Many curators dry carefully and impregnate them with a gum-dammar solution or shellac; isinglass or glue are however preferable, for these aqueous solutions may be used for the treatment of damp objects, which could scarcely be dried without cracking. In order to permeate the object these solutions must be very dilute, and are most advantageously applied at a temperature of about 120°F. [50°C.]. The impregnation may also be effected in rarefied air under a bell glass (p. [68]). Friable bones and similar objects which might fall to pieces in the solution during impregnation should be bound with strips of gauze or with string before immersion; they are easily removed when cold. To prevent the formation of mould a small quantity of dissolved corrosive sublimate[163] is added to the glue, or when dry after impregnation the objects may be covered with a solution of shellac or resin. Impregnation is of very general application, and is frequently used for the preservation of fossil and pleistocene bones.
(o) Leather.
At Copenhagen the method used to render leather soft and pliable is to place it in train oil for an hour and then dry it with filter-paper. Lanoline may also be used with success[ [164]. Poppy-seed oil in benzine (p. [86]) is said to produce good results, but the “Merkbuch” recommends the preservation of leather in this condition in alcohol[165].
(p) Textile Fabrics, Hair.
Earth and soil may be removed by mechanical means, and, occasionally, careful washing may be possible. The objects should be dried and impregnated with a gum-dammar solution (p. [70]), poppy-seed oil (p. [86]), or a solution of india-rubber (p. [90]), or they may be preserved in alcohol (p. [159]). Some textile fabrics in the Copenhagen Museum owe their excellent state of preservation to Steffensen’s treatment, i.e. impregnation with a solution of india-rubber in turpentine with the addition of bees’-wax.
The following account of the treatment of textile fabrics from the Lake-Dwellings is due to Herr Heierli, of Zürich:
“The pieces as they were taken up were laid on the ground and thus slowly allowed to dry in the air. They were then placed between glass plates, the edges of which were pasted over with paper. Old pieces which had been dry for a long time, and which had become tender and friable, were laid on the ground and watered from time to time until they were soaked through; they were then treated in the manner already described.”
Egyptian textile fabrics preserved between glass plates often deposit a thin layer of salt on the glass, but this is easily wiped off (see p. [155]). It must first be ascertained by a previous trial in each case whether the salt can be removed by steeping in water or in alcohol and water.
Hair found in peat has always a dark-brown colour from impregnation with peaty matter. The method proposed by Bille Gram[ [166] for restoring the natural colour consists of repeated and alternate treatment with very dilute alkali solution and acid at about 120°F. [50°C.]. When the liquid ceases to show coloration the natural colour of the hair is restored.