Posts Tagged ‘mold’

The mold was on many different materials of the long weapons: bone, ivory, feather, wood, leather

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!  

This speck of similar-looking mold had been seen earlier on a basket in our museum collection, but in a different city! The long weapons and basket had never been in the same town.

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:

Mold Growth and Prevention in Museum Environments_Research Paper

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!

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Under construction August 2011

1. BACKGROUND

Many kinds of feathers are used on Alaskan artifacts, particularly those of Native manufacture. Most commonly, feathers are seen as appendages on masks or as fletching on hunting tools or weapons.

2. POSSIBLE CAUSES

The most common white stuff we have seen on Alaskan feathers is insect debris (such as cocoons and frass) or mold. This is most often seen in association with feather damage consistent with insects eating the feathers. Pesticides are also a possibility. The Alaska State Museum has hundreds of taxidermy bird mounts that have tested positive for arsenic.  Some of these mounts may close to 100 years old.  Most bird mounts added to the collection since 1970 were preserved with a freeze-drying technique, but these are at risk for insect infestation.

One mysterious case of “white stuff” involves a hunting tool that displays a sticky, branched fibrous-looking mold. The item came into the collection in 2003 in excellent condition, displaying no mold or “white stuff”. The mold appears irregularly on feather fletching, string lashing, leather lashing, bone, ivory and wood parts. Could it be growing from some sort of coating that was sprayed on the artifact?  The most perplexing part of this mystery is that the artifact has been in a controlled collections storage room inside a cabinet with temperature and relative humidity well below what would be expected to support mold growth. We hope to work with intern Crista Pack when she returns to the University of Delaware to investigate the cause of this peculiar “white stuff.”

3. REFERENCES 

4. EXAMPLES IN ALASKA

Under Construction, August 2011

1. BACKGROUND

Shells can refer to various types of hard protective coverings composed primarily of calcium carbonate and comprise the exoskeletons of invertebrates, the outer layer of an egg or other similar specimens commonly found in natural history collections.

2. POSSIBLE CAUSES

The most common cause of white stuff on shell is Byne’s Disease. Is it contagious?? No, Byne’s is not a transmissible or infectious disease and cannot be spread to you or throughout your collection. What it can do is alert you to improper storage conditions.

Byne’s is a chemical reaction that causes the physical breakdown of calcareous (containing calcium carbonate) materials. The phenomenon is named after Loftus St. George Byne, a 19th century British amateur naturalist who described the finding of this condition in shell collections. He mistakenly assumed the condition was caused by some type of bacteria. Subsequent research in the field revealed that the condition was actually due to chemical reactions taking place at the shell surface. Nonetheless, the term Byne’s “disease” stuck and is still in use.

When the calcium carbonate in shells comes into contact with acidic vapors, salts can crystalize on or erupt through the surface of the shell. Acidic vapors can off-gas from certain storage materials – particularly wood-based and certain plastic products. These kinds of materials can produce acetic acid and formic acid gases, which are then dissolved in atmospheric water and combine with calcium carbonate to form calcium acetate and calcium formate salts. Higher humidity creates more atmospheric water and will accelerate the reaction.

The reaction will destroy the surface of the shell and cannot be reversed. However, changing the environmental and storage conditions can stop the reaction from occurring and prevent further loss.

The overall appearance on the surface of a shell may look very similar to mold. It is described as initially appearing as white, rough, chalky, or fuzzy in patches; perhaps with streaks or spots. These are easiest to see on dark and smooth shell surfaces. Though it may look mold-like, microscopic examination will show a structure that looks distinctly crystalline and mineral – not biological. A vinegary smell in the storage area is another clue. Acetic acid (formed when wood breaks down) is also the main component of vinegar and it’s smell indicates the presence of this vapor and the potential for Byne’s “disease.”

At the Alaska State Museum, we tried an experiment to force Byne’s Disease with little success. We gathered mussel, clam, and scallop shell from the beach, cleaned them, and exposed them to fresh oak sawdust. We tried this enclosed at room temperature, in a lab oven, and even added moisture to accelerate the reaction, but after 8 weeks we did not have drastic crystal formation.  This suggested to us that Byne’s disease formation may take a long period of poor storage. One shell, however, did grow a nice mold sample at high humidity!

3. REFERENCES

National Park Service. (2008) “Byne’s “Disease:” How To Recognize, Handle And Store Affected Shells and Related Collections.” Conserve O Gram. August 2008, Number 11/15.

