Hi. I just sent this message to Ask The Experts, but thought I would post it on the forum, also. Sorry if it is a duplicate....
I'm working on a project, trying to perfect the process to get a consistent outcome:
I start with a 1-1/4" length of 3/8" raw copper tubing. One end is crimped flat and a hole drilled through for a jump ring. I have slipped onto the other open end a copper end cap (such as would be used for plumbing, but not soldered - just held by tension). I then use the immersion technique of torch enameling (Mapp gas with a hothead torch) to coat the entire piece with several layers of enamel, to "seal" the piece. (Klyrfire is not used.) Sometimes it comes out well. Sometimes there are 1/8"-1/4" circles of enamel that ping off all the way down to the copper surface (usually from the bottom of the end cap), after cooling. Sometimes the surface chips off.
I have read various troubleshooting articles and experimented accordingly:
Copper dirty:I use a Pennybrite-type product copper clean, fine sandpaper, etc. I've tried not cleaning the copper at all. Sometimes it chips (even when clean), sometimes it doesn't chip (even when dirty).
No counter enamel: Can't do that in this case - it's a tube.
Mixed enamels: All my enamels are Thompson non-leaded medium fusing COE: 258-360 (cu) enamels. Sometimes I use transparent with opaque, it works at times, not at other times. Once I used only one color - Thompson op. 1010 undercoat, 4 layers - one chip popped off down to the copper.
Heating too fast, too slow, too hot, too cool: Not sure. Tried it all, haven't found what works consistently, yet.
After firing, I put the pieces into a heated pot of vermiculite and allow it to cool slowly. Sometimes chips, sometimes not. (Should I "anneal" the enamel in a kiln after torch firing?)
I've tried: two layers of clear flux, two layers of undercoat white, and two topcoats of transparent and/or opaque enamels. Sometimes it works, sometimes it chips off.
Is the copper tube and/or end cap expanding and contracting too much?
Not sure what to do at this point, so thought I would consult the experts!
Thank you for any help. Shirley in Oregon
Thank you for your reply, Candy. Yes, I have both of Barbara's books, but have read articles and watched other tutorials on the same technique. Just before I read your reply, I sent a message to Barbara through her website. I will check out the Inspired Enameling group on Facebook. Thanks for the suggestion.
Hi Shirley,
You have listed a lot of different things you have done with the enamels so its hard to differentiate where the problem lays but from what I read, if I am correct in what I am reading, you are applying 4 layers of enamel - if that is correct then the metal cannot handle so much enamel on the outside and none countered when the metal is cooling and moving under the enamel - Both the enamel and the metal expand and contract separately - so think oreo cookie - enamel on top and bottom - metal in the middle - it gives balance to the process of cooling - since you can't use counter the 4 layers of enamel on the tube are too much and the gauge of the metal may not be thick enough to handle all that enamel.
When you hear from Barbara, let me know her take on this.
Keep it working!
Trish
Hi, Trish. Thank you for your reply. Sorry for the confusing post - kind of how my mind works sometimes.
You are correct - I am using anywhere from 4 to 7 layers of enamel. The copper tube is appx. 22 ga, the end cap 18 ga. About 50% of the ones I've done turn out good. I also do a smaller size using 1/4" tube and endcaps, and those don't chip.
Barbara's comments were: 1. The copper isn't hot enough for the first layer of enamel; and 2. It's cooling too quickly and getting thermal shock.
So, that is what I'm going to focus on - being more attentive to my first fire (using 2030 medium fusing clear), making sure the copper gets hot enough - before and after the first layer of flux. And then when finished with subsequent layers, "flame annealing" it before placing it in a [hotter] vermiculite pot to cool very gradually. I will be doing this in a more controlled manner, keeping records of steps. I think the initial heat (or lack, thereof) is part of the culprit, since the smaller ones don't chip - they heat up quicker and hotter because of their smaller size. (I am coming to the conclusion that, eventually, I'll need to get a hotter (lampworking?) torch for the larger ones - but that's an entirely different subject!.) I will experiment, and then report back.
Also, Barbara didn't comment about the multiple layers. She made more reference to the issue of using utilitarian copper (intended for hardware and plumbing use) as enameling pieces, and the fact that the pieces are manufactured without enameling artists in mind. I think the main issue here is (and she mentioned it, also) to make sure the copper is really really clean, which is a little different from her traditional "no need to clean" philosophy for immersion enameling.
Thanks again for your reply and information. I'll keep you posted.
Shirley
I am using a kiln instead of a torch. Often when I work with copper tubes I first cover the upper half of the tube, use a horizontal support to hold it in the kiln Then fire. After cooling I clean the lower half and put the enamel on it and fire this half looking upwards. This is more work but no splitting off. I also use rather thin layers. Gabor
Thank you for your reply and suggestions, Charles. I usually don't have chips on the tube itself - the chips ping off of the end cap that slips over the tube. I wouldn't be able to counter enamel the inside of the end cap because it would no longer fit over the end of the tube. I could counter enamel the tube part, but not sure at what point I would do this in the process. I'll look into that. As far as applying the thinnest coat possible, I am using the torch-fired immersion process - heating the piece up to orange glow, immersing the hot piece into the 80-mesh enamel, then back to the torch. The amount of enamel that sticks to the hot piece is usually very scant, and I tap it to be sure there are no loose or thicker spots, then back into the flame it goes. I want the enamel to coat and seal the entire piece. The tubes are small - 3/8" by 1-1/4" long. The end cap is 7/16" wide by 3/8" long. I also do a smaller size using 1/4" tube - I don't have trouble with those chipping. I will experiment with fewer/thinner layers as you suggested. Thanks again for your input, I really appreciate it. Shirley
Hi, Gabor. Thank you for your reply and information. I am using a torch for this process, as well as the immersion technique to apply the enamel. The tube is crimped on one end with a hole drilled for a jumpring. There is an end cap slipped over the other end, held by tension. The entire piece is then enameled, all at once, in order to create a sealed chamber. It could be done in a kiln, I suppose. The piece would need to be suspended in the kiln by the hole in the crimped end. It would be rather labor intensive. I really want to make the torch process work, if possible. Thanks again for your help and suggestions, I will keep it in mind. I really appreciate all the feedback I am receiving. Shirley in Oregon