4 CONCLUSIONS

The biodegradation incurred by the historic undyed sample was due to two types of cellulolytic micro-organisms in the deep-ocean environment in which the sample was submerged. One type was rod-shaped and attacked the cotton fibers layer by layer, creating an exposed fiber interior with characteristic grooves of about the same dimension as the rod-shaped micro-organisms. The other type was oval-shaped and penetrated the fiber wall, creating holes of about the same dimension as the organism. The presence of two types of microbial damage, as well as of iron sulfide deposits, reflected a combination of both anaerobic and aerobic conditions. The sequence in which these processes occurred remains to be determined.

The historic dyed sample fiber was less degraded than the undyed sample fiber, even though the two were from the same item of clothing and had experienced the same long-term storage environment. The growth of these cellulolytic micro-organisms was inhibited in the dyed cotton by the presence of a tin mordant that acted as a biocide.

Upon treatment with 18% NaOH, localized fragmentation was observed on the fibers removed in the historic undyed sample, a consequence of the localized microbial degradation. The higher degree of swelling of the historic undyed specimens demonstrated overall damage of the primary wall incurred by the undyed fiber specimens in comparison with the dyed specimens. Fibrillation was observed in both the dyed and undyed samples that were treated with a mixture of sodium hydroxide and carbon disulfide, as opposed to the balloons observed in the new samples indicating that both historic materials experienced some damage to the primary wall. One unique feature more frequently observed in the historic undyed samples was horizontal surface fragmentation or splitting. As conservators work with marine textiles, they must be aware that the environmental conditions and the types of degradation are different from terrestrial materials, and these differences may influence treatment decisions.