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Boro Room -- For Boro-related tips, techniques, and questions.

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  #1  
Old 2017-04-02, 6:45pm
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Default What temp can I open the kiln?

Usually I run the kiln overnight and take stuff out in the morning, but to get enough pieces made in my little Arrow Smith kiln for my daughter's wedding, I may need to do two loads a day. Is it 750, 800 or 850 that I can open the kiln? Some pieces are 1" in diameter spheres, others are 11mm rod.

I really need a bigger kiln.
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Old 2017-04-03, 8:15am
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Default Cooling Rate

The best would be to shoot for 500. You may slightly vent the kiln sooner but be cautious. Remember the inner parts are always hotter than the outer area.
So when they contract during the cooling process, they can put tremendous strain on the surface area, if it has cooled to much. The piece may come out of the oven and look just fine, only to crack later on due to a change in room temperature or altitude (air pressure). The Mt. Palomar telescope lens was annealed for 18 months. That was the second lens, the first was lost due to cooling to rapidly. Technically the glass should be held at the annealing point 10 mins per millimeter thickness, then brought down slowly. Boro can endure more torture than soft glass and quartz glasses would hardly notice it at all. With a devise called a polariscope you can see the stress in the glass.
I hope I haven't ruined somebody's wedding here. But, oh well, next time start sooner.

Have fun , Wayne

P.S. 1 inch equals 25.4 millimeters if they are solid spheres if not go by the wall thickness.

Last edited by hyperT; 2017-04-03 at 8:21am.
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  #3  
Old 2017-04-03, 11:15am
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Default

I don't do boro at all but with my soft glass I wait until it gets down to 200 and even then I might just transfer stuff from the kiln to some kaolin wool blankets.

They have them or something like them in the hardware store that the plumber puts behind the copper pipes they want to solder together to keep from setting the house on fire.

Only my two cents and worth every penny you paid for it.
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Old 2017-04-03, 8:37pm
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Ok, I'll shoot for 500. I think I can still get 2 loads a day if I do the thinner pieces first thing in the morning. I'll just plan to do the thicker spheres separately so they can have a longer soak and gradual decrease like I do with marbles. The wedding is a few months away so I should be alright as long as I keep at it.

Phil, you are more conservative on soft glass than me. I always figure 300 as safe, although usually stuff stays in the kiln overnight till room temperature.
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Old 2017-04-04, 5:32am
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Default 500

I did mean to vent the kiln at 500 not open it all the way.
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Old 2017-04-04, 7:50am
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I may be conservative but I don't take any boro out until it's below 200 degrees and not even then for marbles...I've watched it crack. Just because it can take the stress doesn't mean it's not in there.
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Old 2017-04-04, 9:14am
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Default Exactly

Quote:
Originally Posted by dragonart glass View Post
I may be conservative but I don't take any boro out until it's below 200 degrees and not even then for marbles...I've watched it crack. Just because it can take the stress doesn't mean it's not in there.
I always let it cool completely down before I open or vent the kiln at all.
Because I do have a polariscope. It is better to be safe than sorry and not get in a rush for any reason.
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  #8  
Old 2017-04-04, 6:53pm
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Good to know, thanks!
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