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The degradation and conservation of natural organic polymers from historic shipwrecks

Richards, Vicki Lewana (1996) The degradation and conservation of natural organic polymers from historic shipwrecks. Masters by Research thesis, Murdoch University.

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The aggressiveness of a shipwreck site towards submerged materials can be assessed by obtaining the physical, chemical and biological characteristics of that particular wreck site. To this end, environmental parameters and chemical characteristics of selected metal and organic artefacts were measured, in-situ, on a number of different shipwreck sites. Interpretation of these measurements allowed the predominant modes of degradation occurring on these marine archaeological sites to be determined. In addition, metal impregnated, waterlogged wood samples were analysed by spectroscopic techniques. The effects of the incorporated corrosion products on the extent of degradation of the waterlogged wood samples were assessed.

One of the major problems associated with the conservation of metal/organic composite materials is the detrimental effect of iron corrosion products on the post-treatment stability of organic materials. Therefore, a series of trials were carried out to determine the impact of different impregnants on the rate of iron removal from iron impregnated, waterlogged concretion, wood and rope. The rates of iron extraction were monitored and the effectiveness of treatments determined via physical, chemical and spectroscopic techniques. For concretion and wood, the optimal rate of iron removal was achieved by using aqueous solutions of 5% polyethylene glycol (PEG) 1500 and 20% PEG 800, respectively. The addition of citrate and dithionite to these solutions significantly increased the extraction rate of iron. For rope, a consolidation solution of 5% PEG 400, 2% glycerol and 1% ethulose combined with 2% citrate and 5% dithionite was found to give the best results.

A further series of experiments were conducted to determine the most appropriate consolidant for the conservation of friable, acid affected timbers from which the iron corrosion products had not been previously extracted. Interpretation of quantitative physical measurements allowed selection of the most effective consolidant system for the timbers. Of the consolidants tested, polyvinylpyrrolidone (10%) in n-butanol was found to be the most effective.

Degradation of aqueous PEG solutions was successfully monitored by measuring changes in solution pH and viscosity, Higher molecular weight PEG solutions of lower concentrations were more susceptible to oxidative degradation at ambient temperatures than more concentrated, lower molecular weight PEG solutions.

Item Type: Thesis (Masters by Research)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): MacLeod, I.D. and Ritchie, Ian
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