Judith B Posted March 6, 2015 Report Share Posted March 6, 2015 So, this is a very trivial question but I can't find a proper answer anywhere. What is the difference between an underglaze and a glaze? From what I read online, it seems that it is pretty similar, only a small variation of some chemicals. But which ones? I understand that slips are made of clay and stains but I can't quite figure it out for underglazes and glazes. Where I work, we have underglazes and glazes and sometimes people ask the difference... And I always feel very stupid ^^. I know that we have to glaze the underglazes but it technically doesn't make much sense to me Link to comment Share on other sites More sharing options...
Chris Campbell Posted March 6, 2015 Report Share Posted March 6, 2015 Underglazes are for decorating ... They do not seal the surface or make it food safe. They will not prevent stains or color absorption. They are most often used under glazes. Glazes when properly matched to the clay and properly fired, seal the surface with a glass like layer making the wares suitable for utilitarian use. A glaze that does not move much during firing can be used for decorating but an underglaze cannot be used as a glaze. Link to comment Share on other sites More sharing options...
Mysteria Posted March 6, 2015 Report Share Posted March 6, 2015 Thanks for asking the question, Judith and Chris for clarifying! I was asked this question by some beginners recently and wasn't quite sure how to explain the difference Link to comment Share on other sites More sharing options...
jolieo Posted March 6, 2015 Report Share Posted March 6, 2015 Underglazes are the color. They are similar to oxides, except oxides are reactive to the chemistry around them, either in the clay or the glaze or both. Underglazes are made non reactive. They are also usually the color they will be albeit not the same intensity. They can be left unglazed, but I think they are just decorative at that point. They probably would be in danger of abrasion or wear. A glaze is almost a glass that is melted on to the ceramic in either it's green ware state or its bisque state.glass has to be compatible in what shrinkage and expansion each glass has .if too far apart , they come apart. Clay and glaze have those same issues, plus other issues to do with the clay body. So glazes don't always work even if They are fired to the same cone . Some clays have fluxes, or chemicals that become fluxes in them and they become self glazing. Wood fired kilns can glaze the vessels in the kiln through a deposit of wood ash on the vessels. Adding salt to kiln (not electric unless made for it, ruins the elements) glazes it too. Since clays and glazes have a lot of the same things in them, clays can almost become glazes if chemicals are introduced . The purpose of bisqueing is so that the ceramic is still able to accept the colorant and the glaze but not be as fragile as greenware. Once the vessel has been fired to the point of maturity ( so it is completely fused on a molecular level) It is all but impossible to put glaze on (. I don't know about oxides or underglaze- perhaps they might take if there was tooth). Glaze would slide off I think. Dealing with clay is chemistry or alchemy or both. I think I might learn a few chants to get thing more on my side. Nah it would probably backfire! Jolie Link to comment Share on other sites More sharing options...
Sunny Posted March 6, 2015 Report Share Posted March 6, 2015 Underglazes are good for detail work. I paint my detail work on greenware than fire to bisque 04. That way when I put my glaze on, it won't pull the underglaze off. Link to comment Share on other sites More sharing options...
Chilly Posted March 6, 2015 Report Share Posted March 6, 2015 Try putting two glazes side-by-side to produce detailed pictures then repeat with under-glazes. Fire both and see the difference. Under-glazes do not move or blend with each other. Most glazes (I know not all) will bleed into each other, or one will move over the other, or they will slide slightly down a vertical surface. For me, under-glazes are for when you want more than one colour on a piece, glazes are for single-colour or "doesn't matter" if they run together. Link to comment Share on other sites More sharing options...
Mug Posted March 6, 2015 Report Share Posted March 6, 2015 The descriptions above are more accurate, but to keep things simple, someone said to me an underglaze is like colored slip and a glaze is more of a glass coating. It's prety much the way I think of it to this day Link to comment Share on other sites More sharing options...
Cat Woman Posted March 6, 2015 Report Share Posted March 6, 2015 So, are there recipes to make your own underglazes? I have lots of books for making glazes but they don't have recipes for underglazes. I have lots of Mason stains and clear glaze so this sounds like a fun thing to do if I knew how. Link to comment Share on other sites More sharing options...
bciskepottery Posted March 6, 2015 Report Share Posted March 6, 2015 So, are there recipes to make your own underglazes? I have lots of books for making glazes but they don't have recipes for underglazes. I have lots of Mason stains and clear glaze so this sounds like a fun thing to do if I knew how. Check the handouts on engobes and underglazes and on Mason stains at Vince Pitelka's website: http://iweb.tntech.edu/wpitelka/syllabi-handouts/handouts-info.htm You may also find recipes in the various Robin Hopper books and other sources. Link to comment Share on other sites More sharing options...
