Can I clean isinglass that is turning dark?
When you refer to turning dark, the first thing that comes to mind is brown spots or lines. If this is the case, then the clear plastic can't be restored at all. This is caused by either burning where the metal it hitting the plastic and getting hot enough to burn. Sometimes those brown spots will appear in other places, but the answer is the same, not it can't be fixed.
If you are seeing a diminished clarity, you could possibly reduce it to a certain extent using products such as Novus or Mequires clear plastic restoration products. That will be about as good as it gets. There comes a point in the life of plastic that it's finished and no amount of polishing can restore clarity. On the plus side, a creative fabricator might be able to replace the clear plastic.
Hope this helps.
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