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LightningInAJar
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I could swear I saw this topic in the forum in the past but haven't found it today. I was curious how polarization test cards are made to prove that a pair of glasses are polarized. Special ink or paint? What is that type of substance called or commonly used for? I'd love to use it for art. Does it require special paper medium? Anyone ever make printer ink cartridges with an ink invisible only without polarized glasses?