Methods & Aims in Archaeology

by W. M. Flinders Petrie

Pottery.

Pottery has not much to fear except salt, and that should be soaked out as from stone. Glazed pottery with salt in it is more difficult to clear, as it takes so long to get any change in and out of it. But a persistent soaking will clear it in the course of some weeks; and, if necessary, partly drying it in intervals, will bring the salt out of the cracks, whence it can be dusted off. The commonest failing of glazes is decomposition. The green turn brown, by the decomposition of the iron from green silicate to brown oxide; and this may take place from the porous interior without breaking the external face. The blue glazes go white; and this can be partly remedied by warming and soaking with paraffin wax, which fills the fine cracks and displays the remaining colour again. Sometimes the outer coat of clear glaze over faience inlay is decomposed, without spoiling the faience below. In this case it is like a picture of which the varnish is gone brown,—it only needs cleaning. The decomposed glaze can be scraped off, or rubbed with fine emery paper, until the faience is clean, and then a coat of paraffin wax clears the colour and preserves it from decomposition. When glazed ware, especially of the earliest times, is first found, it is very tender and soft. It then needs the most careful handling, and must not be brushed or cleaned until it is quite dry and hardened.

Textiles.

Textiles are also often saturated with salt, especially the Coptic garments which are in graves near the surface. They may be safely soaked to remove the salt and the organic matter, and then dried by pressing in a towel and laying between sheets of paper. The most tender examples might perhaps be best treated by placing with half a dozen sheets of blotting-paper over and under, and keeping wet below while evaporating on the top; this would carry the salt out to the top of the blotting paper. In any long soaking of organic stuffs a little carbolic acid is desirable, to prevent souring and putrefaction of the material. In every case the threads of textiles are liable to crumble, and any great amount of washing will tend to reduce a good deal to powder. Ironing is always desirable to consolidate the stuff.

Wood.

Wood does not suffer so much from salt as from rot and white ants. Any salt may be soaked out; or, if the wood is tender and will not bear that, a very stiff jelly should be made, so that it will just melt at boiling: the wood dropped in when the jelly liquefies, and left in the jelly cold for a week or two. Then the salt will dialyse out into the jelly, without any free water softening the wood. On remelting the jelly the wood can be removed, and the salt will be left in the jelly. The gelatine will strengthen and improve the wood. This process can be used excellently for ivories or bones, which would be ruined by soaking in water. Whole skeletons can be set in stiff size, and taken out weeks after, freed from salt, as was done to those from Medum, now in the College of Surgeons.

Rotted wood is very tender to handle; and from its continued contraction when exposed to the air it will fall to pieces. If nearly dry, but rotted, the best safeguard is to coat it with beeswax or paraffin wax; if it can be lifted threads can be slipped round it, and the whole dipped in hot wax until soaked. Or it may have a rapid coat of wax chilled upon it, which protects it and binds it together for travelling, and which can be soaked into it by piecemeal heating afterwards. If the wood will not bear lifting, it may be coated by dashing on superheated paraffin wax almost at boiling-point. This will soak deep into the wood like hot water, and consolidate it so that it can be moved quite safely. The same processes apply also to stuccoed wood, which needs such safeguards, as otherwise the stucco all falls off by the continued shrinkage of the wood. The great stuccoed sarcophagus at Hawara was preserved by heating the surface with a wire dish of charcoal burning about six inches above it, and flooding the surface with melted wax so soon as it was enough heated to absorb it. Perhaps superheated paraffin wax would have carried enough heat with it to soak in without the charcoal fire. For all heating of wax it is best to use a cast-iron saucepan, as soldered tins may give way before the wax boils. Another treatment, especially suited for large objects, is painting with several coats of wax dissolved in benzol.

Wood which is very wet is more difficult to manage. It may be kept for long under water, like the wood from the Glastonbury lake village. And it may be consolidated with silicate solution, as has been well done in examples from Silchester. Or it may be removed from water and laid in glycerine with the top exposed; thus the water will evaporate and diffuse, and glycerine take its place.

Ivory.

Ivory is mainly liable to flaking, especially if in wet soil. When any ivory is seen not in a firm condition, the earth should be carefully worked round so as to find the limits of the ivory, be it a single piece or a collection together. Then the mass should be under-cut down to a firm stratum, and lifted out in a whole block of earth. This should be left to dry slowly; and after a week or two the earth should be gently brushed away with a camel-hair brush, aided by picking with a stout pin. As each piece of ivory is seen it should be carefully followed, and if quite dry it may probably be removed entire. If still liable to flake, it can then be soaked in melted paraffin wax. If the ivory is too rotted to be detached from the earth, then the whole mass would have to be baked to rather over blood heat, and saturated with paraffin wax. After that it could be safely dissected by careful picking. In case of finding large groups of ivories in the ground, too extensive to take out in a block to dry, probably it would do to isolate them, then lay a few inches of sand on the top, and light a fire over them: after slow burning for a few days the ground would be baked dry below, and could be saturated with wax before lifting the mass.