ANNEALING UNKNOWN float GLASS

[Havi]

Happy Holidays, everybody,

I am using a float piece of glass.
I picked it up in the fields, near my home [there was an enormous pile of broken pieces of glass somebody threw away there].
The glass is 0.5" thick.
I only want to soften the edges [ instead of coldworking it], because it would create nice un-normal edges, yet not cutting. This should serve as a base to a glass piece of mine. And I like the result.
But I keep playing, hesitating, not REALLY knowing what I do - even if I write the details of the firing.

If I open the kiln while firing the glass looks unchanged, but when I take it out of the kiln, I realise the edges softened but not enough.

I feel like blind - - -
I do not know at what temp. the glass will soften enough , but not change its shape,
and I do not know how to anneal it.

Additionally I worry about devit...
It seems that this is strengthened glass [ I remember you used a particular adjective, but do not remember the word]

I read at Graham Stone that annealing temp of float is 555 C. [ 1031F]

One of my qestions is - is it safe enough to go down in temprature without staying at a certain point - for annealing? Just allow the kiln [paragon, old one but works great], to go down on its own pace?

I do the softening at 1400F.

Hopefully I have been clear enough to get more enlightening remarks from you


many thanks
Havi

[Tom Fuhrman]

I would think you shoud be OK letting it cool down on it's own since there is no combining of other glass and no tricky shapes you're making. when they produce float glass it can go from furnace(2100 degrees) to being put in a crate in less than an hour and if you're not doing any grinding or polishing on it, you could probably cool very rapidly and then it would be tempered. but it must be cooled consistently throughout.
TEST! TEST!

[Bert Weiss]

Try firing the glass to 1480ºF with a 10 minute soak. I have an unconventional way to anneal float glass. This works:
1000ºF hold for 2 hours
1000 > 900ºF take 2 hours
900 > 700 take 1.5 hours
700 > 300 take 1.5 hours

Note my strategy vs Stone is to hold longer at a lower temp then take the same time to drop 100º. Typically, Stone and I spend about the same time, only we do so at slightly different temperatures.

Always fire tin side down, and clean really well.