JAIC , Volume 39, Number 1, Article 7 (pp. to )
JAIC online
Journal of the American Institute for Conservation
JAIC , Volume 39, Number 1, Article 7 (pp. to )




Detroit, Michigan, experienced record-breaking heat and humidity in the summer of 1995. In mid-July 1995, a period of high relative humidity occurred in the Collection Resource Center collection storage area. Various circumstances delayed the discovery of this high RH: the building engineer was out on sick leave; there was a malfunction in the mechanical system; the recording hygrothermographs were out of calibration; there was no environmental monitoring due to staff vacations. It is possible the relative humidity reached 80–90%. Unobserved, active mold growth began on artifacts in the storage area. It was discovered by staff in early August. Following the discovery, the curator of museum programs contacted a contract textile conservator on August 8, 1995.

On August 9, 1995, the contract textile conservator and the curator of museum programs made a rapid inspection of the collection storage area. Active mold growth was visible on selected objects such as wooden furniture, upholstered furniture, leather chair seats, and ironing board covers. The most favorable sites appeared to be those with soil, a particular finish, or a suitable pH (Hutchins 1995). Costume with high moisture regain, such as wool, showed mold growth on sleeves, shoulders, and trouser creases. Leather and basketry evidenced active mold growth. Spot checks of storage boxes showed that materials in buffered microclimates were less likely to have mold growth. None of the storage boxes containing Tyvek wrappers showed mold growth. Shoes in boxes with the lids closed were free of visible mold. Shoes on open shelving or those in partially opened boxes had active mold growth. The temperature in the storage areas was 65F and the relative humidity 72–75% at the time of the inspection.

The staff had installed one mobile dehumidifier. Budget and procurement problems made it impossible to install more dehumidifiers at this stage (Hutchins 1995). The curator and conservator observed that there were pockets of still air in the storage area. No fans could be placed in the stagnant air pockets as there were no large floor fans available in the Detroit area stores due to the hot and humid weather the city was experiencing.

Representative photographs of the storage area were taken. A log was started to record daily mitigation activity and temperature and relative humidity. Two recording hygrothermographs were activated, and some noncollection hygroscopic materials were removed from the storage area. A short-term hazard mitigation conservator was contracted, and procedures for hiring a full-time project conservator were begun (Hutchins 1995).

On August 23, 1995, a second collection and storage area assessment was made by the hazard mitigation conservation specialist now on-site. With two dehumidifiers running, the relative humidity was in the 60% range, 10% lower than on August 9. The environment was being monitored with the use of five recording hygrothermographs.

It appeared that the active mold growth was diminished. However, mold mycelium was evident on almost every surface, including costume, textile, leather, polished and unpolished wood, basketry, metal, and mixed media (Roberts 1995).

The mitigation specialist conservator took swab samples of the mold from 12 storage area sites including individual artifacts, walls, ductwork, and ceiling. Two sets of samples were analyzed in Detroit by Biological Research Solutions Inc., and cultured on corn meal agar and Sabouraud dextrose agar for five or more days at 25C. Several different genera of mold were found (Appendix 1) including two species of Penicillium, two species of Aspergillus including Aspergillus niger, two species of dimorphic yeast, and the genera Chaetomium and Cladosporium. No quantitative analysis was done. No species identification was established, except for Aspergillus niger.

The genus Penicillium is probably the most ubiquitous fungus and is found in almost every possible environment. There have been cases of human infection attributed to this genus, but many times it has later been determined that the presence of Penicillium in the infected person was not involved in the causation of disease. Cladosporium is a frequent contaminant of industrial systems but is not considered a significant hazard to humans. Some dimorphic yeast and Aspergillus are known to be involved in human respiratory infections. The most serious contaminant identified is Chaetomium. The members of this genus are cellulolytic and are involved in the active degradation of paper and wood (Wireman 1995).

With the molds in the collection area identified as nontoxic irritants and possible allergens, health and safety protocols were established. As the relative humidity in the collection storage area came down to 60%, the active mold growth was arrested. The dormant mold brushed away easily with a dry brush. If the mold growth were active, the mycelium would have smeared when brushed and the artifact substrate would have been vulnerable to mechanical damage (Price 1994).

The objective of the urgent response project was to leave the collection in stable condition, suitable for long-term storage if necessary, but with enhanced accessibility (Dicus 1997).