Crista Pack’s notes: Conserve O Grams provide a great model for how to write a concise, informative article that is useful to conservators and non-conservators alike. Topics covered include history, causes, problematic materials, identification, cleaning, and prevention.  “Byne’s disease” can occur in any natural history specimen composed of, or including calcium carbonate. This includes …limestone-based rocks and fossils.” Includes a great Table listing damaging materials that have been used in museum. “Health and Safety Warning: Calcium acetate and calcium formate…are not the same as common table salt (sodium chloride). NEVER taste these salts, even though you may see this recommended in older literature.”  The salt crystals are water-soluble and may be removed with a brief soak or gentle brushing under running water.  Alcohol, boiling, freezing or microwaving, are NOT recommended.  If storage environment is not altered, the process will start again.

Tennent, Norman H. and Thomas Baird. (1985) “The Deterioration of Mollusca Collections: Identification of Shell Efflorescence.” Studies in Conservation Vol.  30 pp.73-85.

Crista Pack’s notes:  Begins by providing definitions for efflorescence, the methods that have been used to analyze them (XRD, IR, TGA and NMR spectroscopy), and provides the chemical formulas for different components.  The authors also discuss the cause of efflorescence formed on shell from exposure to acetic and formic acids (from wood cabinets). Gives a really good overview of methods used for analysis and descriptions for how the efflorescence forms on different types of shells (patterns, similarities between different shells, natural protective coatings that inhibit growth in some areas, etc.).  Provides some interesting discussion on how NaCl (salt) enhances growth – salt from ocean or salt from washing/boiling shells in salt water which was occasionally done. Page 76 contains excellent images of examples. There is a large section dedicated to the technical analysis studies and the data that was acquired from them. This was a little too in-depth for the scope of this project, but would be useful for anyone with access to this kind of analytical equipment and would like a comparison. The conservation section was short, but touches on the pros and cons of cleaning off efflorescence. More could have been said about the potential damage that could occur from removing efflorescence , as well as something – even just a short statement – about ethics of removing original material. Also gives a short statement about the need for safe materials to be used in the storage of artifacts and refers readers to Blackshaw and Daniel’s article “Selecting Safe Materials for use in the display and storage of antiquities.”  Another method for preservation given is coating the shell, however the article unfortunately fails to mention what shells can be coated with.

Wikipedia. “Byne’s disease.” Online: http://en.wikipedia.org/wiki/Byne’s_disease. Accessed June 29, 2011; last modified on 14 November 2010 at 03:52.

Crista Pack’s notes: While all Wikipedia articles have to be taken with a grain of salt, this one is particularly good in its depth of coverage on the topic and easy-to-understand explanation of the deterioration. It also contains a good list of references with links to pdf articles and a number of good images.

4. EXAMPLES IN ALASKA

Under Construction, August 2011

1. BACKGROUND

Alaska Native and non-Native cultures have made extensive use of mammal fur for all manner of clothing, gear, and artwork. And one can hardly enter a museum, airport, or mall anywhere in Alaska without encountering stuffed mounts of iconic Alaskan animals. The website for the Alaska Fur ID Project includes information about the mammals most often used on artifacts in Alaskan collections.

2. POSSIBLE CAUSES

The most common white stuff we have seen on Alaskan taxidermy is arsenic.  Arsenic is one of the more common pesticides found as residue on many types of objects. According to the National Park Service, arsenic compounds were frequently applied during the 18th – 20th centuries in the form of soap mixtures and sprays to preserve biological specimens and ethnographic objects (Conserve O Gram 2/3 2000,1). To identify arsenic, the National Park Service recommends to

“Look for powdery or crystalline deposits at the base of feathers and hairs, around eyes, in or at the base of ears, around mouth or bill, along ventral incision, at base of tail, and on foot pads. On ethnographic objects, inspect crevices and seams where arsenic may have collected. Even if deposits are not evident, all natural history specimens collected and prepared before the 1980s should be tested for the presence of arsenic.” (Conserve O Gram 2/3 2000, 2)

On fur, the most common white materials are associated with insects. Frass, webbing, cocoons, bug parts, shed larval skins and the like are often found in association with hair loss and even holes chewed through the hide. Occasionally there will be small widely spaced hard blobs adhered to the shaft of the hair down toward the skin, and I have been led to believe that those accretions are more likely from bugs that were bothering the furry creature while it was alive.  You may also see adhesives associated with tear repair from the skin side, such as BEVA 371 film and Reemay (a spun bonded synthetic fabric that is thin and web-like).

