During Crista Pack’s 2011 summer project at the Alaska State Museum, she found several artifacts with a strange white mold-like substance on them. Suspiciously, the items were all from the same 2003 accession, but not all the artifacts from that accession had the mold. Baskets and other weapons were fine. And incoming paperwork and photographs indicated there was no issue when they arrived. None of the other artifacts in the drawer had the mold, just a few from this donation. To deepen the mystery, I realized this was similar to a spot of strange white mold that had been previously found on a basket at the Sheldon Jackson Museum in Sitka. We convinced ourselves through microscopy that in spite of proper storage and environmental conditions at both museums, indeed we DID seem to be seeing mold. Yikes!
Careful examination of both the Alaska State Museum and Sheldon Jackson Museum collections failed to turn up any further examples. Crista was determined to get to the bottom of it and pursued the question during her next semester of school at the University of Delaware/ Winterthur graduate training program in conservation. Here is her excellent report on the matter:
After receiving the report, I emailed her a few more questions, and here were her responses:
Ellen: We’ve definitely got mold, maybe a couple different kinds mixed together but some of that possibly due to contamination on the way?
Crista: Yes – the fact that these were the only items in the drawer affected makes me think that these spores came in on the artifacts. Especially if these have just been hanging out in the drawer for the past 6 years. If they’d been on display for any length of time, then that might be a different story. Either way, the molds that were identified are all very typical molds found on things in interior spaces.
Ellen: So, RH alone isn’t the culprit for mold growth, although we tend to focus on it. Temp, nutrients, water content, mold type also matter.
Crista: Yup – RH is much easier to measure than water content, so people tend to focus on it more. Most interesting I thought was that mold does not appear to take water from the air…it takes it through the substrate. So RH will impact the water content of an object…but that is going to vary according to different materials, other environmental factors, etc. etc.
Ellen: Let me get this right…we likely have mold because there were spores already there and the temperature and nutrient conditions were good and the mold type is a kind that has some of its own moisture/ doesn’t need as much moisture to flourish?
Crista: I think so…although I can’t confirm that the mold is specifically the type that doesn’t need as much moisture to flourish – I just wouldn’t rule it out. If it’s not, then the other combination of temp, nutrients and water content of the substrate (and/or dust in crevices) would be more at play.
Basically, I’ve learned that mold is freakishly smart and resourceful…and it has an incredibly strong will to survive. And that regulating RH can help prevent it because water content plays an important role – BUT it is really hard to define a specific RH limit, because each and every situation is going to be unique. I think the current guidlines that most people seem to adopt of keeping spaces below 60% is probably good and prevents a lot of mold from growing…but it’s like birth control… it’s only effective 99% of the time (or so I’m told!). And actually, the RH guidelines might not even be effective 99% of the time…I’d guess more like 92% of the time. 😉 That is my extremely scientific calculation that I’m giving you there..haha!