UCLA/Getty Conservation Program

A graduate conservation training program focusing on the conservation of archaeological and ethnographic materials


A second start: A suction table treatment of a basket start affected by mold

As part of our class “Conservation and Ethnography”, each student worked on an object from the Agua Caliente Cultural Museum (Palm Springs, CA).  I worked on a Kumeyaay coiled basketry start owned by a private collector in Palm Springs that had mold growing on both sides of the object.

The Kumeyaay are located at what is now the border between the United States and Mexico, along the Pacific coast. This coiled start has thirteen coils and the beginnings of a spiral pattern, all made out of juncus. The five-part spiral pattern was created through the introduction of the red portion of the juncus stems.

Front of basket start before treatment

Back of basket start before treatment

Mold developed on the object due to a combination of a source of moisture and cycles in temperature. Molds can damage the surface and structure of individual objects and can spread from object to object within a collection. Therefore, this object was treated to remove the mold in order to prevent further damage to the object as well as to prevent the mold from spreading.

The mold was located on both the front and back surface of the object affecting both the epidermis and the cuticle of the fiber and possibly causing darkening of cracks. The presence of mold on both sides of the object suggests that it was also present within the object itself. The mold covered approximately one third to one half of each of the object’s faces.

Preventive Conservation and Vacuuming

The treatment of the object began with preventive conservation measures. The basket start was placed on a tray in two polyethylene bags with a desiccant. The tray was designed to be somewhat rigid to prevent any mechanical damage to the brittle plant material during handling while in cold storage. The silica gel desiccant was placed in polyethylene bags with cheese-cloth windows. The object was then placed in the freezer to prevent new mold growth. The removal of moisture from the object and the reduction of temperature prevented the continued growth of the mold.

The object on its tray in a polyethylene bag with the silica gel and a cobalt RH indicating strip

Dessicant packet

Once the moisture from the mold was removed and the mold could be brushed without smearing, it was removed by vacuuming with a high efficiency particulate air (HEPA) vacuum. The nozzle of the vacuum was covered with a fine mesh cloth to prevent any loose fragments of the basket from being vacuumed up. A brush was used to dislodge the mold and guide it to the vacuum nozzle.

Vacuuming the basket with a HEPA vacuum and a brush

Detail of the mold

During treatment, to protect against the mold spreading, surfaces were covered with tissue paper. When possible treatment occurred within a fume hood or with a fume extractor nearby, while also wearing goggles, a respirator with a particulate filter, gloves and a lab coat. At the end of each day, the tissue paper was folded up and disposed.  The tools were cleaned and the area wiped down with ethanol with 20% water (Florian, 2000, Guild and MacDonald, 2004:20-21).

The Suction Table Treatment

In order to fully clean the object and reduce the chance that the mold would begin to grow again on the object, the object was cleaned with ethanol with 20% water on a suction table (alt. solvent trap or suction disk). The suction table treatment was chose because it would pull the ethanol solution through the object, guaranteeing that the solution would penetrate the interior of the object and kill any mold present within.

Diagram of the suction table (Image modified from Stiber and O’Loughlin, 1992)

Suction tables are like flat vacuums and exert suction on the materials placed on them. The vacuum creates a pull in the Erlenmeyer flask, which pulls at the air through the filter. The water in the flask traps the mold and prevents it from entering the vacuum. The filter paper helps to pull the solvent down and away from the object (Hackney and Fairbrass, 1980, Michalski, 1984, Varga, 2007, Vitale, 1988, Weidner, 1984).

The suction table created for this treatment had a perforated metal sheet over the funnel opening to provide support to the object and filter paper while still permitting air to pass through (Katz, 1999).  The manufacturer of the Cast-N-Vac pump (vacuum pressure: 26 Hg) used for this suction table was contacted and to confirm that ethanol could be used safely with the machine.

Suction table

Before applying any solution to the object, spot tests were carried out to ensure that it would not adversely affect the object. Then, the object was placed on the suction table and the ethanol with 20% water solution was applied by pipette to the area over the opening in the table. Enough solvent was applied to pass through the object and appear on the filter paper below. After the vacuum had had a chance to pull most of the solvent through, the object was moved so that another section was over the suction opening and the process began again.

