firing temps v length of prog

[shafeenan]

HELP! Thought I'd got to grips with my SC2 with fairly consistent result on single & double layers of glass with the following programme:
100C > temp: 400c   hold 2mins
   250C > 790c   hold 10mins
   down > 483c   hold 15m
   then off
I wanted to do something with 3 layers so thought I should go longer and followed the book's suggestions:
        200 up to 150C hold 12mins
    00 up to 315C  hold 12mins
   200 up to 515C hold 20mins
   315 up to 600C hold 60mins
   315 up to 760C hold 15mins
   crash 9999 to 537C hold 45mins
   37 down to 515C hold 60mins
   37 down to 378C hold 1min
   off
The result was a gloop!  The top temperature was lower than my tack fuse. So should I try the higher top temperature but not hold so long - or.....?
Advice, especially from anyone else with an SC2, would be so welcome (and yes, I do realise all kilns, even the same make will be different - but I am hoping that the principles are the same regardless!
Look forward to hearing from one of you oh so experienced fusers!  Have been calling my work 'pro-fusion' within the family, but I think 'con-fusion' would be more relevant!

[shafeenan]

OK - sorry folks. read my notes wrong and now checked on the kiln - my prog 1 was 730 not 790. So that sort of answers part of the question!
However, I'd still be so grateful for advice on whether to fire longer, hold longer or fire higher to fuse 3 layers rather than 2 - is there some sort of formula for depth of glass?
thanks, and sorry for the misinformation

[Zeldazog]

Just because there are more layers of glass, it doesn't mean that it needs any more heat or time to fully fuse - if it's the same formula glass, Bullseye for example, or whatever you're using, it will still process at the same temperature.

What you *do * have to do with thicker and also larger pieces of glass is extend the anneal soak time (that 483c) - because the larger/thicker pieces will take longer for the heat to become even throughout the piece.

That second program is way over doing it for something as small as an SC2 - you've got two anneal soak holds in there, I only hold my 30cm square pieces for 60 minutes, once.  You also only need one slow cool down between top and bottom of the annealing zone.

[flame n fuse]

3 layers will spread, unless you put dams round the glass

[Zeldazog]

3 layers will spread, unless you put dams round the glass

Good point, I missed that because I saw mention of tack fusing, where this wouldn't happen (with a tack fuse, you're only softening the glass enough to be 'sticky' not to make it fully molten)  

But it's good point and explains why you got a "blob" (depending on blob, your kiln could be over firing, too)

Glass likes to be 6mm thick, and when you full fuse, you are making your glass molten enough to be a liquid, about the consistency of honey perhaps, so if you have three layers of 3mm, it will simply try and spread out until it reaches that thickness and at 790c, that's near enough a full fuse.

[shafeenan]

Thank you SO much - such clear explanations.
Makes me feel a bit silly for not realising how/what happens. I've tried looking at the graphs that came with the kiln but being totally unmathematical they confused me further!
Now I finally understand what happens and - hopefully - where I am going wrong.
It will also save me hanging around for 13hour programmes!
I only did my first 'stand alone' firing on Jan 10th, so must learn to be patient with the learning process!
One day I will feel I can share a picture....I hope!