Pottery Ceramics Glaze color drastically changed with decal fire

[JodRae]

Hello, I fired mugs with Mayco's Leather, and Smoke to cone 6. I used Coyote White Liner under the decal. After the first firing "pre-decal" the glaze turned out beautiful with browns, blues, and greens. I laser printed waterslide decals, and fired to 05 per the instructions. The decals did not adhere and all, I could scratch them away. Also all of the blues and greens disappeared from the glaze. I sent them through again to cone 03 which was recommended by a few other potters. This time the decals were perfect but the glaze is still colorless. Well I should say just an ugly brown now.  I am wondering if I send them back in to fire to cone 6 again will the blues and greens come back? Also what will happen to the decal? Any chance it will stay on?

Thank you!

Edited August 27, 2023 by JodRae

[Callie Beller Diesel]

Hi and welcome to the forum!

I can’t give you definitive answers to your questions, but I can give you some generalities to help you make your decision. There’s not really a guarantee though, and the Tl;dr is try it and find out. The worst case scenario is that you learn something that’ll make the next piece go easier. 

What you’re describing isn’t unheard of. Ideally a glaze used under a decal doesn’t change, but sometimes it does. Sometimes that change brings out good things, sometimes not. Looking at Mayco’s website photos of the glazes you mention, my guess is that the 2 are remelting a little and homogenizing at cone 03, but not melting enough to start doing all the fun things that make them look pretty. The hotter those glazes get, the more interesting the test tiles look. So it’s logical to assume that if you refire to cone 6, it could bring the colours back. (The usual warnings about running and possible cracking apply.) It might also just make more mud. It’s a 50/50 shot IMO. 

What will happen with the decal depends on the printer you used. If your  printing your decals with a toner printer, the decal will likely change in appearance as you go up in temperature. How much will depend on the iron concentration, but generally they’ll get more sepia toned. If the toner is one with a lower iron concentration, eventually get lighter as they sink into the glaze.. On a white glaze that doesn’t really flow much, I wouldn’t expect it to burn out entirely. If your glaze is more fluid, the decal  might be more inclined to fade, or details and lines may blur. 

However if you printed the decals with a printer that is specifically for ceramic decals, I’d expect the decal to at least partially, if not fully burn out. 

[neilestrick]

Many glazes will change color when refired at lower temps, especially those that have a lot of color variation. The only way to know for sure if  glaze will be affected is by trying it. A white or clear glaze is the safest way to go.

[JodRae]

Thank you both so much for taking the time to respond. I am going to re fire to cone 6 to see what happens. I am hoping the blue's and green's come back and I really hope the decals stays. I did print it with my home Black laser printer. I know it will turn sepia and I am fine with that. Not 100% sure of the iron content in the toner though. fingers crossed. I'll post an update for you.

[Callie Beller Diesel]

If you look on the MSDS sheet for the toner you’re using, it should mention an approximate level of iron oxide. I’m a bit rusty, but I think that the levels could range between 15 and 35%. The higher the concentration, the better the image will hold up.