Following treatment, the object was placed in a bag with several packets of a desiccant. The packets of desiccant were refreshed when they changed color, indicating they had reached saturation. The removal of the moisture introduced during treatment was important to prevent the growth of any new or remaining mold spores on the object. Several days after treatment, the object was examined under a microscope to look for any remaining mold spores. None were found and therefore it seems likely that the suction table treatment removed the mold.

Additionally, the filter papers used to test and conduct the suction table treatment were photographed in normal and UV light. These were then compared with an unused blank filter paper and a filter paper that had had the ethanol and water mixture applied to it. The test and treatment filter papers fluoresce and the unused filter papers do not. This suggests that something was removed during the treatment. You can also see that the treatment filter paper is slightly yellowed. This may indicate that some components of the plant materials may have been solubilized by the ethanol-water solution and transferred to the filter paper or the fluorescing material could be related to the mold.

Filter papers viewed with diffuse light and UV induced visible fluorescence

The most effective and efficient method of mold prevention is maintaining good climate conditions. For mold prevention, this means keeping the relative humidity below 65%. For storage collections, increasing air circulation can also help to reduce mold growth by ensuring that no localized areas of high relative humidity develop. For this object, a box was made to facilitate the maintenance of a dry microclimate and prevent future outbreaks of mold.

Basket start after treatment

Treatment Materials
Buehler Ltd.
41 Waukegan Road, P.O. Box 1
Lake Bluff, Illinois 60044-1699 USA

Dessicating Silica Gel, Item # MS03/O
Conservation Resources International, LLC
5532 Port Royal Road, Springfield, Virginia, 22151

The silica gel used in this treatment maintains a very low relative humidity. It can be refreshed by removing the silica gel from the bag and placing it in the oven until it turns orange. It can then be cooled and placed back inside the packet.

Works Cited

Florian, MLE. 2000. Aseptic technique: a goal to strive for in collection recovery of moldy archival materials and artifacts. Journal of the American Institute for Conservation 38 (1):107-15.

Guild, S, and M MacDonald. 2004. Mould Prevention and Collection Recovery: Guidelines for Heritage Collections. Vol. 26, Technical Bulletin. Ottawa: Canadian Conservation Institute.

Hackney, S, and S Fairbrass. 1980. A High Vacuum Suction System for the Removal of Stains on Paper. The Conservator 4:1-4.

Katz, K. 1999. An Inexpensive Mini-Suction Table. AIC Paintings Specialty Group Postprints, edited by F. Wallace. American Institute for Conservation 27th Annual Meeting, St. Louis, Missouri. Washington, D.C.: AIC. 85.

Michalski, S. 1984. The Suction Table: II A Physical Model. AIC Preprints. American Institute for Conservation of Historic and Artistic Works Preprints of the 12th annual meeting, Los Angeles, California. Washington, D.C.: AIC. 102-111

Stiber, Linda and Elissa O’Loughlin. 1992. Hinge, Tape and Adhesive Removal. Chap. 15 in Paper Conservation Catalog. Washington D.C.: American Institute for Conservation Book and Paper Group. www.conservation-wiki.com/index.php?title=BP_Chapter_15_-_Hinge,_Tape_and_Adhesive_Removal (accessed 03/15/2011).

Varga, L. 2007. A Hand-Held Surface Suction Device: Design, Construction and Application. Textile Specialty Group Postprints. American Institute for Conservation 35th Annual Meeting, Denver, Colorado. Washington, D.C.: AIC. 93-106

Vitale, T. 1988. Observations on the Theory, Use and Fabrication of the Fritted Glass Bead, Small Suction Disk Device. The Paper Conservator 12:47-67.

Weidner, Marilyn. 1984. The Suction Table: Ten Year Review of its Development. AIC Preprints. American Institute for Conservation of Historic and Artistic Works Preprints of the 12th annual meeting, Los Angeles, California. Washington, D.C.: AIC. 94-101.

Robin OHern (’12)