Cat Woman Posted March 6, 2015 Report Share Posted March 6, 2015 So, are there recipes to make your own underglazes? I have lots of books for making glazes but they don't have recipes for underglazes. I have lots of Mason stains and clear glaze so this sounds like a fun thing to do if I knew how. Check the handouts on engobes and underglazes and on Mason stains at Vince Pitelka's website: http://iweb.tntech.edu/wpitelka/syllabi-handouts/handouts-info.htm You may also find recipes in the various Robin Hopper books and other sources. Thank you. I'm just starting back up in pottery after a few years off after a broken wrist and a move to Texas. I had been going to a local studio where we fired to cone 10 reduction. I now have my own kiln and will be firing to cone 6 oxidation. The problem is I have left over cone 10 clay that I want to fire before starting on cone 6 but I don't want to invest heavily in cone 10 glazes. I have a clear glaze that will fire from cone 5-10 so would like to do some slip work and now the idea of the underglaze is intriguing. Lots to learn - which makes it fun. Link to comment Share on other sites More sharing options...
neilestrick Posted March 6, 2015 Report Share Posted March 6, 2015 So, are there recipes to make your own underglazes? I have lots of books for making glazes but they don't have recipes for underglazes. I have lots of Mason stains and clear glaze so this sounds like a fun thing to do if I knew how. I think commercial underglazes are well worth the money. If you get the right brand (I use Speedball), the colors are stable at cone 6, they brush on very nicely, and can be applied at any stage- wet, leather hard, bone dry, or bisque. Personally, I like to apply to bisque since they dry quickly that way, and I the work isn't as fragile at that stage. Link to comment Share on other sites More sharing options...
Judith B Posted March 7, 2015 Author Report Share Posted March 7, 2015 The descriptions above are more accurate, but to keep things simple, someone said to me an underglaze is like colored slip and a glaze is more of a glass coating. It's prety much the way I think of it to this day So, Underglazes do contain some clay? I wasn't sure. I know how to use udnerglazes and glazes but I was wondering about the difference in composition. Thank you for all your answers Link to comment Share on other sites More sharing options...
neilestrick Posted March 7, 2015 Report Share Posted March 7, 2015 Commercial underglazes fuse more than a slip would. That's why they can be used on bone dry clay and bisque ware without flaking off. They can be fired in bisque and still be porous enough to take glaze. But they don't go into melt like a glaze. They are quite versatile. Most home made underglazes are either more of a colored slip that has to be applied to leather hard pots, or are just stains with a frit binder and work best on bisque. I was working on a new commercial underglaze formula when I left my last tech job, and I can tell you that they are fairly complex. It's a fine balance to get them to fuse to leather hard, bone dry or bisque, but still be porous enough to take glaze after bisque firing, to play nicely with glazes, and to brush well. Link to comment Share on other sites More sharing options...
JamesMeline Posted February 14, 2020 Report Share Posted February 14, 2020 On 3/5/2015 at 8:00 PM, jolieo said: Underglazes are the color. They are similar to oxides, except oxides are reactive to the chemistry around them, either in the clay or the glaze or both. Underglazes are made non reactive. They are also usually the color they will be albeit not the same intensity. They can be left unglazed, but I think they are just decorative at that point. They probably would be in danger of abrasion or wear. A glaze is almost a glass that is melted on to the ceramic in either it's green ware state or its bisque state.glass has to be compatible in what shrinkage and expansion each glass has .if too far apart , they come apart. Clay and glaze have those same issues, plus other issues to do with the clay body. So glazes don't always work even if They are fired to the same cone . Some clays have fluxes, or chemicals that become fluxes in them and they become self glazing. Wood fired kilns can glaze the vessels in the kiln through a deposit of wood ash on the vessels. Adding salt to kiln (not electric unless made for it, ruins the elements) glazes it too. Since clays and glazes have a lot of the same things in them, clays can almost become glazes if chemicals are introduced . The purpose of bisqueing is so that the ceramic is still able to accept the colorant and the glaze but not be as fragile as greenware. Once the vessel has been fired to the point of maturity ( so it is completely fused on a molecular level) It is all but impossible to put glaze on (. I don't know about oxides or underglaze- perhaps they might take if there was tooth). Glaze would slide off I think. Dealing with clay is chemistry or alchemy or both. I think I might learn a few chants to get thing more on my side. Nah it would probably backfire! Jolie Someone Stole this answer and posted it to Quorahttps://www.quora.com/What-s-the-difference-between-glaze-and-underglaze they didn't even bother to change anything. Only deleted a couple of lines. Link to comment Share on other sites More sharing options...
Min Posted February 15, 2020 Report Share Posted February 15, 2020 @JamesMeline, we will contact @jolieo and let her know what happened, it will be up to her how she proceeds with this. I do believe that the person who took her post from here and posted it on Quara was called out by a fellow Quara member as it links back to the original thread here where she copied the thread from. Long odds but @jolieo and the person on Quara could be one and the same. Welcome to the forum. Link to comment Share on other sites More sharing options...
Juliagoolia Posted February 15, 2020 Report Share Posted February 15, 2020 I love this thread as the slips/englobes/underglaze has confused me in the past. I'm also a fan of speedball and recently tried layering underglaze on top of a glaze, and then letting a runny glaze drag it down. Based on a combo in Gabriel Kline's Amazing Glaze. Link to comment Share on other sites More sharing options...
Chele Posted May 1, 2021 Report Share Posted May 1, 2021 On 2/14/2020 at 12:28 PM, JamesMeline said: Someone Stole this answer and posted it to Quorahttps://www.quora.com/What-s-the-difference-between-glaze-and-underglaze they didn't even bother to change anything. Only deleted a couple of lines. I am so sorry that this was plagiarized. That's just rude! Nonetheless, I really appreciate it being posted here again because I somehow missed it before. Thank you! Link to comment Share on other sites More sharing options...
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