casting-2

Casting glass 2

Casting glass 1

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This is my second attempt at casting a mirror blank, this time using a graplite mold that was sent to me by another atmer

The first pic shows the graphite mold filled with glass chunks, the glass was hand sorted to pick uniform
glass chunks about 1/2" in size. The kiln was turned up on high till the temp reached about 1450F, after
about an hour the temp was raised to 1650F but was still not melting evenly so I raised the temp again to
about 1780F. At 1780F the glass seemed to be melting ok but the bubbles on the surface of the glass
looked like mountains and would not "pop"so I raised the temp again to 1850F, at 1850F everything looked great until the temp rose to 1870F, at 1870F something went wrong with the thermometer and I had to finish the process, the second pic shows the mold being crash cooled to about 1100F to avoid crystal groth in the molten glass (devitrification)

This pic shows the glass blank while it was still in the mold, the glass had cracked
around the outside edge of the blank
probably because of uneven cooling but the glass had melted much better than the first attemp

With the help of some superglue, I glued
the blank together so I could get some pics of what the blank should look like

As you can see, the glass melted fairly uniform without many air bubbles

This last pic shows the blank between polarizing sheets, notice the 3 light spots
in the center rib?
This is stress in the blank caused by impropper cooling of the blank.
This is why annealing is so important.

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Casting glass 1

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