Trouble enamel firing in a kiln

Hi all, I hope someone can help me. I’m fairly new to enameling but have been quite successful firing using a torch (although I couldn’t seem to get counter enameling to work!). I’ve now bought a small kiln but I’m having a lot of trouble firing enamel using it.

When I fire in the kiln the piece comes out with black dots on it - basically bits where the enamel has not stuck and you can see the fire stained enamel beneath. I assumed that I must be over or under firing so did fairly extensive tests from checking it every 30 seconds to leaving it for 10 minutes. I’ve tried the kiln at between 780 and 820 degrees C. I found that the black spots were appearing even before the enamel got to the grainy stage and that they stayed even if I over fired to the stage where the piece went black at the edges and the enamel shrunk away from the edge. I tried a second coat on some pieces but even then the black indentations stayed. Having tried half of a batch various ways in the kiln I then tried firing a few of the same batch using the torch, to check whether it was something I’d done wrong before firing. They all fired just fine using the torch.

For info, I cleaned all the copper blanks using a copper cleaner called HG copper shine shampoo and rinsed well before drying and spraying with WG Ball Cellular Adhesive (which they describe as an alternative to Gum Tragacanth) and then sifting on a thin but complete layer of WG Ball white opaque enamel. I’ve tried various thickness of enamel powder but the results are the same - it works ok with a torch but not in the kiln. The kiln is a Prometheus Pro 7 and I’m firing on tripods on top of metal mesh on a kiln shelf.

Please can someone tell me what I’m missing? I assume in doing something basic wrong! Any help very much appreciated.

Thank you so much.

I have never used that brand only ever use Thomson, and my technique is clearly much more agricultural than yours ( I only use a torch ) are you using a fine sieve to get consistent size in the grain
being fastidious about not allowing foreign matter into the powder, When I clean my metal I just use fine emery cloth 5000 grit and the clean with metho and make sure not to touch after.
If I were to guess and I am no expert with enameling I would say foreign material is falling on the surface or is in the powder, is the kiln clean inside no particles that can be flying about.

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Originally Posted by china

I have never used that brand only ever use Thomson, and my technique is clearly much more agricultural than yours ( I only use a torch ) are you using a fine sieve to get consistent size in the grain
being fastidious about not allowing foreign matter into the powder, When I clean my metal I just use fine emery cloth 5000 grit and the clean with metho and make sure not to touch after.
If I were to guess and I am no expert with enameling I would say foreign material is falling on the surface or is in the powder, is the kiln clean inside no particles that can be flying about.

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Thanks China,

Yes, using a fine sieve as recommended. I don’t think there’s any way anything could have got into the enamel. The kiln is new and I’ve fired at top heat as recommended to burn off anything nasty. So not sure what to think! Will try a different cleaning method, but odd that it would work well enough for torch firing but not for the kiln...

Kate, when your kiln is completely coll run your hand over the inside and see if any thing is flaking off , I am taking a stab in the dark here as it seems as though what ever it is is coming from the kiln as it turns out fine with a torch

I use a kiln. It does sound like dirt.
I don't use any glues etc. I scrub the copper with a green scrubby and water. Dry with a clean cloth.
If you don't see any dirt inside your kiln and you are having the same issue with a few different enamels, try sieving on slightly more than you use for torch firing. It could be that the layer is slightly too thin.