Boron Nitride Spray is used for coating steel moulds in glass industry. There is no pre heating required. Here is experience of an actual user:
I use the **GE (Momentive) BN, and have been having much better luck with it as a slumping release than a casting release (which is what I wanted it for). I think there must be many different formulations out there, and that probably accounts for some of the variations in max temp.
What works best for me is multiple thin applications, prefired. That is, I spray a thin coat of GE BN across the piece as evenly as possible, fire it to about 1400, let it cool and rub it down gently to smooth it out. Then I respray and refire and--if I'm really paranoid, respray and refire again. Done that way, it releases very well at slumping temps, has fewer problems at higher temps and lasts through several firings if I'm careful. I doubt it would last 60 firings though--it has a tendency to flake off after about the fifth firing.
The big question for me is why that's better than kilnwash for slumping. For full fuse and casting, BN doesn't clog up fine detail in the mold and the finish is a little glossier with BN than with kilnwash...if your mold is a relatively smooth, even shape. If not, I'll probably be grinding the mold off the glass in a few places, and I'm getting so I can predict where that'll be...
I figure by the time I really figure it out I'll be at the end of the spray can, and I'll decide then if I really want to buy another can. I've also tried colloidal alumina in solution for a casting release as recommended by a refractory mfg...but so far that's not been very successful.
*GE Boron Nitride Spray is now Momentive Boron Nitride Spray II
I use the **GE (Momentive) BN, and have been having much better luck with it as a slumping release than a casting release (which is what I wanted it for). I think there must be many different formulations out there, and that probably accounts for some of the variations in max temp.
What works best for me is multiple thin applications, prefired. That is, I spray a thin coat of GE BN across the piece as evenly as possible, fire it to about 1400, let it cool and rub it down gently to smooth it out. Then I respray and refire and--if I'm really paranoid, respray and refire again. Done that way, it releases very well at slumping temps, has fewer problems at higher temps and lasts through several firings if I'm careful. I doubt it would last 60 firings though--it has a tendency to flake off after about the fifth firing.
The big question for me is why that's better than kilnwash for slumping. For full fuse and casting, BN doesn't clog up fine detail in the mold and the finish is a little glossier with BN than with kilnwash...if your mold is a relatively smooth, even shape. If not, I'll probably be grinding the mold off the glass in a few places, and I'm getting so I can predict where that'll be...
I figure by the time I really figure it out I'll be at the end of the spray can, and I'll decide then if I really want to buy another can. I've also tried colloidal alumina in solution for a casting release as recommended by a refractory mfg...but so far that's not been very successful.
*GE Boron Nitride Spray is now Momentive Boron Nitride Spray II
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