Devitrification and slumped bottles...

[Ness]

Please can you help me to help a friend in need?

She has been slumping champagne bottles and they always end up with some devitrification.  She has them squeaky clean and new kiln paper/kiln wash stuff, is it a temperature issue?

Can you tell me the secret to getting them right, please?

Thanks very much 

[Zeldazog]

Ness, can you get the firing schedule?  I must admit I don't know a lot about slumping bottles, the problem is going slow enough to allow air out, but that can mean too slow and too long in the devitrification zone

I did a Bailey's bottle the other week, and got the same problem (I also didn't go quite hot enough either, tis a bit bumpy!  But whole main body has devitrified.  Some glass is simply more prone to it.

Hope someone else can come up with better help soon!

[Ness]

Thanks Dawn, I'll get the firing schedule she's using.

[Sarah999]

Hi, I have done quite alot of bottles, and use this...

Rate       Temp        Hold
350        1000F       10 min
450        1300F       60 min - This is the bubbles squeeze.
9999      1510F       10 min
9999      1000F       30 min
350        450F        0 min

I havent had any problems with vitrification, so maybe this is worth a try? Unless this is the one she is using already.

Hope this helps

[Sarah999]

I forgot to say, If you are doing a bottle with a pattern on and you want to keep it. Soak at 1300F and then flash vent it to 1000F. I have never tried it as I have a top heating kiln and it can cause damage to it. So be weary!

[Ness]

Thank you very much, Sarah - I'll let her know!

[Nevthedigger]

A few years ago I tried experimenting doing the same thing with aqua glass Victorian ink bottles, and while some did turn an unattractive matt finish, some were nice and glossy. They were fired together, which told me that the glass composition did have a say in the final result, or the method which would be needed.