Home Made Billets

You can make your own billets from small pot melts.  But why should anyone go to the effort? Some reasons are:

• ·        You can make your own colour. 
• ·        You can use your cullet/scrap (avoiding buying or making frit).
• ·        You don’t have to buy and break billet to size 
• ·        You can reduce the clouding caused by many microscopic bubbles surrounding the frit pieces. 
• ·        You can make a size to fit your casting mould. 
• ·        Potentially, you will reduce needling.

 Now you are convinced of the advantages, you want to know how.

Preparation

• ·        Select the glass. Avoid iridised glass and any ground edges – they will cause haze in the final casting. Wash all the glass. Place the glass in a small flowerpot.
• ·        Weigh out the amount of glass cullet needed for the mould and add about 50gms to account for the glass that will stick to the pot.  Calculating the required weight is relatively simple and this post gives the information.

Dams

• ·        Arrange dams in such a way that the resulting billet will fit into the mould without overhang.  It might be quite a tall billet. In which case cast it horizontal with the height as the length of the billet.
• ·        Line the dams with Thinfire/Papyros at least. One mm fibre paper would be better. 
• ·        The dams can be on a kiln washed shelf or on fibre paper. The bottom of the glass will be fine either way.
• ·        Place the pot above the dams.  The higher, the fewer bubbles in the billet.  And any left in the billet will be reduced by flow in the casting firing.
• ·        Multiple billets can be made of different colours, sizes, etc., at the same time.

Firing

• ·        Fire to around 900ºC/1650ºF and soak for hours.  Observation will show when the pot is empty.  Clue: There will be no string of glass from the bottom of the pot.
• ·        Anneal as for the smallest dimension.  If you are doing multiple sizes, the dimension must be taken from the biggest piece.
• ·        When cool, remove and clean the separator off the pieces thoroughly.  A 15 minute soak in a 5% citric acid solution will speed the process.

Casting

• ·        Place billet in casting mould. The first ramp rate needs to be for the smallest dimension of the billet.  This may be a slower rate than when using frit for casting.
• ·        Do a long bubble squeeze in the 650ºC to 670ºC range – up to two hours, but a minimum of one.
• ·        Fire to your normal top temperature and time.
• ·        Anneal for the largest piece.

 

More information here