New materials used for the consolidation of archaeological wood – past attempts, present struggles, and future requirements

Journal of Cultural Heritage ( ISSN 1296-2074) Vol. 13, hefte 3, 2012, ss. 183-190.

Mikkel Christensen, Hartmut Kutzke og Finn Knut Hansen

Given the perilous state of the Oseberg find from Norway, the Museum of Cultural History and the Department
of Chemistry both at the University of Oslo, are looking into new methods for treating archaeological
wood. While numerous polymers have been previously tested, most do not stabilise the wood sufficiently,
penetrate far enough, or remain stable without producing toxic fumes. A few of the more common examples
are: Alum salt, KAl(SO4)2·12H2O, which was used for treatment earlier but does not penetrate well
and leaves the wood very acidic. Poly(oxy ethylene) (POE or Polyethylene glycol [PEG]) is widely used
as a consolidant today but this material degrades over time and thus cannot support the finds for a very
long time. Melamine-formaldehyde (Kauramin) has also been used and while it is fairly stable, it may
also fill the wood and turn it into a ‘block’ of plastic. Since new consolidants would be advantageous, it is
discussed what the requirements of such consolidants are and how material sciences may help procure
them. It is proposed that an important requirement for a future stabilising agent is to leave an airy structure
in order to allow retreatment in the future. This might be accomplished by foaming a polymer, or
by combining nanoparticles with a polymer ‘spider web’ network to keep them in place. Such particles
may help stabilise pH inside the wood by neutralising any acid generated inside treated artefacts. Special
attention is given to the field of biomimetics–the discipline of constructing materials inspired by existing
natural designs. It may be possible to construct a frame using bio-inspired materials (possibly an ‘artificial
lignin’ mixed with other compounds optimise strength and flexibility) or through biomineralisation (an
inorganic ‘skeleton’). Tests on biomimetic cellulose and chitosan have begun and the initial evaluation of
these materials is given. Chitosan is made from modified chitin (primarily from shrimp and crabs) and
may be dissolved in acidic solutions. Crystalline cellulose is interesting in conservation as the individual
particles are resistant to acid and not as hygroscopic as the amorphous part of cellulose. The materials
and the procedures used in testing are described. It is shown that crystalline cellulose particles usually
flocculate when used to treat archaeological wood but that they may be treated with surfactants in order
to improve penetration of archaeological finds.

Publisert 12. nov. 2012 12:16