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Hi,

I haven't been using a kiln for very long. I am beginning by making small cabochons for jewelry to go along with my lampworked beads. On some of them, particularly those with a clear layer on top, I am getting a line around the edge. It looks like someone took a magic marker and made a line around it close to the edge. What is causing this and how can I stop it? Thanks for any help you can give.

By some chance are you grinding your edges and are you using Thinfire?

I've had that combination bite me before.

Tony

Tony,

I am grinding my edges, but I do not use Thinfire.

Sharon

One possible cause is when the piece of clear glass you put on the top is not a slightly larger than the rest of the cabachon. When the clear glass top is not large enough to completely cover the cabachon, you get a mark on the edge.

This could be what you are seeing.

Alecia

artisand wrote:Tony,

I am grinding my edges, but I do not use Thinfire.

Sharon

Are you washing them really really well before you fire?

As soon as I finish grinding mine, I plop them in a bowl of warm water and leave them there until I am ready to wash them. This helps keep the ground glass from drying and sticking.

I wash them with dish washing liquid and rinse, rinse, rinse thoroughly. Then I dry them on a soft old towel.

Then they get fired. I rarely get any marks on the edges.

Geri

Thanks fcr the help. I'll try enlarging the top layer and washing it well. I thought I was doing both, but maybe I'm not as consistent as I should be.
I get these lines on a lot of my pieces. Thanks again.

Tony Smith wrote:By some chance are you grinding your edges and are you using Thinfire?

I've had that combination bite me before.

Tony

I had that happen to a whole batch last week. Thought maybe it was one of those virus things.

I ground, used superspray and thinfire. Left a haze around the edge. So I re ground and omitted superspray. Same thing. Is it the grinding, the thinfire, or the combo? I had never seen this before but I've not used much thinfire before either.

Jack

If I have to grind my cabs and fire them again I do put a little SuperSpray on the edges (insurance) but I fire them on my trusty 110-J covered with BE dry kilnwash.

Judy

Are you using dichroic or irridzed glass? If so you may be seeing some of the coating.

Barbara

What are superspray and thinfire and how are they used? Obviously they are not causing my problem! Today I was making very small earring cabs with clear dichro over black-backed dichro and they both balled up individually, and usually the clear top slid to the side. Any idea what I did wrong?

Thanks, Sharon

Jack Bowman wrote:

Tony Smith wrote:By some chance are you grinding your edges and are you using Thinfire?

I've had that combination bite me before.

Tony

I had that happen to a whole batch last week. Thought maybe it was one of those virus things.

I ground, used superspray and thinfire. Left a haze around the edge. So I re ground and omitted superspray. Same thing. Is it the grinding, the thinfire, or the combo? I had never seen this before but I've not used much thinfire before either.

Jack

There was discussion in the past about thinfire causing this, but I don't know if a definitive answer was arrived at. But I know it happens without using thinfire. I haven't found superspray to do anything to prevent it, nor borax. I first grind with a regular bit, then follow up with a fine bit, which helps some. I find it doesn't happen much if I am just firepolishing, and don't take the temperature too high, but at full fuse it is much more likely. Cleaning really well seems to be key to avoiding it. As Geri mentions, dropping the pieces in water immediately, then cleaning well later.

artisand wrote:What are superspray and thinfire and how are they used? Obviously they are not causing my problem! Today I was making very small earring cabs with clear dichro over black-backed dichro and they both balled up individually, and usually the clear top slid to the side. Any idea what I did wrong?

Thanks, Sharon

Sharon if you fire the two pieces of glass with the dichro sides facing each other then they can't stick to each other. Dichro won't fuse to dichro. I am guessing, if you are working with dichro that your metallic sheen may be due to the dichroic coating coming out on the sides. Lampworkers sometimes refer to it as dichro "scum".


Barbara

Barbara,

Thank you so much! That is exactly what I am doing. I was told to put the clear dichro face down so that it would be enclased by the clear on top. It is the ones with clear dichro over a black-backed dichro that I am having problems with. If I want to layer clear dichro, do I put the pattern side face up? Will it withstand the kiln heat. I know with my torch I can easily "burn-off" the dichro if it is face up.

I am trying a batch now with the top piece a substantially larger piece of clear glass to see if it gets rid of the dull line on the edges. Can I just not layer dichro's? I know I have seen it done.

Thanks again,
Sharon

Judy,
What is a trusty 110-J and how does superspray work? By covering with BE kiln-wash do you mean the shelf or covering the cab with dry powder?
Help!

You can find a true description of 110-J on the board. It can be ordered through Brad. Try online catalogue.

As for the dry BE -- just sprinkle it on the 110-J and it extends the life of the 110-J and gives your pieces a very smooth back.

