Annealing Lauscha Glass
This is my annealing schedule when I started mixing Lauscha with Moretti. I found this schedule from a post by Lenda Dewyer of lendabeads (excerpt follows) on WetCanvas. The only difference between us, is that I anneal Lauscha at 980.
Carol Anne Beckman - Annealing Schedule 2009
1. Ramp up as fast or as slow as you feel necessary to 980 degrees fahrenheit.
2. I do not have a separate temperature for soaking and annealing. I use 980 Degrees Fahrenheit for soaking and annealing.
3. Your program should be as long as your working time, plus a minimum of 2 hours. The 2 hour time must be increased if your beads are bigger than 4 centimeters. The guideline that I learned is 1/2 hour annealing time for each centimeter of bead size with a minimum of 2 hours.
4. So, a bead that had a largest measurement of 6 centimeters would need to be annealed for 3 hours.
5. After the annealing segment of your annealing program, you want to take the kiln down to 800 degrees Fahrenheit at a rate of between 60 degrees Fahrenheit to 100 degrees Fahrenheit per hour. The range from 60 degrees to 100 degrees per hour is in case you included a bunch of strange stuff in your bead and you want to baby your bead during this part of the annealing cycle...
6. Then, your hold time at 800 degrees Fahrenheit(step 5) is going to be the SAME as the amount of time you annealed your beads in step 3.
7. After holding, take your beads down to room temperature at a rate of 60 to 100 degrees fahrenheit per hour, depending again on how much strange stuff you mixed in with your bead. For more strange stuff, slower.
I hope that this helps you,
From Tanya Pertzoff-Wells: Personally, I think the ramping down is most important. I anneal a bit on the low side but have had very little problem with encased beads cracking so long as they are annealed (I had a lot of problems before I got the kiln!) I frequently encase with Lauscha clear over Effetre glass (when I encase with clear, I use Lauscha.) I’ve also encased with Lauscha over goldstone, metals, etc… with success. I try to make sure my beads AREN’T glowing when they go in the kiln since I am, as I mentioned, I'm paranoid about beads deforming in the kiln. I do flame anneal though for beads of any size before I put them in the kiln and I think that might make a difference. Who knows why one thing works for one and another for another…?
I think there must be almost as many annealing schedules as there are glass artists (not really, but there really are a lot of different opinions and most of these probably work just fine.) I work with a lot of Lauscha glass and have had no compatibility problems with Effetre glass, so I assume the COEs of the two are very close. Given that most of my beads are a combination of the two glasses, it would be difficult to use different schedules! I recently purchased Bandu Dunham's "Contemporary Lampworking" (an excellent book, although not as a first bead making book) which has an extensive chapter on annealing and useful tables for both borosilicate and Effetre glass. The schedules are different since the COEs, annealing temperatures, and strain points are quite different. The annealing temperature is a range, with thicker glass benefiting from a longer soak period at a lower temperature. Dunham recommends 15 minutes at a temperature of 968F for a 1 inch thick bead. I soak for 30 minutes at 950F for a bit longer since I think my kiln runs a little hot and am a bit paranoid about beads deforming under too high heat. The slow cool phase is the most important. I do know of several beadmakers who simply turn the kiln off at this point and have no problems. I don't since my kiln cools way too fast for this phase. For a 1 inch thick bead, the temperature change should be no more than 1.44 degrees F per minute or 86 degrees F per hour. I have been using 100 degrees per hour since almost everything I make is well less than 1 inch thick. Since Dunham's table recommends 107 degrees F for a .9" thick bead, I feel justified in this. This should continue until safely below the strain point - Dunham recommends a 40 degree F safety margin. So, the slow cool phase can end at 830F. I had been extending the slow cool phase down to 700F, but now end it at 800F (as I think my kiln runs a bit hot.) Dunham says it certainly won't hurt to extend the slow cool phase but is a waste of electricity. I have been able to cut 1 hour from my annealing schedule because of this information (and now that the summer months are here, an extra hour of sweltering.) After the slow cool phase is the fast cool phase. My kiln is well enough insulated that I can just turn it off at this point since the allowable temperature change for a 1 inch thick bead is around 5.5 degrees F per minute or 330 degrees F per hour.