Susan McHenry Posted January 29, 2021 Report Share Posted January 29, 2021 Can anyone offer insight into why I’m getting what look like pin holes on the surfaces of my freshly glazed pots? These little pin holes happen on all my pots, but only on areas that have bisque fired slip underneath. I have to rub out the surface where these pin holes appear since my clear glaze is stable. I’d love to be able to solve this problem. Thanks for your help! Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted January 30, 2021 Report Share Posted January 30, 2021 Hi @Susan McHenry, I'm taking the liberty of editing your title to add more detail to get some more eyes on the problem for you. It's best to summarize your question for the title, rather than using your name. Regarding the pinholes, do you wash or dampen your bisque before glazing? What's the glaze recipe? Perhaps there's something in the recipe that's contributing. Link to comment Share on other sites More sharing options...
Min Posted January 30, 2021 Report Share Posted January 30, 2021 I used to have the same problem when I used a red underglaze that was bisque fired on. I think what was happening was the underglaze had a different porosity than the parts of the pot without underglaze. When the pot was dipped in the glaze there wasn't a good even lay down of the glaze and air was expelled from the underglazed areas causing the pinholes. I got around this by spraying the pots with this particular red underglaze but that's not necessarily a solution for you. Whats in the slip? Other thought would be like Callie said and dampen the pot prior to glazing. Link to comment Share on other sites More sharing options...
Susan McHenry Posted January 31, 2021 Author Report Share Posted January 31, 2021 I damp sponge all my bisqueware before glazing. Recipe is: Gerstley borate 28 Nepheline Syenite 46 EPK 6 Silica 20 Link to comment Share on other sites More sharing options...
Susan McHenry Posted January 31, 2021 Author Report Share Posted January 31, 2021 I’ve heard that some folks wet sand their bisqueware before glazing. I’m going to try this on my next batch. Well keep you posted! Thanks for the tips! Link to comment Share on other sites More sharing options...
oldlady Posted January 31, 2021 Report Share Posted January 31, 2021 some folks? maybe 2 in the entire world. why would anyone do that? Link to comment Share on other sites More sharing options...
Bill Kielb Posted January 31, 2021 Report Share Posted January 31, 2021 1 hour ago, Susan McHenry said: I damp sponge all my bisqueware before glazing. Recipe is: Gerstley borate 28 Nepheline Syenite 46 EPK 6 Silica 20 Hmmm, interesting recipe. Is there something you particularly like about this and do you feel it is durable? High levels of Gerstley can cause issues, the amount of boron indicates this probably will melt at cone 04 and not having 10-20% clay can mean suspension issues but with this much Gerstley might not be noticeable. Additionally the flux ratio is well outside known likely durable glazes and the amount of silica and alumina is on the high end for cone six. Might be a great recipe in the end though, is there something you like in particular about it? Link to comment Share on other sites More sharing options...
Susan McHenry Posted February 1, 2021 Author Report Share Posted February 1, 2021 I like the satiny appearance. I hate super shiny glazes. I fire it to cone 1 with a slow cooling cycle. Maybe I should rethink my glaze? Link to comment Share on other sites More sharing options...
Bill Kielb Posted February 2, 2021 Report Share Posted February 2, 2021 3 hours ago, Susan McHenry said: Maybe I should rethink my glaze? Lots of satin glazes. Glazes with large amounts of Gerstley can create application problems in slow drying and of course the inevitable pinholes as the air slowly bubbles up through it. Is your clay cone 1 or are you just firing it that way for the finish? Link to comment Share on other sites More sharing options...
Susan McHenry Posted February 2, 2021 Author Report Share Posted February 2, 2021 I’m using red earthenware and firing hotter to tighten the clay body. I love the durability and clay body color at this temp. Link to comment Share on other sites More sharing options...
oldlady Posted February 2, 2021 Report Share Posted February 2, 2021 if you do change your clay and want to fire at cone 6, there are lots of glazes that will probably suit you. you might want to look at a very good but simple book that was written by a ceramic engineer and his wife. it is called "Getting into pots" and was published in 1976. see pages 123 to 127 for an easy way to mix your own glazes. Link to comment Share on other sites More sharing options...
PeterH Posted February 2, 2021 Report Share Posted February 2, 2021 24 minutes ago, oldlady said: if you do change your clay and want to fire at cone 6, there are lots of glazes that will probably suit you. you might want to look at a very good but simple book that was written by a ceramic engineer and his wife. it is called "Getting into pots" and was published in 1976. see pages 123 to 127 for an easy way to mix your own glazes. Nancy Wettlaufer: Getting into pots 2nd hand from 5$, new from 23$ tinyurl.com/3xf4ldtu Link to comment Share on other sites More sharing options...
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