Slumping Glass
Slumping Glass - why make moulds?
- If you want to texture or shape glass with a unique pattern before leading it into a panel
- If you want to create a stained glass panel with a particular motif or contour
- If you want to make multiple pieces with the same textural design
What are moulds made of?
There are a huge variety of commercial moulds that you can buy for
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slumping glass. These range from small ashtrays to huge bowls. There are also moulds to slump glass into, over and even through. You could also use metal bowls or found objects as a mould. There are two important thing to remember:
- the material must be able to withstand temperatures of up to 800C in the kiln.
- that you use a separator (bat wash or powder) to prevent the glass from sticking to the mould
Types of mould
1Plaster-based moulds
2 Clay moulds
3 Fibre paper moulds
Which type of mould should I choose?
This depends on what result you want to achieve. Each method has positives and negatives:
Plaster-based moulds
Good for detailed textures and difficult shapes. Allows flexibility. Only lasts for 1-3 firings. The messiest, most time-consuming technique, but the one that allows the greatest freedom. Requires a week to dry out, depending on size.
Clay moulds
More durable than the plaster moulds, so good for any projects that requires multiples. Good for detailed designs. Easily formed. Needs to be bisque fired first. You have to work in negative, so not for the spatially challenged!
Fibre paper moulds
Good for larger, flatter pieces of glass. Good for simpler, less detailed and bolder work. By far the quickest method. Limited design opportunities.
General tips
a) Try not to make a mould that has very steep sides and is too deep.
b) Drill small holes to prevent air trapping and causing bubbles.
c) Make sure the mould is level before firing.
d) If possible, the moulds should be uniform in thickness.
e) Make sure there are no undercuts.
f) A level surface with a 2-3cm lip is necessary for any projects that need leading.
g) Objects coming in contact with mould mix need to be covered with a separator – eg petroleum jelly – to help their removal once the mix has set.
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