months), and have been trying to learn as much possible through books and videos. I haven't delved into making my own slip yet, instead I have been using Dover Slip from Miller (Laguna). It is a Cone 6 White Stoneware. I am having some issues with the slip: 1) A film forms on top the slip after sitting in the mold for about 10 minutes. 2) When I do the hand dip test no webbing is forming at all. 3) I believe the Specific Gravity is 1.8 (which should be right) I measured out 100ml and it weighs 180 grams. 4) It is pretty thick, pours out of the mold poorly leaving behind some gunk on the rim of the mold (makes for an uneven lip of my tableware) 5) It doesn't pull from the mold well, sometimes even 2 hours later I still can't get a simple cup out. Just for some addition information the room I am casting in lately has been around 85-95 degrees F, with pretty high humidity. What I am trying to figure out is if I need to add more deflocculant or if the slip has come over deflocculated from the factory, or perhaps I need to add more water. Thanks for the input. -Matt
Thought I'd share a success story here with my Terra Sigillata recipe. Everything I've ever read says that you need sodium silicate or sodium carbonate but it seems that Tetrasodium EDTA - aka Jet-Dry works as well. 3 parts Clay 1 part water 2 teastpoons Jet-Dry I used a small bottle to mix up a test batch as I wasnt sure that it would work at all. Previous attempts at using Calgon were unsuccessful as I read that the old recipe containing phosphates was changed. So, if you dont have sodium silicate or sodium phosphate handy you can give this a try and see if it works for you. Full post here - https://dreamsofearth.wordpress.com/2015/05/24/terra-sigillata/