Marie Lu Posted January 24 Report Share Posted January 24 Dear community, I hope I am uploading my question in the right section, if not feel free to move it. So I made a mug about 2,5 years ago that I gave to my sister. Yesterday she told me that the mug cracked by the handle (see picture) although she does not recall anything happen to it. Looking at it I feel like it most be an expansion issue that must have caused the crack to happen. I am just surprised that this would happen after such a long time! I am self taught and have been making pottery on and off for about 10 years now. In the last year or two I also started making my own glazes. Pottery is really complex in my opinion and producing something that is not of great quality is always something I worry about a bit and even sometimes make me question if I should pursue pottery it all since I learned everything myself. So having something like this happen, a mug breaking years after making it, really makes me question how I can unsere that my pottery is good and durable. Do you guys also think it is an expansion/stress problem that caused the crack? And do you have any methods beside the ice water/boiling water test to check for good glaze fit? Thanks for taking the time to read my post. Have a great day! Marie Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted January 24 Report Share Posted January 24 (edited) +1 for caring! My experience - this is likely a joint failure, not necessarily glaze related. I like you, worried about the same things and once I had a similar handle crack decided to knock the handles off on a handful of my bisqued mugs and even several glazed. What I found was some handles were attached so securely that the parent material or clay would fail and the joint material remain intact on only the best made joints. From that point on - I spent quite a bit of time on making sure to compress these joints very firmly during construction to be sure the material around and the joint itself was every bit as dense as the parent clay. When I did this, the joint would be as strong as the parent clay which was the best that could be done for that joint. If I needed a stronger joint for extra rough use, then it became larger but always paying extra attention that the joint was fully compressed and attached well. A few more well compressed attachments later, knocking the handles off revealed the parent clay material would now fail before the joint actually would. From that point on I never had a failure, and often when tested by impact, the side of the mug would fail and not the joint. Good glaze helped, but glaze is too brittle to save a weaker made joint. Never had a critical joint fail after that. Typical well made and well attached joint below. This joint is fairly large but these are very custom mugs. It takes significant force but the cup will fail before this joint will. Always compress critical joints so the material is uniform strength was the lesson for me. Edited January 24 by Bill Kielb rox54 and Rae Reich 2 Quote Link to comment Share on other sites More sharing options...
Pres Posted January 24 Report Share Posted January 24 When working with students in the early years I had quite a bit of trouble with students not getting tight joins in slab construction, coil or when joining handles. At the time we were using slip as I did not know anything else for a proper join. I was teaching about compression to make certain the pieces stayed together, but still had problems with the joins students made. In the late 80's I came across reference to "magic water" in a Ceramics Monthly. It took me a while to decide to try it, but when I did I found that overnight my problems with joins in the student pots dropped dramatically. I also found that the joins were cleaner, and overall there were fewer gaps in all of the constructions. If you are not using it. . . I would recommend it. best, Pres Bill Kielb and rox54 2 Quote Link to comment Share on other sites More sharing options...
Marie Lu Posted January 25 Author Report Share Posted January 25 @Pres thank you so much for your advice. I never heard of “magic water” but would like to try it. Do you recommend a specific recipe? Best, Marie Quote Link to comment Share on other sites More sharing options...
Marie Lu Posted January 25 Author Report Share Posted January 25 @Bill Kielb thank you so much for your response. You made a good point and now that I think about it I definitely have noticed when wet sanding my bisque that sometimes there would be little bubbles coming through the water, meaning there is space between the handle and mug. I always thought that this is probably not a huge deal since the glaze will make handle and mug stick together super well but I guess I was wrong… I always worried way more about clay body and glaze fit and making durable good glazes but I guess good construction is just as important. Your handle certainly looks like it will never come off that mug! Thanks again for your input. Alle the best, Marie Bill Kielb and Rae Reich 2 Quote Link to comment Share on other sites More sharing options...
Pres Posted January 25 Report Share Posted January 25 The original recipe for Magic Water by Lana Wilson is: 1 gallon water 3 Tablespoons liquid sodium silicate 1 1/2 teaspoon soda ash -OR- 1 gallon water 9.5 grams sodium silicate 3 grams soda ash You will find many variations of this on the web if you do a search. I use the one listed above. best, Pres Babs and Rae Reich 2 Quote Link to comment Share on other sites More sharing options...
Mark C. Posted January 25 Report Share Posted January 25 My guess is the handle got bumped and hence the crack . If it was fine for years of use then cracked it got bumped . If it cracked right away(1st month) its a poor connection Pres and Babs 2 Quote Link to comment Share on other sites More sharing options...
Marie Lu Posted January 29 Author Report Share Posted January 29 @Pres thank you, I will give it a try! @Mark C. I think you guys are right and I am kinda relived because I feel like a poor connection is easier fixed than a clay/glaze issue. Pres 1 Quote Link to comment Share on other sites More sharing options...
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