Dust in Museum Exhibits

Bulletin 30, winter 2008  No pdf link on website yet.

We have long known that dust causes damage to artifacts. The basic
information we tell museums about dust includes:

1.      Dust is unsightly and makes your collection look poorly
maintained.
2.      Dust is abrasive on a microscopic scale due to tiny sharp
mineral particles, such as quartz.
3.      Dust contains pollens, skin cells, insect bits, and other
organic matter that feeds biological growth.
4.       Dust can be acidic.
5.       Dust is “hygroscopic,” meaning it attracts water and holds it
against the surface of an object, contributing to staining, corrosion,
and biological growth.

Recent articles have given us a new understanding of the impact of dust
on our collections.  A paper presented at the 2004 conference of the
American Institute for Conservation  described the forces that help dust
stick to surfaces.  One of these forces comes from sticky “exopolymers”
made as a waste product of microbes (mainly bacteria).  Accumulating
dust provides more food for these colonies of microbes, and layer upon
layer of “biofilm” forms, with the bottom layers becoming firmly adhered
to the surface of your artifact.  Spikes in humidity can encourage the
initial growth and speed the growth of biofilms.  Periods of low
humidity after high ones can stress the bacteria, and might cause them
to produce even more sticky exopolymers.  Yet another reason to try to
keep our museum humidity levels stable!

Other recent articles have explored the role of visitors in creating
coarse dust.  Considerable amounts of dust enter the museum on visitors’
clothes and shoes. Visitors are such a direct contributor to dust that
one study showed dust amounts are cut in half for every 3 to 4 feet of
distance between a visitor and an object. Fibrous dust, largely from
clothing, accounts for only about 3% of the dust in exhibits. But since
the particle size is large and visible, fibrous dust contributes
significantly to the appearance of dustiness. This dust tends to be
thickest at eye level. Dust entering on shoes is more concentrated
closer to the entry, and in greater quantity under wet weather
conditions than dry conditions. This kind of dust only rises about 4 or
5 inches off the floor.

Some preventive measures can be taken. Placing objects in cases and
further away from visitor traffic is one solution, of course, but is not
always possible or desirable. Tightly sealed exhibit cases are better
than ones with gaps, but require construction materials that do not
off-gas harmful chemicals like formaldehyde and acid.  Placement of mats
in entryways significantly reduces the amount of dirt brought into the
building on shoes. Vigorous air movement also increases the rate of dust
coverage. Live performances and pathways through exhibits that involve
sharp turns are examples of “dust raising” activities. Air movement from
fans and open windows encourages dust circulation as well. Sometimes
those factors are unavoidable, but strategic decisions can be made,
particularly in relation to artifacts on open display.

Cleaning of collections on exhibit should be scheduled at least once a
year. Objects displayed in the open should be dusted annually. Artifacts
in exhibit cases can be cleaned on a rotating schedule, with a few
exhibit cases cleaned one year and others the next. After a few years,
all cases will be done and the rotation can begin again. It is useful to
have a map of exhibit galleries that can be annotated with notes and
condition reports if needed.

Good housekeeping is divided into two levels of cleaning. Regular
less-skilled cleaning can be done by janitorial staff or untrained
volunteers, including daily vacuuming and regular dusting of furniture.
Specialized cleaning of exhibits requires more skill. HEPA-filtered
vacuums are especially helpful, since they release less dust back into
the air than traditional vacuum cleaners. Closer to collections objects,
vacuums with adjustable suction (such as a Nilfisk vacuum with a
rheostat) are preferable. Dusting techniques that involve rubbing are
abrasive to most surfaces on a microscopic level, and are best avoided
if possible. Most items can be effectively cleaned with a soft
paintbrush, gently fluffing the dust from the surface into the nozzle of
a vacuum cleaner. For fragile surfaces, you may cover the nozzle with
fine nylon netting, such as tulle, secured with a rubber band.  Many a
loose bead or detached fragment has been saved this way, and you will
see sooner if the suction is too strong (hairs pulled from a taxidermy
specimen, for example).  Feather dusters can be helpful, but beware of
any rough quills that could scratch surfaces and be sure to vacuum the
feathers frequently to remove dust.

Glass and plexiglass surfaces are often the first to show dust. The
Sheldon Jackson Museum in Sitka, which has some of the cleanest exhibit
galleries in the state, has found that cleaning glass with paper towels
and a mixture of 1 part white vinegar to 4 parts water is as effective
as any cleaner. Any cleaner should first by applied to a cloth, and then
to the glass or plexi. Fine mist spray can penetrate cracks of exhibit
cases and damage artifacts. Always be careful to let the case air out
before closing because of the acetic acid or ammonia vapors released by
some cleaners.

Plexiglas(r) requires special attention to prevent the plastic from
fogging or scratching. The Alaska State Museum uses specially formulated
commercial Plexiglas(r) cleaners. One product is called Norvus, and is
available on the Internet through vendors such as Amazon.com and Tap
Plastics.  Novus 1 is for cleaning, Novus 2 is for removing fine
scratches, and Novus 3 removes heavy scratches. Apply with a clean
cotton rag.

Good housekeeping is an important part of preventive conservation.
Cleaning also gives you an opportunity to inspect your exhibits for
problems such as bugs or shifted objects. While updating exhibits is
often not in the budget, dusting costs little and freshens up
appearances.

(sidebar)

Five Defenses Against Dusty Exhibits
1. Sealed exhibit cases are the gold standard.
2. Establish regular dusting schedules.
3. Use extra floor mats near doors.
4. Avoid the use of fans and open doors or windows unless absolutely
necessary.
5. Avoid drastic swings in humidity levels.
6.  Shut down the HVAC when cleaning dust out of the vents.

References:

Tarnowski, Amber L., Christopher J. McNamara, Kristen A. Bearce, and
Ralph Mitchell.  “Sticky Microbes and Dust on Objects in Historic
Houses.”  AIC Objects Specialty Group Postprints, Vol. 11, 2004.
 Yoon, Young Hun and Peter Brimblecomb.  “Dust at Febrigg Hall.” The
National Trust View, Issue 32, Summer 2000.

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