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Old 04-14-2019, 03:52 PM
Shawn Everette Shawn Everette is offline
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There is no getting around mass, but venting should help. You need to be somewhat careful about to to prevent thermal shock. Pete is right about venting to 1100, but let it bounce up and vent again, rinse, repeat. If you're using bullseye you may need to hold at 1200 to prevent "suckers", weird areas where the glass pulls away from the mold. They don't have a great explanation on why it occurs, but I have seen it.

The billets and plate should be relatively the same glass. They're both compatible, flow the same, and nothing in your cycle changes. The biggest difference is the color saturation. Transparent fusing glass is designed to be less dense than a blowing color because it isn't going to be stretch much and is usually used in a 3-6mm application. Casting glass is even less dense because most castings are going to be much thicker than that. Casting glass can have lower viscosity, but bullseye's nor specturm differentiates cycles between billet/rock or frit/plate. Both need to be fires 1500+ to get any kind of flow. There is even some gibberish I just read that was saying that bullseye's surface tension increased past 1550.

If you decide to stick with the flower pot method I highly suggest kilns that are top fired, and using the widest possible vessel you can find. You will get significantly faster melts.

If you are not using billets then you are always going to have some form of veiling. The plate and frit that you load into a kiln is going to have a much greater surface area than a billet, and more surface = more imperfections. It is inevitable that the broken glass remelting is going to trap those imperfections, and you are not going to get to a high enough temperature in a casting to have those fine out. Glass doesn't readily go back into solution unless you are at temps well above a casting.

Quality casting glass is always going to be more expensive. Purity has to be extremely high, shipping is pricey, and the demand is lower. I wouldn't hold out on Oceanside producing rocks anytime soon, and the verdict is still out on QC. Gaffer is going to give you a lower temp glass with a wide pallet. It's great that you want to make your own to be economical, but you're really searching for a different base formula than blowing or fusing.

The orb we made was solid glass. I suggest finding some football players and teaching them how to turn pipe.
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