3. REFERENCES

_____(2010) “Appendix: Common Museum Pesticides” Pesticide Mitigation in Museum Collections: Science in Conservation: Proceedings from the MCI Workshop Series Smithsonian Contributions to Museum Conservation. Smithsonian Institution Scholarly Press Editor: Charola, A. Elena;Koestoer, Robert J. pp. 71-72

National Park Service’s Conserve O Gram on arsenic: http://www.cr.nps.gov/museum/publications/conserveogram/02-03.pdf

4. EXAMPLES IN ALASKA

Under Construction, August 2011

1. BACKGROUND

The Alaska State Museum has many garments and artifacts made of textile from various periods and cultures over the past few centuries. The Tlingit of Southeast Alaska have woven with mountain goat wool and cedar bark for hundreds of years, if not longer. Some items from the Russian period survive.  Military uniforms, various kinds of outdoor gear, quilts, and dolls are common as well.

2. POSSIBLE CAUSES

The most common white stuff we have seen on Alaskan textile or fiber artifacts is insect debris such as cocoons and frass.  Casemaking clothes moths and webbing clothes moths are the biggest threat. Mold and lint are two other common possibilities.

3. REFERENCES

4. EXAMPLES IN ALASKA

Under Construction, August 2011

1. BACKGROUND

Baskets are very common in Alaska, and are often used where ceramics might have been common in other cultures. Typically, baskets are made of plant materials such as spruce root, cedar bark, birch bark, or grasses. Archaeological basketry over 5,000 years old has also been found in waterlogged sites in Southeast Alaska, and several hundred years old on Kodiak Island.

2. POSSIBLE CAUSES

The most common white stuff we have seen on Alaskan baskets are dust, mold, adhesives, paint spatters, insect debris (such as cocoons) and PEG (polyethylene glycol.) Look with a magnifying glass to see how the white stuff is deposited. Powdery-looking spotty deposits may be mold. Dust would likely settle on certain areas that are horizontal, such as the lid if it has one or inside the base. The underside of the base may have accretions from adhesives, labels, or unclean shelves. Baskets were sometimes adhered onto an exhibit shelf in the old days to prevent them from moving with vibration of footsteps. Adhesives and repairs of various kinds have been used on baskets, so white stuff in association with a tear or loss is likely an adhesive. Waterlogged archaeological basketry was most commonly treated with a white glue in the 1960’s and 70’s, but since then polyethylene glycol treatments have been more typical.  Too much high molecular weight PEG (PEG 3350 or PEG 4000 for example) will result in white deposits on the surface.  These are soluble in warm water, and you can test this with a barely-damp cotton swab on the surface.  There was a period of time when “feeding” baskets with oil was a popular maintenance technique. This sometimes appears as white haze on baskets, and may also make them brittle. Haze could also be a pesticide residue. Always be careful to wear gloves…not only are you protecting the baskets from substances on your hands, you are protecting yourself from whatever may be on the basket.

3. REFERENCES

Hartley, Emily. (1978) The Care and Feeding of Baskets. Self-published.

Ellen Carrlee’s notes: Coating mentioned is paraffin oil in mineral spirits, 16% solution, p 29.  The author mentions that the techniques are derived from procedures developed by Bethune Gibson and Carolyn Rose of the Anthropology Conservation Lab of the Smithsonian’s Natural History Museum, and used there around 1974-75.

4. EXAMPLES IN ALASKA (click to enlarge images and see more info)

Conservators at the Alaska State Museum are regularly asked this question:

“What’s that white stuff?”

Disfiguring white stuff on artifacts and artworks can be the result of a wide range of causes. These are referred to by a variety of terms including: efflorescence, bloom, fatty bloom, spue, blushing, chalking, blanching, haze, dust, grime, salts, mold, transferred images, crizzling, sweating and patina. While these terms each refer to specific types of damages and disfigurements, they are often used interchangeably. This may be due to the similar appearance many of them have at first glance. White fuzzy material on an artifact is often assumed to be some type of mold. Sometimes this is the case, but a number of other things can have the same appearance. Staff at the Sheldon Jackson Museum were concerned that Tlingit hide armor was breaking out with mold. Small white fuzzy patches were disfiguring the surface, and the problem seemed to be getting worse. However, upon examination, the white substance was waxy and records indicated a leather dressing treatment was undertaken in the late 1960’s. At the time, leather dressings were a common part of museum practice and believed to benefit leather by aiding flexibility. Over time, the fats can alter and come out of the leather as a bloom or spue, disfiguring the surface. Leather dressings are no longer part of museum conservation practice.

