Pot Melts

I have been messing around with pot melts occasionally but decided to try my Bullseye glass that has been sitting there for years untouched. This glass is tested compatible, i.e. when mixed with other colours and then cooled, the same cooling rates of all the glass will stop cracks developing. They are called pot melts because you use a terracotta flower pot to hold the glass and when the temperature of the kiln gets high enough, the glass melts and drips down onto a kiln shelf covered in fibre paper ( a refractory paper that stops the molten glass sticking to the ceramic kiln shelf).

6 centimetre pot filled with glass
I used all Bullseye glass as this is compatible with itself and will not cause stress fractures when cooling as all the different colours cool at the same rate.

Kiln set up
A quick shot of the inside of the kiln, excuse blurr.

Final cooled piece
Not bad, but I think a teacher would say, "Could do better". Much larger pot melts are turned into dishes etc but that is beyond my scope at present.

The Larger Melt
This melt looks a lot better. Its 23x22 cm. Again mostly yellow with touches of orange and green.


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kat's picture

Fried Egg

I think the final finished article looks a bit like a reversed fried egg or a yorkshire pudding! ;-)

It's interesting how, even though it doesn't look like you've put much red into the pot, it appears like there s a lot of red in the final melt. I wonder ifcertain colours are more dominant?

Did you purposely put the colours in that way initially or have you just been piling them in to the pot any-old way? I've a felling you're doing it purposefully but I thought I'd ask.....

Pat from Canvey's picture

Fried Egg

How dare you, just for that I shall screw up your front page again!

I've been experimenting really with how much of each colour will give the result I like and varying the way I stack the glass in the pot. In the second of these melts I used minute amounts of the accent colours and it gave a much more pleasing result. I have a larger melt in the kiln at the moment waiting for it to anneal before taking it out ( about 3 or 4 times the size weightwise of glass ). That's why I'm taking the before and after photos to remind myself how much of each colour I put in. The accent colour pieces I photograph on a 10x10 cm square of white paper so I can judge the size. The small melts are with a 10x10cm piece of glass and varying amounts of accent colours. I weigh and measure the resulting melt. I also put a note each time I fire the kiln of temperature,
time taken to reach soak temperature and how long a soak I allow. So you see there are many variables to play with before I come up with a sure fire method where I can predict the result.

 BJ's picture

Pot Melts

I don't know how you do it but each time I've tired the final result is cracked. I'm firing at 1000 dph from cold start to 1650 and holding for 60 minutes. Then I flash to 1500 and hold for 60 minutes. Then flash again to 960 and hold for 2.5 hours. From there I bring it down to 760 at the rate of 200/hr and hold for 30 then down to room temp. I know the first time I did it the glass stuck to the saucer I was melting into. I guess I didn't use enough kiln wash. the second time I tried kiln wash (6 layers), then thinfire cut to the shape of the saucer then a clear disk. This time it only broke in one place not like the other one that was in 100 pieces. So I'm still at a loss.... Would you mind sharing your firing schedule with me?

Pat from Canvey's picture

Melt schedules

I use a fairly old ceramic kiln with high, medium and low controls and a digital programmer that allows me to only set the final required temperature and whether to soak or not. I keep meticulous records of how long it takes to reach certain temperatures, 930 deg centigrade for a melt. Number each firing and use a new page for each firing, recording what happens whether the result is OK or excellent or total disaster.
I take it you are using glass with the same COE, all Bullseye Fusible or Spectrum Fusible for example.Sometimes you can use Spectrum Waterglass if you do the compatibility testing first.
I like to keep things simple so I know it takes about 4 hours for my kiln to heat up to 930deg cent. I soak for 2 hours at that temperature to give enough time for the glass to completely melt and run out of the pot. Then if i can't be bothered to flash vent, I just turn off the kiln and allow it to cool naturally. I try not to open the kiln door till the temperature is about 45 deg cent.

Green/blue spectrum border
Pot melt of mainly Spectrum clear waterglass with tiny pieces of accent colours

bj's picture

pot melt

Maybe that's my problem. I'm using glass with the same COE but I'm firing in a glass kiln. Maybe I need to come down on the heat since the heating source is from the lid of the kiln and the sides. I give it a shot and see what happens.

I've also been toying with the idea of dropping onto duraboard and not the kiln shelf. Have you ever tried to do that?

Anne's picture

Pot melts

Keep to the pepared kiln shelf. The thin fire wil become too hot. I use a glass kiln. What schedule are you using?

Pat from Canvey's picture


Your 1650 temperature, which I presume is fahrenheit, is equivalent to about 900 degree centigrade, but I am using 930 to melt my glass. Brad Walker's book "Contemporary Warm Glass" says that curved cracks through the middle of the piece are caused by improper annealing. What temperature are you opening the kiln at? I have had some cracks in the past where I became impatient to find out what pattern was in the melt and opened the kiln door too early, say about 80 deg. cent. As I liked the pattern in the piece, I kept it on the shelf, cut a border for it and covered the whole with clear fusible. The cracks healed themselves and the ghost of them hardly showed up in the final piece.
I haven't heard of duraboard. Presumably it is a thicker type of fibre paper or if not, does it require kilnwash just like the shelves. I have used fibre paper for some early melts but did not like the finish on the reverse of the melt so went back to Hotline shelf primer. Another good reason is that it is a lot cheaper than the fibre paper. I have tried boron nitride which is a lot more expensive, but I found that it gave no better finish than the hotline primer at high temperatures and still needed to be cleaned off the shelf after each melt.

Guest's picture


On Wednesday I took the melt that broke into 3 sections and refused it. I took it up slow and high on the temperature and found that my 3 sections came together but I can still see crack lines. I can't feel the line, but you can see the lines in the pattern of the glass. Even still it's very interesting! I'm totally captivated by it! I'll have to try another. I can see some very interesting possibilities here. Thanks for the tips!

As for fiber paper. Did you use Thin Fire or something thicker? With Thin Fire I would have thought that at that temperature the glass would be pushing the paper outward and not flowing on top of the paper. Interesting. I'm still a bit shy to drop directly onto my kiln shelf. Right now I'm dropping into a flower pot saucer coated with shelf primer. I feel safer with a controlled pour.

So thanks for the tips you've been most helpful : )

Pat from Canvey's picture

Crack lines

Yes you will still be able to see the crack lines unless you are able to polish the reverse side on a wet belt sander or a flat lap machine. Did you make a note of the weight of glass in your melt and the final size? That way, you will be able to drop directly onto the kiln shelf and not worry about the glass running over the edges. You could always put baffles around the edges if you are still worried. I used a thicker fibre paper in my initial melts but preferred the finish of the kilnwash shelf on the reverse. Finally, if you weigh the glass, you can get a consistent size of your melts and have a better understanding of how the patterns form if you also note how much of each colour of glass you use. Then you can experiment with different numbers of holes in the pots and see how this results in different patterns.