On the dangers of accepting advice on the internet as gospel...

[ps_bond]

I've just been playing silly buggers with my heat treating oven. A firing schedule I found somewhere for slumping bottles - which was very detailed - hasn't exactly given me the results I expected. I'm waiting for it to go through the annealing cycle, after which I expect to be able to retrieve a very, very flat Newcastle Brown bottle. I'll probably try the same program on a wine bottle; it's got more thermal mass, so might not get to such a co-operative flow temperature quite so quickly. Wonder what I'd be fishing out if I'd put a couple of bottles in?

Still, it's a salutary lesson (despite the obvious variables - differences in kiln responses for example); there's a certain amount of care and attention needs to be applied to advice read online.

Even mine

[bustagasket]

lol but yours is pretty darn good sir!

[mizgeorge]

Kiln working bottle glass can be a bit of a minefield though! I occasionally make beads using recycled glass, and have no idea what the COE of the glass actually is. I anneal them using the same schedule as for soft glass, and haven't lost any yet, but I'm never sure about selling anything made with them. I know each colour behaves very differently as well.

Bombay Sapphire looks especially gorgeous in bead form, or slumped though

Out of interest, what temperature did you take it up to?

[Lindyloo]

What on earth is a heat treating oven? This will come under the heading 'the thing I've learnt today'.

[ps_bond]

What on earth is a heat treating oven? This will come under the heading 'the thing I've learnt today'.

It's a kiln that was designed for heat-treating - hardening and tempering - metals, with a focus on steel. Mine is capable of hitting 1200C, with an 18" length firing chamber (and still runs on 13A single phase). It's got safety interlocks on the door which are making enamelling a bit trickier, but it is doable.

I went to 800C for 10 mins with this schedule; it looks very cautious both up and down. Some very slow ramp rates; took over 3 hours to get to the peak. Reading around a bit, it sounds as if other people's expectations of a slumped bottle is a cheeseboard whereas I'd expected a shallow tray. Some of the stronger colours are said to need a devit spray (not that I have any)?

All advice needs to be treated with common sense and caution - I remember someone who thought that quenching steel (in the hardening phase) in dry ice and acetone was a good idea. He was dissuaded before he tried it, thankfully - if that was being done, you'd do it *after* the steel was at room temperature, not plunging the red-hot metal into a volatile mix!

Wouldn't have done the steel much good either.

[mizgeorge]

The slow ramp rate's a good idea to stop cracking. From what I know about this (a lot of people I now do it) if you go to 700C and hold there for up to an hour before starting the ramp down this should give you more of a 'dish' shape. Alternatively, carve a kiln sheet to make a mould to slump into?

There seem to be a fair number of these around as clocks and cheeseboards at the moment.

[ps_bond]

I've got a tub of mouldable firebrick that might be interesting as a kiln mould. Texture can be a little coarse though.

It was seeing slumped bottles at Badminton that made me curious to try it - I'll probably run a couple more through for amusement; it's not core to what I'm trying to do, so it'll be playing rather than anything else.

Besides, if I go down that route it'll be pate de verre, glassblowing and anything else I can think of - I'm already having enough trouble resisting the lure of facetting as a diversion!