Mica is a pure mineral and it won't deteriorate or discolour unless some contaminant has seeped in between the layers. You see sheet mica in old toasters and heaters that has remained clear or perhaps gone a little dull on the surface after 50 years or more but not the opaque tan you may see after heatsink duty, so perhaps its oxidised or otherwise contaminated silicone oil you're looking at in there.
No doubt someone has some better evidence or is more certain of what really goes on but unless there is some pressing need to save the old washers or they are only in light duty use, why not fit new and rest easy?
No doubt someone has some better evidence or is more certain of what really goes on but unless there is some pressing need to save the old washers or they are only in light duty use, why not fit new and rest easy?
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