Help needed please

[Glassy Lou]

I'm currently using this mould http://tempsfordstainedglass.co.uk/acatalog/info%5f1KSM7001%2ehtml that I bought last week (first time if using) and it's cracked while heating up and the glass has leaked onto the kiln shelf.

I'm not sure what to do. Should I let it carry on or stop the kiln? (It had got up to about 700 degrees c)

Cheers for any help

[Jane C ♫]

Either way, your mould is stuffed and you'll need a new kiln shelf.

I'd turn it off. Or forward the programme on to its annealing cycle and then let it cool.

Means the glass won't run over the rest of your kiln / the elements.

Take pictures. Contact Tempsford with details of the firing cycle you used, and the pics of what happened. They may be able to replace your mould free of charge, and possibly the shelf if you ask nicely ....

[Jane C ♫]

PS I had a big mould from Warm Glass crack on its first firing - I sent them pics of what happened, and the firing cycle I was using. They checked with their tech guys and then sent me a new mould. Thankfully mine was just a slump firing so the glass didn't escape!

You may be able to chip the glass off the shelf later, or use the other side of it, depending on how much has escaped.

[Glassy Lou]

Thank you Jane. I did turn it off in the end. I figured it was screwed so didn't want it going any hotter.
I'll take some pics when it's cooled down.
I'm gutted though 

[Flyingcheesetoastie]

Do you pre-fire your ceramic slumping molds?

[Jane C ♫]

Aww Lou! Not surprised - you poor thing.

Flyingcheesetoastie has a good point - did you let the kilnwash / spray dry for long enough before firing? If your mould is a bit damp that can crack it as the water expands.

I normally chuck mine in the /normal/ oven for a bit to make sure they're really dry, if I've got any doubt at all, or go on a reeeeeally slow ramp.

[Glassy Lou]

I kilnwashed it about three days ago so it was well and truly dry
It looks as though it was my own silly fault. I'd programmed the kiln to ramp up way too fast. Something like 400°c per hour - think I've read the °f instruction instead of °c

The good news is that I managed to chip the melted bit of glass off the kiln shelf without causing any damage to it so I don't think I'll need a new one. The mould on the other hand is well and truly jiggered so it's off in the bin!

It's typical tho - yesterday I managed a successful first attempt at a plate slump so I was really happy. Might have been the best thing - bring me back down to earth with a bump so I don't get too carried away hehe

Thanks guys x

[Jane C ♫]

Oh whoops! But really glad you worked out what happened and managed to save your kiln shelf.

[Flyingcheesetoastie]

Most ceramic molds I've bought have come with a pre-firing programme to completely dry them out and expel any water/chemically bonded water within the ceramic too.

I'll have a look for one at the studio and post it as I've used it on molds from 15cm square to 60cms diameter.