View Single Post
  #21  
Old 2013-11-20, 6:58pm
glassmaker's Avatar
glassmaker glassmaker is offline
Lizard rescue squad
 
Join Date: Apr 02, 2007
Location: Atlanta, GA
Posts: 1,126
Default

Quote:
Originally Posted by Genea View Post
Hmmm very interesting. I just heard from Evelyn Duberry that yellows and oranges tend to cool more quickly. News to me! I have been lampworking for almost 11 years and that is the first time I have heard that! Lol always learning something new Hmm my guess is that yellow apricot and sunburst are of the same family. I make it a game to figure out what batches they used to get what new colors This would totally make sense. I have heard they have been having trouble getting yellow apricot to turn out lately. I have mostly used my yellow apricot for smaller beads so I never noticed any problems. Thanks so much for your info
I definitely do not mean to disparage anyone, and hope everyone understands that. With that said, my suggestion would be to not believe everything you hear in the glass world. In this case, specifically the "news" you received regarding quicker cooling. There is a good reason you've never heard this before - it isn't true. Opaque cadmium-selenium colors (i.e., the range of yellow/orange/red) have some specific reasons they are more susceptible to cracking than other colors. Losing heat faster than other glasses is not one of them.

Without getting into a long explanation of glass chemistry, the short version is that the COE of Cd-Se glasses can change when they are worked for a long time. The more trips up and down in temperature, or the longer they are held at a high temperature, the more likely their compatibility will change. Generally speaking, they also tend to have a somewhat higher annealing temperature than most other colors. I doubt these are the only reasons you had cracking problems with your beads, but I certainly think it is/was part of the issue.

Also, regarding the use of sodium bicarbonate to change the texture on the surface of the bead. Sodium is a strong flux that increases the COE and lowers the viscosity of glass. So doing this changes the COE of the surface glass and introduces extra stress into your bead, making it more likely to crack. I'm not saying you should never use this technique, just be aware of the issues it can cause if you do. The flip side of this coin is that the bubbly surface created can help absorb the extra stress introduced into the glass by the change in COE. But you still need to be careful.

Brad

P.S. I tried very hard not to comment on this so as not to offend anyone, and I very much hope I didn't. But there is so much hearsay based misinformation floating around the studio glass world that I finally concluded that not commenting on this would have been more of a disservice than anything.
__________________

To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.

Last edited by glassmaker; 2013-11-20 at 7:02pm.
Reply With Quote