Regarding the SuperSpray -- this subtance is 99% lead-free and prevents devitrification/scum buildup. I always use it on the edges of pieces which are cut with the saw and on ground edges.

Hope this helps.

Judy

Although I do love SuperSpray I would strong suggest you NOT use it on jewelry. A splash of Limeaway and certain other things will destroy the finish SuperSpray and turn it white.

I learned that the hard way after putting Limeaway on the back of a bowl to remove stuck kilnwash that had superspray on the front. Wherever it ran and touched the superspray, the surface turned white and ugly. You never know where someone will put their jewelry or what they'll be doing when they wear it.

LOL. Not long ago I had a customer call to ask me why a sterling silver ring she bought was tarnishing. I thought EVERYONE knew sterling tarnishes, especially when it's subjected to various household chemicals, even handcream. Apparently not...

Geri

Judy

Let see if I understand. If I use the 110J fiber paper and "Sprinkle" (to cover completely?) kiln wash on it I can fire on that instead of waiting for my kiln wash to dry? How many times before needing to replace it? So far I am just firing small pieces to 1500 degrees. I need to get another kiln shelf. I never seem to remember to recoat it the night before so I end up having to dry it in the kiln, which is another stiep, which makes it difficult to finish and be able to turn my kiln off before school is out and I make the kiddie run. Another shelf would solve my problem (if I remember to keep the extra one coated), but the fiber paper sounds like a great solution, too. Does the powdered kiln wash stick to the back surface of the piece? Thanks.

Sharon

artisand wrote:Barbara,

Thank you so much! That is exactly what I am doing. I was told to put the clear dichro face down so that it would be enclased by the clear on top. It is the ones with clear dichro over a black-backed dichro that I am having problems with. If I want to layer clear dichro, do I put the pattern side face up? Will it withstand the kiln heat. I know with my torch I can easily "burn-off" the dichro if it is face up.

I am trying a batch now with the top piece a substantially larger piece of clear glass to see if it gets rid of the dull line on the edges. Can I just not layer dichro's? I know I have seen it done.

Thanks again,
Sharon

Sharon, if you want to put the clear dichro dichro side down over a piece of black backed dichro, stick a little clear glass between them. Then all will stick when you fire the cabochon.

Regarding the coating creeping up, which is what I think is accounting for your "metallic" lines: A solution many people on this board have employed is to make their final layer clear glass and make it a bit larger than the rest of the glass so that it will cover those lines. Of course the lines will reappear if you do any cutting or grinding.

If these are cabs you make in just one firing, I recommend the following:
satrt with your black backed dichro, dichro side up. Top it with the clear backed dichro, dichro side up. Finish with a piece of thin clear glass that is a little larger than the other two pieces of glass. Fire, and voila, cabochon!

You can full fuse dichro dichro side up in the kiln, it won't burn off. The torch is much hotter than the 1500 degrees or so that you are firing at.

One more thing - about the spray. I am not too fond of sprays myself and usually employ the following tactics to reduce the possibility of grinder scum mucking ip the clarity of my edges. I soak the glass in water immediately after grinding, I scrub it with those green 3M scrubbie pads, and if the edges are rough I will "grind" them to a finer grit using diamond pads and elbow grease. Another thread recently mentioned where you could get the diamond pads.

If you search under "dichroic side down" or something like that on this board and in the archives you will probably find as many different suggested solutions as there are people on the board. These are just the way I do things.

Barbara

Barbara,


Thanks so much. You have been very helpful.I will try the various things you have suggested!

Sharon

Hi Judy,

I got the 110J and sprinkled it with kiln wash. I used a screen tea-ball but it still did not sprinkle completely smoothly. I was adding a layer under my cabs with a wooden pick to make a channel. Where the new piece of glass met the old, I have a gray line, especially on the white ones, although there is a dull line on the blacks, as well. I did forget to prefire the 110J (oops, got in a hurry!). I noticed when I peeked that the kiln wash turns a very dark gray during the firing, although it lightened again at the end of the firing. My cabs have a pebbly surface on the backs. Actually, I kind of like it. But I was wondering what I did wrong to get the gray line, and I'm sure at some point I will want something to have a smooth back. Do you add kiln wash after each firing? Thanks so much for your help. Thiis really seems like a great idea. The kiln wash was giving me fits. Takes forever to dry here. By the way, are you from Jax Beach? There was a photo of "Judy Schnabel" in our local paper and I know a Harry.

I also discovered that I prefer to add my backs (in order to make a channel for a chain) when I originally make a piece. I thought the originals would fire better without the possibility of sliding around. They did, but when I refired them, some of them became distorted. Live and learn! At least I will mess them up with the first firing and not waste more effort on them. TKS.

Sharon