[morzh]

Well, I cleaned all my capacitors either with dish soap and hot water, soaking it first and then using liong soft brush (although as the experience showed me, brush was not necessary - running water took care of everything after soaking), or, in case of old big ones, like from Philco 20, dishwasher cycle with cascade took care of it also well. It will not be sparking after that but a little dulling does not affect performance.

Dry thoroughly after that which is simply done by blowing the excess water with compressed canned air, and then leaving on a paper towel overnight at regular room temperature. In my recent posting about Stromberg-Carlson you can see the cap after that cleaning, and the blades came out very nice. The rods were darker but this is patina which could not be simply washed off and I am unwilling to subject a tuning cap, it being a rather delicare creature, to a harsh mechanical treatment.

In any case, even if you decided that you do not want any sparkle there, simply blowing the dust out with compressed air (not too strong, could bend the blades otherwise) will render it fully operational.