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Decorating a vitrified porcelain tile


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Hi, is it ok to take a fired (vitrified) porcelain tile and decorated it with low fire glazes? A multi firing process, and I can get the glazes to stick with heat and spray starch... I want a decal that I made to blend into the tile, but a cone 6 glaze burns out the decal....so if I use the 03 glaze on the already fired cone 6 porcelain, will it work????

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It often does and is a practice you see in industry where tiles are fired to cone, the defects  removed and then glazed with lowfire glaze to finish. Stroke and coat glaze is popular for this but any lowfire glaze can be tried. China paint is fired much lower - cone 017’ish and simply adheres to the softening overglaze so that is another option available, same concept. The slang you may hear is multiple decorative firings and firing down. Each firing will stress the tile more so ya probably can’t do it more than a few firings and of course in the case of using lowfire glaze it needs to fit the COE of the original piece.

Generally a bit of testing to make sure everything works together as intended.

Edited by Bill Kielb
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That’s what I was thinking but not sure, Thankyou for the clear info. What is COE?  Also I don’t like the look of China paints ( they sit on top of glaze), that’s why I’m trying to glaze decorate and have the clear glaze open back up on refiring. I don’t know of any clear glaze you can use with very low temp China paints

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COE is coefficient of expansion. So when the glaze and claybody COE mismatch enough it usually leads to crazing or other glaze defects. Crazing appears as a spiderweb of cracks, it simply means the clay is expanding a bit faster than the glaze can. Shivering would be the opposite and glaze often pops off the pot as a result. Rather unnerving but two common forms of COE mismatch. Only way to know is by testing, there is no magic formula to tell what the actual fired COE will end up to be.

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Many years ago I did some experimenting with glazing factory tiles and porcelain dishes.    Low fire glazes did well on the tiles  but the low fire glazes had a problem on the dishes, it show up about a year after I did the test.  The glaze looked nice but starting popping off the dish.  I had the dishes placed around the room on a high shelf,  I was working away when I started hearing this pinging noise.   I looked up and it looked like pieces of glass flying through the air,  I got out of there.   When it stopped  I figured out it was glaze not glass from the dishes,  I cleaned up the mess and threw the dishes away.   Denice

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1 hour ago, Denice said:

Many years ago I did some experimenting with glazing factory tiles and porcelain dishes.    Low fire glazes did well on the tiles  but the low fire glazes had a problem on the dishes, it show up about a year after I did the test.  The glaze looked nice but starting popping off the dish.  I had the dishes placed around the room on a high shelf,  I was working away when I started hearing this pinging noise.   I looked up and it looked like pieces of glass flying through the air,  I got out of there.   When it stopped  I figured out it was glaze not glass from the dishes,  I cleaned up the mess and threw the dishes away.   Denice

Interesting... were the tiles those typical powder-pressed blanks or were they porcelain like the dishes? Very interesting 

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"Only way to know is by testing, there is no magic formula to tell what the actual fired COE will end up to be."

Aye that!

Glaze calculation software (e.g. GlazeMaster, DigitalFire, etc.) provides calculated COE values, however, as Bill points out, the numbers may not line up, especially when comparing very different glaze formulations.

However, calculated COE be very helpful, particularly when looking to adjust a formula to lower/raise COE. After four rounds of adjustment, the "low e" clear I'm using on white stoneware is performing well. It definitely helps to start with something that's close!

Edited by Hulk
exactly
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I do porcelain tiles now, using stencils and silkscreens, (the first 2 tiles below) but want to do detailed scenes using a decal of my work in monotone, then add color in another firing.The decal burns off sometimes and was thinking about the “firing down”‘process... looking for info really on how William De Morgan made his tiles???( 3rd pic of de Morgan. Tiles)

605BA2A2-D1CB-44D7-8B4D-FC497449393F.jpeg

5AF166A2-303B-454A-BACC-1F199B042947.jpeg

36FAB419-3738-43F3-BAEF-CB104D4A1F93.jpeg

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From this page  there is a link to someone who is doing reproductions of his work, their contact info here, I'ld send them an email and ask, worth a shot. 

One other thought I had was if your decals are burning out before the china paints are melted perhaps using a laser toner decal might be an option as they can take higher heat.

 

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