Twice as dense??

[Flyingcheesetoastie]

Tried to answer Flame N fuses points last night but Iphone died, saving a novel of explanation!

Basically FnF is right, kinda, obviously if you are heating really slowly from room temp up to slump/fuse/whatever then the temperature of the outside of the kiln/ inside of kiln won't make a huge deal of difference.  For example, when I was at college we were taught to go up at like 75c/hour to 500c then either AFAP or slower to out top temp depeding on flow rate etc.  So basically that's 5 hours of gently heating the glass/kiln etc before you even get started.  I'm not saying this isn't best practice, but it's certainly not viable for me in my studio when I need to get kilns reloaded every day and as long as the annealing is sound then that's the main thing.

So when I fire my kiln, with say 3/4mm thick glass for a paint or slump firing (my bread and butter stuff) I want to go AFAP up to those temperatures because I know on the whole the glass isn't going to crack doing that and it's the cooling down where I want to be investing the time and electricity to get right.  BUT that breakage that occured recently happened in just such a firing wiithout any other factors apart from the kiln hadn't been fired for a few days and was very chilly at 8c.  So for me it was a reminder to go a little slower to allow the glass (insulator on the whole), the batts/props (insulators), kiln bricks (insulators) to heat up gradually too, because it was that sudden shock of heat hitting that glass when it was on a batt of 8c that probably cracked it.

Hope that helps to explain my vague reasoning behind programmes, chilly kilns & my perchant for kiln whispering!  I'm by no means an expert, but I'm well practised in what I do know!

[Zeldazog]

I think that's the main difference for us Rachel, I still fire quite conservatively (although not quite *that* conservatively) - because more than once a day isn't currently viable for me with various things - so a quicker firing time isn't a requirement - and I for one, do consider you an expert!

[Flyingcheesetoastie]

Oh I don't quite reload the SAME day, even that's a bit too kamikaze for me but most of my stuff is usually done in 18-24hours. Mind you when I worked at the stained glass studio, I've seen painted pieces go through 6 firings in a day with their gas kiln!

There are some things I don't have much experience of though like fusing multiple sheets etc. I would still need to look up firings and consult manufacturers handouts like the bullseye technotes.   But having a good knowledge of your kiln helps with everything.