Clear capping - WarmGlass.com

Clear capping

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Kaye
Posts: 15
Joined: Mon Jul 14, 2003 5:33 pm
Location: Camano Island, WA

Clear capping

Postby Kaye » Tue Jan 20, 2004 4:01 pm

This relative newbie has done a fair amount of fusing and a little bit of slumping but I'm only now getting ready to try doing both to the same piece. I want to try fusing some dichro designs on black and then slumping into a plate or shallow bowl (maybe 10-12" diameter). I'm assuming I ought to clear cap the piece before slumping.

If this plan is OK, should I even consider using a thin glass for capping or is two full thicknesses the only way to go?

Kaye

Cynthia

Re: Clear capping

Postby Cynthia » Tue Jan 20, 2004 6:57 pm

Kaye wrote:This relative newbie has done a fair amount of fusing and a little bit of slumping but I'm only now getting ready to try doing both to the same piece. I want to try fusing some dichro designs on black and then slumping into a plate or shallow bowl (maybe 10-12" diameter). I'm assuming I ought to clear cap the piece before slumping.


Not necessarily. Depends on what look you are shooting for.


If this plan is OK, should I even consider using a thin glass for capping or is two full thicknesses the only way to go?

Kaye


You can use a thin rolled glass to cap with and that way you aren't adding much additional thickness to the overall piece...but to fully fuse your piece successfully, you will need to have a solid two layers of thickness across the entire piece anyway (Volume control). If you are only tack fusing your dichroic elements to a single layer of black...then capping could present some real difficulties.

Kaye
Posts: 15
Joined: Mon Jul 14, 2003 5:33 pm
Location: Camano Island, WA

Postby Kaye » Tue Jan 20, 2004 7:09 pm

If you are only tack fusing your dichroic elements to a single layer of black...then capping could present some real difficulties."

Can you elaborate on this? What difficulties? Could I full-fuse it and then cap? I was planning to use black-backed dichro so thought the coating should be protected from wear and tear.

Kaye[/quote]

Cynthia

Postby Cynthia » Tue Jan 20, 2004 9:04 pm

If you take a single layer of 3mm thick glass and take it to a full fuse, the glass will contract or pull in together in an attempt to achieve a volume of 6mm in thickness. If you layer up a piece that is 9mm thick, it will spread to thin down to 6mm unless you dam it up. This is what volume control is about. If you try to full fuse occasional bits of dichroic glass onto a single thickness of 3mm glass, your base glass will contract to thicken unless you have an even 6mm of glass across the entire surface.

You can successfully tack fuse small elements onto a base piece of glass that is only 3mm thick with regard to volume control because at tack fuse temps the glass isn't yet viscous enough to move much.

So to full fuse without any distortion to your size and shape, you need two full thicknesses of 3mm thick glass layerd upon each other. Then you will get a smooth and flat surface in which you could clear cap.

If you tack fuse and leave a lot of relief on your piece, then attempt to fire on a clear cap, you will trap air between the cap and the base piece. The cap of glass will laminate along the edges before any leveling out of the glass can happen... leaving bubbles of trapped air that give (when unintended) a poor appearance and a lumpy surface.

Do some testing to illustrate for yourself what volume control is.

Cut some 2" square pieces of glass. Make one stack on your kiln shelf with two thicknesses of glass, then stack one that is three pieces of glass thick and finally, put one single thickness piece down on the shelf to be fired. Full fuse them to 1500F and see what you get. Finally, cut a base piece of glass that is 2" square. layer up some bits of random glass, then place a clear cap on it. Fire this one with the other test stacks too. You'll see what it's all about much better than I can explain it.

Kaye
Posts: 15
Joined: Mon Jul 14, 2003 5:33 pm
Location: Camano Island, WA

Postby Kaye » Tue Jan 20, 2004 11:43 pm

Many thanks, Cynthia! I've made lots of cabochons with dichro and clear capping (in my Quickfire), but in that case volume control isn't very important. I've only recently gotten a bigger kiln and so far I've fused a lot of Christmas ornaments and two-layer coasters--and done a few single layer slumps. If I understand what you're saying, I should fuse two thicknesses of black under my dichro and then I could clear cap, yes?

Cynthia

Postby Cynthia » Wed Jan 21, 2004 1:21 am

Yes. :wink:

Brock
Posts: 1519
Joined: Mon Mar 10, 2003 1:32 pm
Location: Vancouver, B.C.

Re: Clear capping

Postby Brock » Wed Jan 21, 2004 3:10 pm

Cynthia wrote:
Kaye wrote:This relative newbie has done a fair amount of fusing and a little bit of slumping but I'm only now getting ready to try doing both to the same piece. I want to try fusing some dichro designs on black and then slumping into a plate or shallow bowl (maybe 10-12" diameter). I'm assuming I ought to clear cap the piece before slumping.


Not necessarily. Depends on what look you are shooting for.


If this plan is OK, should I even consider using a thin glass for capping or is two full thicknesses the only way to go?

Kaye


You can use a thin rolled glass to cap with and that way you aren't adding much additional thickness to the overall piece...but to fully fuse your piece successfully, you will need to have a solid two layers of thickness across the entire piece anyway (Volume control). If you are only tack fusing your dichroic elements to a single layer of black...then capping could present some real difficulties.


Very good explanation Cynthia. Crone the stows! Brock
My memory is so good, I can't remember the last time I forgot something . . .

Vickie
Posts: 35
Joined: Thu Apr 03, 2003 7:57 pm

mm vs inches

Postby Vickie » Fri Jan 23, 2004 11:31 pm

Can we please explain things in inches instead of mm. I think I could understand the math better.
Thanks,
"Not a mm person"

Brad Walker
Site Admin
Posts: 1380
Joined: Fri Mar 07, 2003 9:33 pm
Location: North Carolina, USA
Contact:

Re: mm vs inches

Postby Brad Walker » Sat Jan 24, 2004 12:14 am

Vickie wrote:Can we please explain things in inches instead of mm. I think I could understand the math better.


3mm = about 1/8" = one layer of standard thickness glass
6mm = about 1/4" = two layers of standard thickness glass

thin glass is 1/2 the thickness of standard thickness glass.

Roni L.
Posts: 1
Joined: Sat Apr 05, 2003 9:06 pm
Location: ARIZONA
Contact:

Thank You Cynthia

Postby Roni L. » Sun Jan 25, 2004 12:17 am

Cynthia,
I am one of those "newbies", I want to thank you for the explanation using 2 layers of base glass it was excellent. I also fuse pendants and just gave up on bubbles and a lumpy top layer. I can't wait to try the 2 layers on the bottom.
I read this forum almost every day all of you are very kind sharing your information. I have learned sooo very much.
Thank you again.
Ronihttp://www.tradewindgallery.com


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