With careful handling, my kaleidoscopes should last a lifetime. The oil from skin will eventually break down the lacquer that preserves the finish. There is brass polish made for surfaces that have been lacquered available at hardware stores.
To clean a kaleidoscope, lightly spray some furniture polish on a cloth and wipe the barrel and the brass fittings.
To clean the glass, spray some window cleaner on a paper towel and gently wipe the objective and eyepiece until they are clear.
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