Lucy P. Posted November 11, 2021 Report Share Posted November 11, 2021 I started making my slip for pouring but I keep having the same issue with every batch I make. When I stir it, it becomes nice and smooth with the cream consistency. After pouring it into a plaster mold and waiting for about 15min, it becomes very 'chunky'. It's too thick to pour it back out from the mold. What am I doing wrong? Is it because of the wrong ratio of the slip, or is it because of too much darvan? I used 11g of darvan811 for 1gallon of slip (this is what my professor told me back in the day when I was in the ceramic class). I measured the gravity and it was around 1.76. I used 40% water of the dry clay. And also, could you share some 04 slip recipes for pouring if you have any awesome ones!? Thank you for your time! Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted November 11, 2021 Report Share Posted November 11, 2021 Sounds like it is thixotropic so it will gel when it stops being agitated. You could try shaking/agitating the mold a little before trying to pour out. Not sure if more or less darvan would help this problem. Link to comment Share on other sites More sharing options...
Jeff Longtin Posted November 11, 2021 Report Share Posted November 11, 2021 It's been my experience that a slip with too much water, stays thin., whereas a slip with too much deflocculant, thickens as it sits. I would suggest adding a little water and seeing if that helps. Shaking the mold - I've been in this situation and I've tried shaking the mold. What this does, unfortunately, is create a vacuum that causes the sides of the piece to get sucked in. I've found it easiest just to accept the mistake and reclaim the clay however you prefer. (I put a bunch of bone dry shards in a bucket of water and create a reclaim batch.) Link to comment Share on other sites More sharing options...
Lucy P. Posted November 11, 2021 Author Report Share Posted November 11, 2021 7 hours ago, High Bridge Pottery said: Sounds like it is thixotropic so it will gel when it stops being agitated. You could try shaking/agitating the mold a little before trying to pour out. Not sure if more or less darvan would help this problem. I tried to shake the mold but it wouldn't do anything to the slip. If I touch it, it becomes very liquid but then goes back to the 'gel' form within a few seconds. Myabe I added too much darvan... Link to comment Share on other sites More sharing options...
Lucy P. Posted November 11, 2021 Author Report Share Posted November 11, 2021 2 hours ago, Jeff Longtin said: It's been my experience that a slip with too much water, stays thin., whereas a slip with too much deflocculant, thickens as it sits. I would suggest adding a little water and seeing if that helps. Shaking the mold - I've been in this situation and I've tried shaking the mold. What this does, unfortunately, is create a vacuum that causes the sides of the piece to get sucked in. I've found it easiest just to accept the mistake and reclaim the clay however you prefer. (I put a bunch of bone dry shards in a bucket of water and create a reclaim batch.) I added a little more water but seems like it doesn't really help... I think I added too much darvan. I think added more than 13g of darvan into this 1 gallon slip. Would it be too much? This is my first time making slip, so I can't really tell. I only see people saying "add just a little bit of darvan" but idk how much that 'a little bit' is lol. I started with 11g of darvan and then added more in the end because I thought it's not enough. I wish I knew the specific amount of darvan I need for 1 gallon slip. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted November 11, 2021 Report Share Posted November 11, 2021 I found this on digital fire https://digitalfire.com/article/understanding+the+deflocculation+process+in+slip+casting Seems to be saying you have too little darvan in there. You could test by removing a cup of slip and adding more darvan to one and more clay to the other and see if you can get one that works. Also http://www.ceramicsmadeeasy.com/print/52/index.html seem to be adding 16.3 grams to a 10lb or around 1 gallon of slip which is more than you have added. Link to comment Share on other sites More sharing options...
Lucy P. Posted November 12, 2021 Author Report Share Posted November 12, 2021 6 hours ago, High Bridge Pottery said: I found this on digital fire https://digitalfire.com/article/understanding+the+deflocculation+process+in+slip+casting Seems to be saying you have too little darvan in there. You could test by removing a cup of slip and adding more darvan to one and more clay to the other and see if you can get one that works. Also http://www.ceramicsmadeeasy.com/print/52/index.html seem to be adding 16.3 grams to a 10lb or around 1 gallon of slip which is more than you have added. WOW!! Thank you so much for all these precious helpful information! I was so close to toss them out and now I know that they are actually fixable! I will add more darvan and see if there's any improvement. Thank you so much again!!! You are the salt and light of my life <3 Link to comment Share on other sites More sharing options...
Mark C. Posted November 12, 2021 Report Share Posted November 12, 2021 Davan 7 is what we used for years in a larger slip operation-not familiar with 811? Link to comment Share on other sites More sharing options...
PeterH Posted November 12, 2021 Report Share Posted November 12, 2021 You may also find this handout from Alfred university of interest, as it highlights some of the issues involved. Determining Dispersant Additions for Casting Slips https://tinyurl.com/3tbp2wka PS Only mentioning as a thought experiment. Link to comment Share on other sites More sharing options...
Lucy P. Posted November 13, 2021 Author Report Share Posted November 13, 2021 On 11/12/2021 at 11:33 AM, PeterH said: You may also find this handout from Alfred university of interest, as it highlights some of the issues involved. Determining Dispersant Additions for Casting Slips https://tinyurl.com/3tbp2wka PS Only mentioning as a thought experiment. Thank you so much for sharing this information! I'm definitely trying this testing method! Link to comment Share on other sites More sharing options...
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