# How the heck do you figure the amount of glass needed for a large square drop so that you end up with a 6mm thicknes?

Home Forums Glass Fusing General Fusing Discussion How the heck do you figure the amount of glass needed for a large square drop so that you end up with a 6mm thicknes?

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• #10301
kingofkings
Participant

We have the wonderful pot calculator, now I can’t seem to wrap my head around what amount of glass, how large my blank needs to be to end up with a deep square.  And if I should use a drop ring with SS sides to help the drop or make a mold from a wet fiber blanket. Futhermore, if I use the wet fiber blanket do I drop into it cause draping would cause wrinkles? My boss gave me a cracked 11 3/4″ square glass container that she’d like to be between 3″ and 8″ deep and possibly have a small lip on it. I need engineering.

Sheila

#13567
Stephen Richard
Participant

Are you trying to do a pot melt into a shaped mould?  If so you will have a shaped bottom and a flat top with no depression.  If you mean to melt to a square and then slump it, that is a different proposition.

But answer the question put in the first sentence. Measure in centimetres – the calculatons are much easier.  the thickness is 0.6cm, if you want a square 30cm square you multiply length time width times thickness.  30 x 30 x 0.6  = 540cc.  Multiply this by the specific gravity of glass (2.5) = 1,350 grams of glass = 1.35 kg = almost 3 lbs.

If on the other hand you mean to have 6mm thick walls on the drop, you are asking a completely different question.  A 75mm drop will require less glass than a 200mm drop.  I would guess – and it is complketely guess work – you would need 12-15mm slab to start with.  For 200mm, maybe 25 -30mm slab would do it.  The problem is the sides.  They thin dramatically as the glass heats up.  So the thicker the glass bottom the faster the glass will fall and stretch thinner.

Seems to me to be better, if you really want to do this, to emulate the Norman slab process.  In this the bubble is started and then blown into a tall square steel mould.

Stephen Richard

#13568
kingofkings
Participant

Thanks Stephen.  I’m not trying to do a pot melt. Just seeing if it is at all feasible to take a thick blank and make a square boxed bowl. Whether (1) drape it over a hardened fiber blanket or (2) slump by use of a drop ring aparatus with SS sides to help make the square, square once it’s dropped.

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