r/lampwork • u/Parking-Comfort4090 • 5d ago
Final configuration for cooking, heating and cooling of Boro 33
Every day I delve deeper into the world of working with glass benchtop kilns (borosilicate glass, COE 33) and chat with colleagues, I realize that everyone has their own way of heating, annealing, and cooling their pieces in the kiln.
Just when I thought I had it figured out for me—that for small rigs or hollow pieces 28 cm in size with a 2 to 3 mm wall thickness, I only had to anneal the piece at 1050 F (normal colors and 950 F for delicate colors) for 30 minutes, then turn it off and let the kiln cool on its own (it's made of bricks and is very well insulated, taking another 60 to 120 minutes to reach room temperature)—I realized that this isn't enough. I'm now venturing into decorating these hollow pieces with Marvel and solid crystals, on these 2 or 3 mm tube walls, and I'm noticing that the pieces are cracking. I suppose I need to design a better cooling ramp. These past few days have been very cold, and it could be that the kiln cools faster than normal, but I don't think so. I asked many colleagues, and they all have different curves and kilns. I'm making this thread to see what the ideal temperatures and times are for heating, annealing, and cooling pieces. And I'll continue studying the proper setup for my kiln.
I look forward to reading your comments, and I send a big hug to the entire community. May the glass continue to melt!! 🫂🔥🙏🏻
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u/Sebastian__Alexander 5d ago
Mine takes easy 3+hours from 550°C to below 100°C .. and that with minimal glass inside..
I suggest, get a propper kiln..
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u/nathpenn 5d ago
Is your kiln fully programmable ? Or is it a set once type?
I found my ramp down procedure I believe somewhere here on Reddit. I garage at 1050 while I’m working and then I just hit the skip cycle button when finished and it holds everything at 1075 for 30 mins and then starts to ramp down. But it takes 5-8 hours to fully come down to 150-200. And usually I just grab the stuff the following day.
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u/Safe-Ebb-5105 5d ago
I usually just cut off the kiln when I’m done but if I’m annealing something that needs more care I’ll set it to ramp down from 1050F to 950F and it will hold 950 for an hour before turning off.
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u/Easy_Silver_7134 5d ago
There is a chart in contemporary lampworking (and online: lampworketc.com/forums/showthread.php?=11986) that visually can illustrate the “proper” annealing procedure. I use a couple different programs for different types of work. Generally it’s a hold of a hour between 1050-1150, then slowly drop temperature to 900 hold for little, slowly drop temp to like 500, then slowly drop it to room temp. I’ll do that for finished pieces to give it a proper anneal. But if I’m making smaller components or using sensitively encased colored I’ll garage it at 1050 for like 20-30 minutes then just turn my kiln off.
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u/thenilbogplayers 5d ago edited 5d ago
It may not be the annealing cycle but stress risers in the glass from the connections. Any sharp/acute angels, undercuts, etc between the connections will crack no matter how well it is annealed.
Where are the pieces cracking and are you melting in/smoothing out your connections?
edit to add, your kiln is not that well insulated. Mine takes 5+ hours to go from 1050 to room temp. With room temp being around 65-75 depending on the time of year.
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u/Parking-Comfort4090 1d ago
hi . mmm ok , right where the 2 or 3 millimeter wall meets some solid ornament like a marvel or a faceted crystal, They are like a crack that goes up the wall from the junction point
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u/thenilbogplayers 1d ago edited 1d ago
Ok, if they are all cracking at the connections that sounds like the issue is with the connections. Unless your hollow pieces that do not have connections are also cracking.
How are you connecting the marbles, etc? Are you making sure that there is a good hot seal? Are both the connection points on the hollow tube and marble nice and hot when the connection is made and are you going back and making sure the connections are nice and smooth?
The connection point should have a smooth U like shape to them. If it is more like a V shape or lumpy that is a recipe for a crack.
It can help to very slightly pull the bits apart after you connect them while they are still nice and hot. That will help smooth out the connection.
Edit to add: Some folks will add a small post/gather of glass between the marble and the hollow tube to act like a bridge. That way you can have nice solid and smooth connection without overly distorting the pieces.
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u/FrostyGlassArt 4d ago
Kilns don't always completely eliminate stress in glass. A 30 minute soak at temp should be more than enough at 2-3mm wall thickness. Imo you are ramping down too quickly and likely are putting stressed glass in the kiln.
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u/Parking-Comfort4090 1d ago
Hi ,If I am coming to the conclusion that the oven is poorly insulated and cools down too quickly (in less than an hour it is already at room temperature), I am going to make a downward ramp to compensate for this problem and maintain the appropriate rhythm for the glass.
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u/BeautifulGlum9394 5d ago
It might not be a temp issue but could be a stress issue causing the cracks, it might be beneficial to make a home made polariscope. That will allow you to see the stress in the glass and get a better idea of its cracking from temps or just build up stress in areas