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Hi, I’m totally new to bottle slumping & I was wondering what I am doing wrong that my painted Coca Cola labels burn completely off of the back, while the red burns off of the front leaving only the white. Meanwhile, my painted Corona labels stay on in the front but the back labels burn into my mold. Does anyone have any tips on a firing schedule that works to keep the paint on & save my molds? Or is theresomething I can coat the labels with? Thanks!

Many bottles use a paint that doesn't behave well in the kiln. Reds are especially problematical.

If you give us the schedule you used we may be able to make some suggestions, but my guess is that changing the schedule won't do much -- it's just the nature of the paint used on the bottles themselves.

I’ve been using:
1-500°,1100°,10
2-250°,1300°, 5
3-300°,1425°, 5
4-full, 950°, 40

That schedule looks pretty much ok to me, except I would anneal bottles at 1000, not 950.

About the only thing I can think of for you to try would be to see if you can get the slump at a slightly lower top temperature. That might help with the paint burning off, but my guess is that the paint is going to burn off anyway.

Thanks for your input! Just curious, why 1,000 instead of 950?
Also, sometimes I peek in (I can’t see much, it’s a tiny window) & my bottle has already slumped before step 3,,, so maybe I do need a lower temp in 1/2

cookies4b wrote:Thanks for your input! Just curious, why 1,000 instead of 950?

Because different glasses have different annealing temperatures. 950 is ok for art glasses like Bullseye and Spectrum, but 1000 is best for window and bottle glass.

Also, sometimes I peek in (I can’t see much, it’s a tiny window) & my bottle has already slumped before step 3,,, so maybe I do need a lower temp in 1/2

It the bottle has already slumped, you can just skip to the next step and start cooling down to your annealing temperature. So a lower temp would do the same thing.

Thank You So Much! I’ll try a new schedule & see what happens!

cookies4b wrote:I’ve been using:
1-500°,1100°,10
2-250°,1300°, 5
3-300°,1425°, 5
4-full, 950°, 40

I found a basic bottle slump somewhere on the web that was similar to this.

1-500°,1100°,10
2-250°,1300°, 20
3-full,1475°, 5
4-full, 1000°, 60

It's worked well for my needs (stick a wire into the neck before firing, fire, hang as a gigantic wind chime element. I've used this profile for everything from small olive bottles up to 1/2 gallon milk bottles. Sometimes glass patterns and/or labels remain visible, sometimes not. The bottom usually falls over onto the bottle side and is a bit of a bump at the bottom. Since I'm not going for anything artistic, none of these are problems. I don't remove labels and just allow them to fully or partially burn off; sometimes they melt into the glass which can be interesting.

The modern Coke and Corona bottles have, what I assume, are organic paints for their reds and other colors. The old Coke bottles, the red remains (I slump around 1325 Fahrenheit).