A wooden dish in the Alaska State Museum collection has a fine sugary-looking white deposit inside. Examination and history of the dish reveal the crystals are related to the bowl’s history as a vessel for holding grease or oil. The presence of those crystals is part of the history of the artifact and tells a story.

GETTING STARTED

“What’s that white stuff” is a great question. Does it belong there? Is it hazardous to humans? Is it destroying the artifact? We suggest a systematic approach to the problem.

  1. Identify the material affected. What is your artifact made of? Our INDEX lists artifact materials vulnerable to “white stuff.”
  2. Examine the context and history of the artifact. What was it used for? How was it maintained? Was it dug out of the ground? Has the environment been stable? Has it been on exhibit? Also ask folks who have worked at your museum a long time. These clues may help narrow down possibilities. Write them down.
  3. Characterize the appearance of the white stuff. Is it powdery? Sticky? Flaky? Is it a haze or a crust? Does it appear in a pattern? Use our list of descriptive words below to help you. Write it down. Take a photo for the files.
  4. Consider the typical POSSIBILITIES. For each kind of material, there are certain kinds of white stuff that we have see more than others in Alaskan collections. We try to list these in the INDEX by material.
  5. Test the hypothesis. Make a guess at what you think it is, and if you can remove a little bit, test your theory.

HOW DO I DESCRIBE WHAT I SEE?

Here’s a list of vocabulary words that can help you characterize what you are looking at.  These words, plus a photo, can help others work on solving your mystery. Check GLOSSARY if needed.

airy

branched

chalky

cloudy

crumbly

crusty

crystalline

dotted

dry

fibrous

filmy

foamy

fuzzy

glossy

grainy

greasy

hard

hazy

matte

opaque

powdery

rough

spidery

spotty

sticky

soft

sugary

translucent

HOW CAN I ANALYZE MY WHITE STUFF?

EASY

  1. Magnifying glass and strong light. Look carefully at the surface and try to characterize the appearance. Is it an optical effect from delamination or abrasion? Or is it accumulated on the surface, indicating an accretion or efflorescence?
  2. Does it roll easily on a tipped surface, like tiny dry balls?  You may have insect frass.
  3. Look for patterns on the surface or an explanation for why the white stuff is in some areas and not others. Consider different materials, which side is “up” and if the pattern may be associated with something applied as a liquid.
  4. If you can sample it with a small pointy tool, note how difficult it is to remove. Powdery? Crumbly? Sticky? Smeary?  This is an important clue. Don’t remove it all during sampling, you may want to try again with another idea.
  5. If you have removed a bit of it, try rubbing some of it on a clean glass surface. Does it smear? Or does it stay crumbly/powdery? A smearing substance can indicate the presences of fats or waxes and may indicate the sample is some type of fatty bloom.
  6. Try adding a drop or two of water, enough to cover the sample. Does it dissolve? If so, it may be a water-soluble salt.
  7. With another sample, try adding a drop or two of mineral spirits.  Does it dissolve now?  Perhaps it is something waxy.
  8. If the sample melts with gentle heating, it may be a wax or bloom. Melting can be done over a hotplate, or even with a bit of foil over a candle.

TRICKY:

  1. If you have a binocular microscope, you can see more detail. For example, branching structures of mold may be visible. Crystals may be evident. Bug parts are more obvious under magnification.
  2. If you have a polarized light microscope, you can see even more detail and observe optical properties. Fruiting bodies confirming mold may be present.

HARD:

  1. Various kind of instrumental analysis may be available at larger museums or universities.  For example, an XRF can identify certain heavier elements that point to specific possibilities like metal corrosion, pesticides etc.
  2. If you are equipped to use acids safely, add a couple of drops of HCl. If your sample bubbles vigorously, it may be a carbonate. Maritime accretions and insoluble archaeological salts often bubble with this test.
  3. While some resources may suggest tasting the salt to confirm that is what it is…this is not a good idea and tasting should never be done to identify an unknown substance. The salts forms in Byne’s disease, for example, are not components of common table salt (sodium chloride) and should not be consumed.
  4. Spot testing can help characterize “white stuff” but you must be equipped with a chemistry lab and familiar with laboratory techniques to perform many of these tests. The main museum reference for these tests is:

Odegaard, Nancy, Scott Carroll, and Werner S. Zimmt. (2005) Material Characeterization Tests for Objects of Art and Archaeology.  Second Edition. Archetype Publications Limited. London.