Flammingo Studio Posted October 30, 2022 Report Share Posted October 30, 2022 Help! I have always bought casting slip from the same supplier and it has worked like a charm. I decided to start casting again and I bought the same casting slip and the slip is very runny. I will not set up in my molds. The shop owner was of no help and I have tried to research the solution. Can epsom salt dissolved in water work as a flocculant to thicken this low fire casting slip?? Thanks for any suggestions Quote Link to comment Share on other sites More sharing options...
Min Posted October 30, 2022 Report Share Posted October 30, 2022 Hi and welcome to the forum! I would start by measuring the specific gravity of the casting slip with an accurate scale. Should be somewhere between 1.72 and 1.80. If it's below 1.72 I would let some of the water evaporate off it until it's in that range and try casting with it again. If you stir it up with your hand does it web between your fingers for a few seconds when you take your hand out the slip and spread your fingers apart? Doesn't need to be as much as this but similar too. Couple questions, is the shop owner the person who made the casting slip or is if from a different manufacturer that you could contact? If so ask which talc they are now using in it and what specific gravity they recommend. Quote Link to comment Share on other sites More sharing options...
Flammingo Studio Posted October 30, 2022 Author Report Share Posted October 30, 2022 Good question on manufacturing. I don't think they make their own but I will find out tomorrow. I had another potter tell me she always weights her slip before casting. That 100ml should weigh about 175 grams. I checked mine, several times over, and 100ml weights 95 grams. Yikes, this is why I have always bought slip so I don't have to mess with the calculations of science Quote Link to comment Share on other sites More sharing options...
Min Posted October 30, 2022 Report Share Posted October 30, 2022 29 minutes ago, Flammingo Studio said: I checked mine, several times over, and 100ml weights 95 grams. With all due respect it can't be 95 grams. 100ml of water weighs 100 grams. Every material added to the water in casting slip has a higher specific gravity than water. Your friends 1.75 makes sense, perhaps they could use their scales for you and weigh some out? PeterH 1 Quote Link to comment Share on other sites More sharing options...
PeterH Posted October 31, 2022 Report Share Posted October 31, 2022 20 hours ago, Min said: With all due respect it can't be 95 grams. 100ml of water weighs 100 grams. Every material added to the water in casting slip has a higher specific gravity than water. Your friends 1.75 makes sense, perhaps they could use their scales for you and weigh some out? Can you repeat your measurements of SG -- for both the slip and just water -- and report your raw data as well as your calculated SG. Making measurements for two liquids may help us discover where the error is occurring. Min 1 Quote Link to comment Share on other sites More sharing options...
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