(2.) Wash the writing with a very weak solution of hydrochloric acid, then carefully apply infusion of galls.
(3.) For letters that have been in sea water, wash with warm water to remove the salt, then soak in weak solution of gallic acid, about 3 grains to the ounce. If this does not make the writing legible enough, wash thoroughly in clean water, and soak in a solution of protosulphate of iron, 10 grains to the ounce.
To restore writing effaced by chlorine.—(1.) Expose the writing to the vapour of sulphuret of ammonia, or dip it into a solution of the sulphuret.
|(2.)||Ferro-cyanide of potassium, 5 parts.
Water, 85 parts.
Dissolve and immerse the paper in the fluid, then slightly acidulate the solution with sulphuric acid.
Guitaud discovered that sulphuret of ammonia and prussiate of potash revives writing effaced by oxymuriatic acid.
To restore MSS. faded by time.—A moderately concentrated solution of tannin washed over the paper. The MS. to be carefully dried.
To preserve drawings or manuscripts.—Mix with every 100 parts of collodion 2 parts of sterine. Place the paper in question on a perfectly level and even surface, such as a marble table or large slab of glass. Give the paper a thin coat of this collodion, and in about twenty minutes it will be protected by a transparent, brilliant, and imperishable envelope.
To fix drawings or pencil marks.—Pass the paper through a bath of thin size, made either from gelatine or isinglass; or a bath of skim milk.
To render paper waterproof.—Take of borax 100 parts, water 2,250 parts; boil, and while stirring, gradually add powdered shellac 300 parts. When the whole is dissolved, strain through muslin. This will keep a long time and may be bottled.