Multiple slumpings in the same mould.

Sandera · February 22, 2013, 04:41:24 PM

In my eternal quest to keep costs down I am looking at slumping 2 items (each 6mm thick) of the same shape and size, one on top of the other, in the same mould, at the same time.

Has anyone attempted this and, if so, did you have to adjust the firing schedule and did the glass remain as 2 distinct pieces or did 2 become 1 (bah! Going to have that song in my head for the rest of the day now!).

I'm going to experiment anyway but any observations would be invaluable.

Zeldazog · February 22, 2013, 05:08:28 PM

I'd think that the underside of the top layer would afffect the top of the bottom layer, even if it didn't stick... and the two wouldn't come out the same shape (the inside of the bottom piece is smaller, all round, than the mould itself - and the shape would be slightly different too....

Can't say I've tried it and doubt I ever will.... I honestly don't think it's worth the risk of ruining two pieces of glass, (never mind potentially the mould if something went wrong) for the sake of a quid's worth of electricity - is your kiln particularly inefficient, or are your electricity costs that high?

Sandera · February 22, 2013, 05:19:48 PM

Quote from: Zeldazog on February 22, 2013, 05:08:28 PM
I'd think that the underside of the top layer would afffect the top of the bottom layer, even if it didn't stick... and the two wouldn't come out the same shape (the inside of the bottom piece is smaller, all round, than the mould itself - and the shape would be slightly different too....

Can't say I've tried it and doubt I ever will.... I honestly don't think it's worth the risk of ruining two pieces of glass, (never mind potentially the mould if something went wrong) for the sake of a quid's worth of electricity - is your kiln particularly inefficient, or are your electricity costs that high?

Thanks Zeldazog (or can I call you Zelda?!). No the kiln isn't too expensive to run but rather it's the time it takes to slump 1 piece as opposed to 2 pieces. I can only fit one, large, slumping mould in it and sometimes I have 3 or 4 pieces in a queue to go in which is a bit frustrating.

I wouldn't try it with coloured glass nor with my favourite mould. If it were to be successful then that might be pretty useful.

♥♥Tan♥♥ · February 22, 2013, 05:21:08 PM

Well Dawn has summed up all the important stuff and now I am just having a good old muse because I had never thought of this and its an interesting question..

Would you put a layer of thinfire between them to stop the pieces sticking together because if you did that would add onto the cost immediately.

I would GUESS that the bottom layer would be more of a defined shape with acuter angles than the upper piece but if you slump one on top of the other as Dawn has said you will lose the gloss on the top of the lower piece and end up with one muted piece and one glossy piece.

I'm really not sure about the stress on the mold, if it were stainless steel I would have a play but if it's ceramic I really wouldn't want to put it under all that stress just to see what happens, molds are blooming pricey.

Ermmm, would I adjust the firing schedule...........yes, I would probably reduce the ramp speed to about 100 to ensure a slow slump and even temp and have a longer hold time so the layers have time to think about what they are doing.

But if you have any problems with one like a bubble or a crack it is going to affect the other.

I wouldn't try this with a ceramic mold but I might with steel one, having said that I'm not sure I would want to slump two layers of 6mm each, it's interesting this, let us know how you get on, you're a pioneer my girl!

Pandanimal · February 22, 2013, 05:24:48 PM

Be very interested to see how you get on. I have never really done any fusing or slumping (the odd marble and bits of glass rod) and never used a mould. But you sound determined to give it a try so please do show us the result, success or failure!

Sandera · February 22, 2013, 05:26:54 PM

Thanks Tan. I think your concerns re using a ceramic mould are likely to be well-founded so I will try it out on a steel one and let you all know how I got on. Thanks for the tip re the firing schedule as well.

I'm really glad I posed the question as it's giving me food for thought!

Zeldazog · February 22, 2013, 05:42:57 PM

Quote from: Sandera on February 22, 2013, 05:19:48 PM

Thanks Zeldazog (or can I call you Zelda?!). No the kiln isn't too expensive to run but rather it's the time it takes to slump 1 piece as opposed to 2 pieces. I can only fit one, large, slumping mould in it and sometimes I have 3 or 4 pieces in a queue to go in which is a bit frustrating.

You can call me Zelda (it originates from Terrahawks not the Nintendo game); or Dawn

I get what you mean about the frustration of only fitting in one mould at a time and the wait, but at least you can set it and walk away and do something else. The trouble would come if you start getting more orders per week than you can physically fuse and slump in a week.

Sandera · February 22, 2013, 06:22:21 PM

Quote from: Zeldazog on February 22, 2013, 05:42:57 PM
Quote from: Sandera on February 22, 2013, 05:19:48 PM

Thanks Zeldazog (or can I call you Zelda?!). No the kiln isn't too expensive to run but rather it's the time it takes to slump 1 piece as opposed to 2 pieces. I can only fit one, large, slumping mould in it and sometimes I have 3 or 4 pieces in a queue to go in which is a bit frustrating.

You can call me Zelda (it originates from Terrahawks not the Nintendo game); or Dawn

I get what you mean about the frustration of only fitting in one mould at a time and the wait, but at least you can set it and walk away and do something else. The trouble would come if you start getting more orders per week than you can physically fuse and slump in a week.

That's the problem Dawn! I'm trying to balance the viability of the business whilst growing it at a sustainable rate. I'm finding it quite difficult to keep up with things at the moment whilst also giving myself time for development and experimentation. And the profit margins are very tight. Maybe I just need to acknowledge that I'll be lucky to break even

Anyway this idea is a bit of a shot in the dark but I'll happily share the results.

♥♥Tan♥♥ · February 22, 2013, 06:27:48 PM

Playing and experimenting is learning

Sandera · February 22, 2013, 06:31:46 PM

So much to learn, so little time

Glyn Burton · February 22, 2013, 08:11:37 PM

Molds normally have a small breather hole which allows the air to escape as the glass slumps in. I would have thought that there would be a strong possibility of air being trapped between the two sheets of glass and blowing bubbles.

firedinglass · February 23, 2013, 08:35:02 AM

iI just don't think this will work. The shape will not be true on either, the polish will be non existent on the top side of the under dish and the top dish will not have a flat base. ...

MeadMoon · February 23, 2013, 11:30:37 AM

I also have doubts about it working for two separate pieces, but it could produce something quite original - although not what was intended. I'll be very interested to see what happens if you do decide to try it.

Sandera · February 23, 2013, 08:48:51 PM

Quote from: Glyn Burton on February 22, 2013, 08:11:37 PM
Molds normally have a small breather hole which allows the air to escape as the glass slumps in. I would have thought that there would be a strong possibility of air being trapped between the two sheets of glass and blowing bubbles.

That's true Glyn. Mmm....this is looking distinctly less feasible. But ....I'm going to try it anyway just so we know!

Sandera · February 23, 2013, 08:55:04 PM

On another note re slumping: I'm doing a short mould making course and the tutor is eager to personalise the session to include mould making for glass. I think the others on the course are ceramicists. I suggested that it would be useful if I could make a couple of slumping moulds. Does anyone know what material commercial slumping moulds are made of? Is it clay?