Ghost lines

[Lauri Levanto]

I have used reject "pilt" glass fron a local glass factory.
It is broken pieces of clear glass vases, about 1 cm thick.

When I fill a flat open face relief mold with a layer of
this frit, the fired piece has thin opal lines thru as if there
were spider webb in the glass.

When casting in a deeper mold, the glass stays clear with
some bubbles in. Flower pot casting gives areaaly
clear piece.

I guess the ghost lines are micro bubbles that get trapped
between the shards. How to avoid them. As I understand it,
the more the glass is moving during the melt, the less
ghost lines there will be. In a flat relief mold the glass flows
only a little.

Is there a way to avoid ghost lines in a shallow cast?
-lauri

[Carol Craiglow]

Have you tried taking the shallow casts up to a higher temp (1700F or so) to get the bubbles to rise to the surface? I guess if you're doing that, using the flower pot method would work just as well. Anyway, that's about the only thing I can think of.

Good luck and let us know if you find a solution!

[Kevin Midgley]

To get clear glass, it needs to be a pot melt or equivalent system. What would the factory where you are getting your glass suggest to use as a flux? Do they have any suggestions? My suggestion would be to learn to like the lines! Kevin in Tofino

[Tim Lewis]

It could also help to wash the glass. Some of the fine ground glass from the shop floor or in shipping will stick to the glass and leave "halos" in your pieces. To make the halos show up more sandblast the pieces first.

[Lauri Levanto]

Thanks to everyone.
I'll wash the glass more carefully, melt the flat pieces
to a higher temp and load the relief molds unevenly, so that
the glass moves more while melting.
I'll experiment with flux, too.