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Question about underglazing


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I have made some plates with a hump mold. I didn't put a foot on them and have decided to glaze only the inside to have a place for the glaze to stop. My question is this: Can I use an underglaze when it is green on the bottom, fire to bisque, glaze the inside and on the glaze fire be able to set the plate bottom side down on my kiln shelves and not have them stick to the shelves? Thank you for your wisdom! 

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Underglazes contain flux.  They flux at different temperatures, depending on the color of the underglaze, so I avoid putting underglaze on any area that will be touching  the kiln shelf (or touching any other part of the piece, like the flange of a lid) - it will probably stick,  When I make a bowl without a foot ring,  I leave a circle on the bottom where it will touch the shelf.  For the glaze firing, I wax that same circle and clean off any glaze that might end up there.  If you’ve already applied underglaze to that area, you can use one or more kiln stilts to support the bowl and keep it off of the shelf.  Hope this helps - good luck!

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It depends on the brand. Some you can without it sticking, some will pluck. Some colours within the same line will work better than others. Some colours will flash onto the shelf or surrounding pots. It’s a good idea to do a little test pot on a cookie or a waster before you commit to a bunch of them. Keep in mind most underglazes have a wide range of possible application times, so you can run the test before applying the underglaze to your main project. 
 

You should also bear in mind issues of long term durability when you’re talking about functional work, especially if you plan on selling it. Underglaze that isn’t covered and that is on a surface that will be subjected to a lot of abrasion may wear off over time. 

 

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