Brooklyn Mom Posted January 10, 2021 Report Share Posted January 10, 2021 Hello all, I do slip casting in porcelain using a recipe I found online and having issues with performance. Bowls cracked at bottom when coming into contact with hot soup, edges get chipped easily...Does anyone have a cone 6 tried & true porcelain slip for functional ware they want to share? One with proven market success that withstand everyday kitchen use? I’d REALLY appreciate this! Thank you in advance. Xo Link to comment Share on other sites More sharing options...
liambesaw Posted January 10, 2021 Report Share Posted January 10, 2021 It sounds more like a glaze issue to me. Glaze fit issues can cause cracking especially if there's a different glaze in the inside and outside. If it were a clay body issue you'd see it in the bisque firing in my experience. Link to comment Share on other sites More sharing options...
Min Posted January 10, 2021 Report Share Posted January 10, 2021 2 hours ago, Sig Student said: I do slip casting in porcelain using a recipe I found online Recipe? 2 hours ago, Sig Student said: Bowls cracked at bottom when coming into contact with hot soup, edges get chipped easily Pictures? Plus glaze recipe? Link to comment Share on other sites More sharing options...
Brooklyn Mom Posted January 10, 2021 Author Report Share Posted January 10, 2021 Hi Min, This is the recipe. It’s from an artist and I think I should change so it’s truly functional instead of trying to fix it. Thank you! For a 5 gallon bucket of slip: Material Amountn cc Water 2 Gallons Darvan 7 68 grams OM 4 Ball Clay 10 lbs EPK 5 lbs Grolleg 5 lbs G200 Feldspar 5 LLP Nepheline Syenite 5 lbs Silica (Flint) 7.5 lbs Link to comment Share on other sites More sharing options...
Brooklyn Mom Posted January 10, 2021 Author Report Share Posted January 10, 2021 12 hours ago, liambesaw said: It sounds more like a glaze issue to me. Glaze fit issues can cause cracking especially if there's a different glaze in the inside and outside. If it were a clay body issue you'd see it in the bisque firing in my experience. Thanks Liam. I used the amaco satin. There are also cutlery marks but I decided to make my own glaze and now in the process of doing so. I feel like I’m starting over, but better now than later. Link to comment Share on other sites More sharing options...
Min Posted January 10, 2021 Report Share Posted January 10, 2021 I compared your recipe to quite a few that I've tested, including one from Andrew Martin. (he has a great book on slip casting if you need one) Have a look at the formulas (below the recipes), I'm not seeing anything thats really out of whack. If it casts okay I'ld be looking at other causes for the chipping and crazing. For both I would confirm that the kiln is firing to a full cone 6, verify with witness cones on each shelf. Depending on what qualities of the glaze is contributing to the type of matte glaze it is makes a difference to the scratch resistance of the fired glaze. Cutlery marking could just be from underfiring also. For interior surfaces of functional pots a gloss glaze is (usually) preferred for scratch/cutlery marking resistance. It's hard to tell in your picture but it looks like the rim on one of the black pots is quite thin plus the edges look like they could be rounded over more. Sharper angles on rims tend to chip more than rounded rims. Link to comment Share on other sites More sharing options...
neilestrick Posted January 10, 2021 Report Share Posted January 10, 2021 Have you done an absorption test? I'm thinking the Neph Sye is too low, and you have a lot of unbound silica. My rule of thumb is that feldspar = flint, possibly more for cone 6. Link to comment Share on other sites More sharing options...
liambesaw Posted January 10, 2021 Report Share Posted January 10, 2021 31 minutes ago, neilestrick said: Have you done an absorption test? I'm thinking the Neph Sye is too low, and you have a lot of unbound silica. My rule of thumb is that feldspar = flint, possibly more for cone 6. He's got g200 there too Link to comment Share on other sites More sharing options...
neilestrick Posted January 10, 2021 Report Share Posted January 10, 2021 34 minutes ago, liambesaw said: He's got g200 there too Totally misread that with the way it's spaced! Link to comment Share on other sites More sharing options...
Brooklyn Mom Posted January 11, 2021 Author Report Share Posted January 11, 2021 Min Thanks for taking the time to look/compare recipes -that is very kind You are right about the underfiring. I need to change the elements. I do have the book by Andrew Martin, but he too is an artist. I’m not attached to the recipe I used. It was the first slip I ever made and now looking for one with proven record in functional tableware, a porcelain slip recipe that someone has been using g for functional ware themselves and that it has passed the test of time/wear. I’m also making terra sig AND my own glazes. I would like the slip recipe to be recommended. Do you do commercial tableware? Today, I went ahead and mixed L3778G from Tony Hansen digital fire. Here is the link https://insight-live.com/insight/share.php?z=tgsPMxNsAP Link to comment Share on other sites More sharing options...
liambesaw Posted January 11, 2021 Report Share Posted January 11, 2021 If it helps at all, I've used the first and second recipe here: https://claybucket.com/recipes/casting-slips/ The first recipe is the casting slip, the second recipe is the throwing body that matches it perfectly for attachments. The only change I made was to use veegumT instead of bentonite since I was going for a super white porcelain. Was tight at cone 6, no absorption and quite durable. I used it to make coffee pour over carafes. Link to comment Share on other sites More sharing options...
Brooklyn Mom Posted January 11, 2021 Author Report Share Posted January 11, 2021 Thanks Min! I do have the book by Andrew Martin but he too is an artist. You might be right about the underfiring. I need to change the elements. Re the slip: thanks for taking the time to look/compare recipes -that is very kind I’m looking for a porcelain slip recipe that someone has been using g for functional ware themselves and that it has passed the test of time/wear. Today, I went ahead and mix Link to comment Share on other sites More sharing options...
Min Posted January 11, 2021 Report Share Posted January 11, 2021 Check your pm. Link to comment Share on other sites More sharing options...
Brooklyn Mom Posted January 16, 2021 Author Report Share Posted January 16, 2021 On 1/10/2021 at 11:03 PM, Min said: Check your pm. Thanks Min! You are the kindest. I decided to go with Tony Hansen’s L3778G. I tried it for the first time yesterday. It’s casting really nice and it comes out of the mold much faster than my previous as it has very little water. I have not yet fired it but so far so good. I’ll keep you posted Link to comment Share on other sites More sharing options...
Brooklyn Mom Posted January 16, 2021 Author Report Share Posted January 16, 2021 On 1/10/2021 at 8:24 PM, liambesaw said: If it helps at all, I've used the first and second recipe here: https://claybucket.com/recipes/casting-slips/ The first recipe is the casting slip, the second recipe is the throwing body that matches it perfectly for attachments. The only change I made was to use veegumT instead of bentonite since I was going for a super white porcelain. Was tight at cone 6, no absorption and quite durable. I used it to make coffee pour over carafes. Hi Liam, I’m sorry for the delay -i was busy making slips and glazes Thank you for the suggestion-it’s really good to have the equivalent to Dylan Beck’s recipe. I decided to try Tony Hansen’s L3778G. Waiting the see the fired results in a week or do. Link to comment Share on other sites More sharing options...
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