Uroboros - Help with Cracking issues

[GlassyEyedGirl]

189068

I recently got into a "Frit" phase, so I ordered some uroboros clear glass so I could use as much frit as I liked.... however, a large number of the beads and winestopper tops have been cracking. I have tried getting the glass really HOT before I put it in the kiln, but it doesn't seem to help much. I garage and anneal at 980 degrees.

Any advice would be appreciated! Thanks!!! :waving:

[imagesinglass]

Hi Beth,
What COE base glass are you using? If it's COE104 that's gonna be your problem. You have to use all COE 96 if you're going to encase in Uroboros. I can only see the crack in the bead on the left and it looks like thermal shock cuz it goes up the mandrel.
I think you may be garaging a little hot...I know everyone finds their own schedule but I garage at 920 and then ramp up to 960 and hold for 1 hour then ramp down at 100 degrees per minute to 700...the off to cool naturally.
Just my 2 cents...hope it helps.
Suzane

[GlassyEyedGirl]

Thanks Suzane! It is actually all 96. I got a little black and green to use for a base. But I only have had the cracking with the clear so far.

[squid]

Is the cracking parallel to the mandrel? It looks like it from the pics. If so, it may be that your kiln temp is off and you don't know it - mine was overtemp by 125 degrees, so I know it can happen.

[GlassyEyedGirl]

Thanks Squid. I will have to test it. How do I do that?

Wouldn't they just crack if it were too cool? Do they crack if it's too hot too?

[squid]

they could, depending on how fast you cool it. But it could very well be that your kiln says it is 980 and it is really 880 or whatever.

You will need a stand alone digital pyrometer to test it.

[beadgoodies]

You may want to consider switching encasing glass. Although Uroboros and the frit you're using are both 96 COE, frit has lead in it where Uroboros does not. Using leaded 96 COE encasement glass (like Reichenbach, Gaffer, or Kugler) might solve your problem.

[GlassyEyedGirl]

Beadgoodies, I was wondering about that! I don't have cracking problems with anything else besides Lauscha clear, and of course it is known to have its issues. I was kinda looking forward to using 96 for the specific reason that I figured it would have less cracking. I will try the leaded variety of clear. Thank you so much for the info!