This section is from the book "Facts Worth Knowing", by Robert Kemp Philip. Also available from Amazon: Inquire Within for Anything You Want to Know.
A saturated solution of cyanuret of potassium, applied with a camel's-hair brush. After the marking ink disappears, the linen should be well washed in cold water.
Strong muriatic acid, or spirits of salts, applied with a piece of cloth; afterwards well washed with water.
Solution of muriate of tin, two drachms; water, four drachms. To be applied with a camel's-hair brush. After the writing has disappeared, the paper should be passed through water, and dried.
 
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