Beautiful thick glass question
- August 13, 2014 at 8:33 pm #10182imakeglassParticipant
I’m fairly new to casting glass, but I wanted to try making a 1.5″ thick table-top, using 3 layered pieces of 0.5″ thick float glass. I understand I will need to dam it in (not sure how to do this though), but my main concern is how do I texture the bottom? Basically, I want to make what is shown below. Any help or comments are appreciated! Thanks in advance!November 13, 2014 at 5:48 pm #13403WildcatBethParticipant
I suspect you’d want to dam your piece using fiber strips and bullseye brick dams. You need to put the fiber paper between the glass and dams. While I’ve never worked with float glass and have not made any slabs similar to what you’re planning, I *think* you’d create the texture by fusing it on some fiber paper or fiber blanket that you’ve built designs and texture into. More than likely though, the texture was introduced using a sandblaster after the layers were fused together since its matte and so extremely textured. I’d experiment with the fiber paper thickness and designs with small pieces of float glass first to make sure it gives you the desired results. Finally, one other consideration since you’re making this as a table top, you’ll need to consider whether its tempered glass or not. Tabletops take a lot of stress and wear & tear…. Just some personal thoughts and considerations.November 16, 2014 at 9:18 am #13404Stephen RichardParticipant
For a project as thick as this there are firing considerations. You probably want a rate of advance no more than 50C/hr to 250C, 70C/hr to 540C, 100C/hr to 630C, 120C/hr to top temperature (possibly 740C) with a 10min soak. The annealing cool needs about 6 hours at ca. 540C, followed by 7C/hr for the first 55C and then 12C/hr to 110C below the annealing soak. Then a cool of 40/hr to room temperature. This is a two or three day firing.
Texture can be achieved with fibre paper scrunched up, or sand with aluminia hydrate powder on top of the sand to keep it from sticking to the glass. Tin side down will also help keep the sand from sticking. This is transparent not opaque, which a sandblaster would introduce.
Dams will be required, unless you are prepared to watch the firing. If you watch the firing, you will be able to stop the firing just as the top edge rounds and before it begins to flow. This will avoid the need for dams, and the subsequent cold working required. But note you will see the layers of glass on the edges. It will not appear to be a single slab.
This is something that you will need to experiment with for a while to get it right. It is very thick and heavy, so you may need help to place the glass in the kiln and to remove it when it is a single slab three times heavier than each piece you put into the kiln.
The thickness you are proposing will pass almost all existing strength and safety standards. Normally 19mm and thicker glass does not require toughening. The safety concerns are about it falling onto someone, rather than breaking.
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