I embarked on a new test trying to figure out with smaller more angular molds if 3mm or 6mm thickness of fused glass made a difference in being able to get better definition of the mold. I used Bullseye’s Four-Square Dish (8935) for all of the following tests.
When I first started fusing glass, I slumped most of my glass pieces at 1225 degrees F based on information I had gleaned from various forums and tutorials. I started to have a problem with larger plates developing a large bump in the center of the base and as I was in a class at the time, I asked for advice from other more experiences fusers. I was told that I was taking my slumping schedule too hot and I should not go over 1180 degrees F. So I have been using 1180 degrees F for my top temperature in my slumping schedule and it works quite well for my kilns and my pieces.
I recently bought some new molds which have more angular indentations, and my pieces did not seem to be taking advantage of the angles. At first I assumed this was just the way it was, but then when I was in the Bullseye Resource Center, their fused pieces showed off these indentations quite nicely. I noticed that in many of the smaller, angular molds, they had only used a single sheet of 3mm glass and so wondered if this was the key.
Hence my desires to do some testing. Spoiler alert: I have to admit that for each test, I ended up with more questions and additional new things to try, so this post is just the beginning of answering the question.
I first made a 6mm base of cyan and deep red glasses. I read again many posts and it seems that many people slump deeper molds around 1220-1225 degrees F, so I decided to start with 1225 degrees F for this dish holding it for 10 minutes. The dish came out nicely, but the sides are softer and not what I was trying to accomplish.
Four-Square Fused Glass Dish in Cyan and Deep Red (6mm thick)
My second plate was a single sheet of 3mm glass and again I slumped it using the same temperature of 1225 degrees F for 10 minutes. I had really expected to see a difference in the indentations of the mold between the 3mm piece and the 6mm piece and I did not.
Four-Square Fused Glass Dish using 3mm Bullseye Special Glass with Extras
As I was in a hurry for my 3rd piece, I just used a 3mm sheet of clear glass this time taking the kiln both hotter to 1250 degrees F and holding it for 15 minutes. This time I did indeed end up with more defined indentations. But I realized after the fact that my first two pieces were opaque and the clear was not and hence perhaps since I altered the viscosity of the glass, this was another variable to which I needed to test.
Four-Square Fused Glass Dish in 3mm Clear Glass (and taken to hotter slump temperature)
Here are all the factors which I believe are important and could possibly alter the end result:
1) thickness of the glass
2) viscosity of the glass
3) maximum slumping temperature
4) hold time at the maximum slumping temperature
My next tests this coming week will be to do a similar opaque 3mm sheet to test 2 but at the higher temperature and then also to try a 6mm fused blank at the higher temperature of test 3 to see if the opaqueness/viscosity play into the end result.
Of course, all the pieces are visually nice and completely functional for nuts, dips, salt tastings, and so forth. But sometimes you just have to know How Things Work!
If you have any suggestions as you have already discovered the secrets to doing this, please add your comments! This will help both me and any readers. Thanks. :-)