Preventive Conservation

Wet organic objects are often incomplete and are generally more degraded than their dry historic counterparts. Extra care is needed when handling, storing and displaying these objects.

Environment

Store and display treated wet organic artefacts under the conditions recommended for the material type in question. These may be obtained by referring to the relevant chapters of this book.

As for all materials, the key to improving the stability of wet organic objects is to maintain appropriate conditions that are as steady as possible. This is particularly important for wet organic materials, as in many cases the proteinaceous or cellulosic components of these materials will be substantially degraded.

Extra consideration and care should be taken with:

• cellulosic-containing objects that still contain iron corrosion products and reduced sulphur compounds; and
• objects for which incorporation of consolidating chemicals was necessary.

In both of these cases special attention may have to be paid to the environmental conditions to prevent continued deterioration of the treated artefact. For instance, under conditions of high relative humidity, oxidation and hydrolysis of incorporated iron corrosion products and sulphur compounds can lead to increased acidity and subsequent damage to dried, formerly waterlogged wooden objects. Maintain relative humidity levels of less than 55 % in order to prevent this type of deterioration.

The incorporation of polyethylene glycol (PEG) into an artefact will affect its response to its environment as low molecular weight PEGs are hygroscopic. Under high relative humidity conditions, PEG-treated artefacts may take on a sticky, greasy appearance. Mould formation and bacterial attack also are enhanced by the presence of a food source such as PEG and by high relative humidity conditions.

Handling

Many formerly wet organic archaeological objects are more degraded than their historic counterparts and consequently require more careful handling. For fragile objects, the construction of supports that allow them to be handled without actually touching the objects themselves is recommended.

Whatever the final choice for a support it should allow the object to be manipulated with minimal risk of damage. A support that is suitable for both storage and display is probably the ideal. Choose the support on the basis of the fragility of the artefact and its future use, be it storage, display or research (see the chapter Handling, Packing and Storage).

In all cases the media used to construct supports must be of archival quality and compatible with the artefact. Acid-free materials in contact with proteinaceous artefacts such as leather and silk, for example, should not contain alkaline buffering agents as these substances increase protein hydrolysis (see the chapter Preventive Conservation: Agents of Decay).