This section is from the book "Cassell's Cyclopaedia Of Mechanics", by Paul N. Hasluck. Also available from Amazon: Cassell's Cyclopaedia Of Mechanics.
Gold braid only slightly discoloured may be cleaned by beating it with a soft brush dipped in fine whiting, calcined magnesia, or fuller's-earth. If badly spotted and blotched, the stains may be removed by carefully brushing with a brush dipped in a warm solution of potassium cyanide - 1 dr. to 1/2 pt. of water - then in clean warm water. If the braid is of poor quality, all attempts at cleaning will only make its appearance worse.
 
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