Friday, April 2, 2010

Casting - How do I Account for These Results?

The first results are in.  The first casting/fusing of the nice, cheap Guardian float glass is complete and I'm at a loss to explain what happened.  The first part of the story is here.  This first picture is a bucket of cullet.  It was approximately $4 for 40-50 pounds.  Great price.

Even in the bucket, this stuff looks great.  Even though it is a "float" glass, the type of glass used in windows, it doesn't show the usual greenish tint.  The picture below shows some pieces laid out on a paper towel, to give you an idea of how crystal clear it is.

So I piled up a bunch of this stuff in a 9" casting ring in the kiln.  It probably was a little over two inches high in most spots.  I knew it would melt down and I was going for about an inch and a half in thickness.  I understood that there would be lines and ghostly images where the various chunks where, but overall I thought I'd get a fairly transparent disc of glass.  Instead this is what I got.

This was melted at 1500 degrees (F) for 120 minutes.  The surface is quite bumpy still, and you can clearly see the outlines of every chunk of glass.  The texture is fairly smooth, and doesn't feel like devitrification, which in my experience is quite rough and "crackly".  The bottom is fairly smooth as shown below.

The bottom is a little closer to what I expected, but still it is very cloudy - not clear at all.  Anybody have any thoughts?  I haven't worked with float glass and am a little puzzled.


  1. Hi Jeff - I come here every so often, but I've never commented. Don't know where in the 1,000 viewers I stand!

    I think that's devit even though it doesn't seem like the "usual" kind. I know what you mean about really rough devitrification. I've had some on opaque glasses - especially white - that seems to have grown like a fungus and is really raised.

    I recently dug out some smoke-colored float. It was a window in a business where I used to work that had shattered (it was tempered.) I put it on the kiln shelf roughly in the shape of a platter mold I have and fired the bejeebers out of it. It still has the texture of all the little pieces and it devitrified. The devit is foggy, but smooth, like it was sandblasted in spots. Could that be what your float did?

  2. Hi Bev, thanks for looking. I'm way behind in posting as I always get busy. I think the "sandblasted" look is a good description. It grinds off and gives a nice ethereal look.