I get this question all the time so here are my FIRING GUIDELINES:
Let's assume for the moment that you are firing Reusche Tracing Black 57R001 or some other "High Fire" glass stainers color. You have applied this to a conservatively cut piece of glass of a thickness around 1/8". Your glass is not etched flashed glass, a piece with an extreme inside curve that you've taken a grinder or saw to achieve nor have you drilled any holes drilled through it. If you do have an atypical piece read the caution below*.
According to the Reusche catalogue your pigment fires between 1100F and 1400 F.
ELECTRIC KILN:
A general guideline would be to bring the kiln up slowly - for thin glass (1/8") in an electric kiln I recommend you take a minimum of 1 hour to reach 1000F after that you can climb quickly to the firing temperature then do a short hold. Going slowly on the way up is good for the glass and also kinder on the kiln. If your kiln is made of hard brick - heat it more gently, if it is all soft insulation you can go faster. Shut off the kiln when finished and let it cool on its own.
I am often disappointed by texture that I pick up on the back of soft glass. To reduce this I lower the firing temperature to 1135F - 1150F and hold at that temperature for 20-40 minutes. I would suggest this as a starting point. Up the temperature by 20-25 degrees if you find that the fired paint is not glossy enough. This will also depend on the kind of glass you have painted on as some glass is softer than others. Keep a kiln log and experiment until you know how your kiln fires. Use kiln wash, a bed of whiting or fiber paper as a separator on the shelf.
If you are using a repurposed ceramic kiln made of fire brick it will hold a lot of heat so it will not be necessary to do a ramped firing on the cooling end of the cycle. For 1/8" glass I don't do an annealing cycle in any of my kilns. If you start fusing or painting on glass thicker than 1/4" you will have to revisit this issue and add a ramped cycle up and down - but for now you should be ok.
You can crack the lid of the kiln 1" at 400F, 6" at 200F and open the lid all the way when the pyrometer reads 100F. It's safe to remove the glass when you can hold your hand on it. If you must push it - remove the whole shelf and cover the glass to protect it from drafts with a stack for newspapers - as long as they don't catch fire!
This is all pretty conservative and you may become bolder as you get some experience. I find that I get pretty bold in a workshop situation then I back off once something cracks! As always if you have put a lot of work into the piece - be more conservative.
HOAF GAS KILN:
Understand first my Hoaf is totally manual. After lighting the kiln I turn the gas regulator down to 40% and let it climb until it reaches 1000F before I turn it to full blast. I shoot for 1250F with no hold time. Turn it off and let the kiln cool on its own.
*CAUTION: When refiring glass that you may have pushed in the initial cooling or if you are firing one of the atypical cuts mentioned above - be even more conservative when reheating. You'll want to take 3 hours to reach 1000F on the ramp up in an electric kiln and then hold there for 20 mins. Once you've done that you can proceed as before. Unfortunately this scenario is not recommended (nor possible) in my manual HOAF gas kiln - if this is your situation just give it your best guess and err on the side of caution. Personally I fire these ticklish pieces in my electric kiln.
STAINS AND ENAMELS:
Fire as above to 1000F. For stains I fire to 1050F; for enamels 1125F - no hold in the Hoaf but I will give a 20 min hold in my electric kiln.
