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I intended to make a bowl of a 30 cm circle of 10 mm glass, sandblasted and coloured, then slumped into a ss mould, diameter 30 cm, depth 15cm. However, I've been told that this mould will be too deep for the glass and that I'll get roll over of the top edge, which obviously will spoil the end result. What would be the deepest mould I could use to prevent roll over? If it's fairly shallow, I'll change the design as the one I had in mind wouldn't look right on a shallow bowl.
many thanks
Cheryl

It's not the depth of the mold, it's the shape. What you propose can be done in lots of molds, perhaps not in some others. If I calculated correctly, you want to slump a 5/8"(?) thick, 12" bowl into a 12" mold that is 6" deep. The glass is gonna move and as I said above . . . . Brock

Brock wrote:It's not the depth of the mold, it's the shape. What you propose can be done in lots of molds, perhaps not in some others. If I calculated correctly, you want to slump a 5/8"(?) thick, 12" bowl into a 12" mold that is 6" deep. The glass is gonna move and as I said above . . . . Brock

10mm is 3/8".

Cheryl. The steeper the shape, the trickier it is to get a clean slump. The glass will tend to wrinkle and fall asymmetrically in to the mold. This might be very interesting. If not you might try 2 slumps. One in to a less steeply shaped mold and then the final slump. Lower temps and longer soaks might help.

There is the Brock shuffle where you reach in with kevlar gloves and adjust how the glass sits in the mold. This could be quite difficult in a steep sided mold. Watch out for singed hair and don't wear polyester clothes.

It's the Craig shuffle. Brock

Cheryl Wade wrote:I intended to make a bowl of a 30 cm circle of 10 mm glass, sandblasted and coloured, then slumped into a ss mould, diameter 30 cm, depth 15cm. However, I've been told that this mould will be too deep for the glass and that I'll get roll over of the top edge, which obviously will spoil the end result. What would be the deepest mould I could use to prevent roll over? If it's fairly shallow, I'll change the design as the one I had in mind wouldn't look right on a shallow bowl.
many thanks
Cheryl

Do you mean roll over outside of the top edge, Cheryl?

I've had a 380mmDia disk 12mm bigger than the (ceramic) mold, it slumped into the mold no problem. Seems the weight of the glass 'hanging' in the middle pulls the glass into the mold.

In doing so, it also pulls in the excess material overhanging the mold on the outside of the rim. So in a wird, I found that it shrinks in diameter, to allow for the material dropping into the mold.

Or do you mean that you forsee happening a crinkle/ripple in the edge?

Brock wrote:It's the Craig shuffle. Brock

Oh... I got confused. Is that dislescic?

Bert Weiss wrote:

Brock wrote:It's the Craig shuffle. Brock

Oh... I got confused. Is that dislescic?

No. Dyslexic. Brock

Hello everyone

Sorry for taking so long to reply, I must have inadvertently unticked the "notify me of reply" box when I posted. I thought it was a bit odd that no one had replied so checked today.

Brock - the shape of the mold is a hemisphere with a small flat bottom (or is that me I'm describing?)

Paul - I did mean wrinkling and folding inwards of the top edge rather than rollover on the outside of the mold, I thought that the thickness of the glass would encourage it all to slump inside especially as the mold I had in mind has a slightly inward sloping rim.

Bert - I like the idea of slumping in two stages; I'll try that and with lower temps and longer soaks.

I have found another ss mold now that I'll use, still 30cm diameter but only 8.5 cm deep - what's half a hemisphere called? - so a shallower drop which should help keep the integrity of the glass, I hope. It should be interesting anyway.

Happy New Year to everyone

Cheryl

Might not be practical for glass that thick, but one way to drop into deep molds in one step and have it nice and even is to put a rim on it, then cut the rim off. Like a drop out into a form.

Hi Cheryl,

As Bert mentioned, the disc might tend to move as it gets hot and shift itself to where it wants to be.

I found that whilst using this mould;

HF 052 Round Bowl
ø 40 cm, Depth 8 cm

(For illustration purposes, courtesy of the Bohle website.)

if I use thin glass, it seems to slump evenly, the edges stay in place on the mould as the centre drops into it.

Then if the glass is 10mm float, I find the sheer weight of the glass will cause it to relocate itself, kind of like a fried egg sticking on one edge in the pan and the rest of it moves, you know what I mean? So the result is a lop-sided affair and my good lady says it has character but she might have a biased opinion...!

I think what I'll do is try it with an unworked piece of float - why waste the sandblasting etc? - and see what happens. Maybe my husband will be as courteous as your lady Paul. If it's not too horrible I'll let you know what happened, if I can work out how to post a picture.

"When you know, you can never go back." Sort of like Father Christmas - that's sad.

Cheers
Cheryl