Painting & Firing Bought Vases
Posted 29 January 2008 - 03:39 AM
Posted 29 January 2008 - 10:45 AM
Hello, I think I can answer your question...the commercial vases are probably fine to fire. They are likely to be made from a stiffer glass than your friend's because they are made for production. the annealing temperature is something you will have to guess about, but I would guess it's around 950 degrees F. Look on-line for a conversion chart.
If you have a set of polarizing lenses, you can check the glass for stress before and after firing. Here is a firing schedule that I use when I'm teaching. Using moderately sized even-walled vessels. Put a piece of thick fiber paper under the vase to insulate it from the kiln shelf.
Ramp slowly (4 hours) to 850 degrees F (longer for large pieces)
Hold at 850 for 1/2 hour
Ramp to 1100 F (or firing temp for your degusa enamels)
Hold for 3 minutes
Crash kiln to Annealing temp (950 F or what ever you discover)
Hold at Annealing temp for 1 hour ( longer for large or thick to thin pieces)
Ramp slowly (6 hours) to 400 F
Let kiln cool on it's own until you can comfortably touch the glass. You can put a brick in the kiln to prop open when it's under 200 F. Actually sooner, but don't shock it with a cold breeze.
If you are going to be painting vessels, you will eventually want to invest in a controller for your kiln. But commercial glass is pretty forgiving, so you can probably eye-ball your pyrometer and use the low-med-high settings to approximate the schedule.
Posted 30 January 2008 - 04:49 AM
Thanks for replying!
I do have a controller on my kiln,but I just find it easier to take it up to temp then just end the programme as it seems to work fine on flat glass without an anneal. That's why this makes me nervous as I'm not used to it, and the glass isn't of even thickness so I'm glad to hear commerial glass is forgiving!
Will you be at the Festival of Glass at Stourbridge this year? I missed the masterclass you did in 2004.
Again, thanks for the help, I'll convert farenheit to degrees C and give it a go!
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