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Durability Many of the batches we have analyzed have shown scant attention to durability, while others seem somewhat over the top. Alumina is the most effective cheap agent to make a glass more durable, but too much leads to a glass that is more difficult to melt. At melting temperatures, 2% Al2O3 can push up the melting temperature for the same viscosity by as much as 35oC (nearly 100oF). Gaffer batch contains a much smaller amount of alumina, but supplements it with zinc oxide, which is as effective as alumina in resistance to water, steam and acids, but lowers viscosity/temperatures at the same time. Testing by Integrix3 shows its durability to water and acids, lies comfortably within industry guidelines for container glasses.
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