fire polish vs slump
- March 24, 2016 at 5:21 pm #10327MothsgalParticipant
As I’m learning to work with glass, I’m finding lot’s of information out there. I’m a jump in and just give it a try kind of gal. I like experimenting with the glass to see what it does and how it behaves. My pieces are textured, usually fused to a soft fuse, or a combination of full fuse then soft fuse. While trying to solve my devit problem and cold working to get all sides of my pieces glossy I ran across a solution from Glass Campus that talked about fire polishing a piece quickly (ramping up slow and cooling slow to prevent thermal shock) which polishes the glass but happens too fast to sag or distort. I’m wondering if any of you have any input about this….the information on this forum is fantastic!
This is what they say: Segment 1-ramp 400F to 1000F hold 20 min. Segment 20 ramp 1200F to 1200F hold 4 min. Segment 3- ramp full to 960F hold for 60 min. and finally Segment 4 ramp 400F to 300 F. “The 20 minute hold in Segment 1 is to ensure the glass is a uniform 1000F temp. This is important because glass won’t thermal shock crack above that temp no matter how fast the temp changes. The 1200 degree per hour ramp in Segment 2 takes the temp up too fast for gravity to have any significant effect on the glass. The 4 minute hold is just enough to fire polish all surfaces but not long enough for gravity to do anything destructive”.
I guess my question is: would this work for pieces that are already slumped but I want to have the bottom or back side glossy along with the front/inside or would the pieces deform? Cold working doesn’t seem feasable considering the texture. I would probably sandblast the pieces first to get a nice uniform finish that can polish. I did try glass etching cream which worked spectacularly on a piece that had a lot of devit. I’m imagining a bowl or vase where both inside and outside are equally important in the design. I’m going to do a test on something simple that I can risk, but thought I’d get your imput first.
Thanks so much!
KathyMarch 27, 2016 at 12:03 am #13598gypsycolleenParticipant
I’d like to know too! I’m making glass beads with handmade molds, and the top side is the only side that is smooth.March 30, 2016 at 6:37 am #13599Stephen RichardParticipant
The infgormation in this quote needs to be treated with care:
“The 20 minute hold in Segment 1 is to ensure the glass is a uniform 1000F temp. This is important because glass won’t thermal shock crack above that temp no matter how fast the temp changes. The 1200 degree per hour ramp in Segment 2 takes the temp up too fast for gravity to have any significant effect on the glass. The 4 minute hold is just enough to fire polish all surfaces but not long enough for gravity to do anything destructive”.
Yes, it is important to have the glass at the same temperature throughout before any rapid advance in temperature. However the temperture given is not a universally applicable one. It depends on the glass you are using. For some Bullseye and Uroboros glass 537C is their annealing point. So you need to be about 110F above that to ensure the glass will not thermal shock. For float you need to be at about 605C for your soak.
If the piece is already shaped, you need to do this in the mould. This is hard on your mould, think about the firing requirements for your mould. Also think about the physical nature of the effect of heat on glass. Your slump termperature is below the fire polish temperatue, so it will deform. This suggested techniques works only on flat pieces. The schedule on 6mm pieces. It needs to be adjusted for thicker pieces.
Dennis Brady often pushes techniques working at the edge of technical possibilities onto novice fusers. Be careful.
Stephen RichardMarch 30, 2016 at 9:08 pm #13600MothsgalParticipant
Thank you, Richard. I was skeptical and didn’t want to experiment until I got some feedback. You have great information!
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