Page | 1 Susan Richardson Art Conservation 301 Dr. Vicki Cassman

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Susan Richardson
Art Conservation 301
Dr. Vicki Cassman
October 15, 2009
HOBO 13, University Archives
Overall Situation
HOBO 13 is located at the final of several cabinets in the University Archives. It is in a
basement, outside of the vaults, and is thus no more climate controlled than the rest of the
building. The cabinet is made of wood and chipboard, is raised several inches above the ground,
and its top is made of chicken wire. It contains many paintings, mostly framed in wood or metal,
as well as a few cardboard boxes containing artwork and documents.
The presence of cardboard, chipboard and wood in close proximity to objects could be
problematic. In this case, the potential damage is fairly minimal because the surfaces of the
paintings do not come in contact with the wood. The frames are generally made of wood, and
contact with lignins should not cause any damage to the frames. However, if the surface of the
paintings were to come into contact with the wood, it could cause damage.
Several pipes run directly above the cabinet, including chilled water pipes. Within the
climate-controlled vault, there has been no problem with condensation on the pipes. The hall is
more prone to fluctuations in temperature and relative humidity than a climate-controlled vault
would be, so this does not mean there is no risk for the collections in HOBO 13. The presence of
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the pipes also creates the potential for an emergency situation: leakage, or even bursting, are
possible and would be disastrous for the contents beneath. Although the cabinet is raised off the
ground, this doesn't provide any protection from water coming from above.
There are some dust bunnies and insect husks outside the cabinet, and there is a known
cricket problem in the archives. There are several glue traps laid around the archives for
monitoring, but there are none in proximity to HOBO 13.
Strategies

Switch out the interleaving cardboard with acid free mat board or blue board.

Line the shelves with some form of archival material such as cotton muslin or tyvek.

Cover the top of the cabinet with waterproof plastic, preferably an archival polyethylene.

Place a glue trap near or inside the cabinet to test for insect presence.
Temperature and Relative Humidity
Since HOBO 13 is located outside of the climate controlled vault, it is unsurprising that it
exhibits great variation of climate. On the whole, it detected wide swings in humidity
throughout the year. It was wettest in the summer and early autumn months, and driest in late
autumn and early winter. Although a certain amount of fluctuation is acceptable, in this case the
detected relative humidity percent went from 15% or lower up very near to 80%. A 65% or
greater swing in humidity is dangerous. Such a dramatic change in relative humidity, even over
the span of several months, has potential for severe damage to collections.
Temperature fluctuated seasonally, ranging from the low 70s to the low 80s.
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The Archives are located in a heavy masonry building with double-glazed windows, an
ASHRAE class IV building. Thus, a control level of B (50% ±10% RH, and 77±9 degrees
Fahrenheit) should be possible with the building envelope, but may not be practical without an
overhaul of the HVAC system to provide a more nuanced response during the highly variable
spring and autumn months. At the moment, temperature is within a very reasonable range, but
relative humidity is wildly variable, placing the current control level at D (<75% RH). With the
current HVAC system, it should be possible to improve the situation to C (25-85% RH,
temperatures usually below 77). Although C is not ideal, any improvement is good.
For the sake of ease, the relevant charts and conclusions will be presented by season.
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Autumn
Temperature
Mean
Range
Minimum
Maximum
Relative Humidity
77.2950016
6.819
74.271
81.09
Mean
Range
Minimum
Maximum
40.99982143
61.53
15
76.53
Autumn was the season with the greatest fluctuation in Relative Humidity. During
Autumn, both the highest and the lowest percent relative humidity were recorded. There is an
overall range of 61.53 between the highest and lowest reading, which is astounding.
Highest Humidity
The highest relative humidity on record for Autumn was 76.53% on September 6th at
5:15 PM. The temperature at that time was 80.029 degrees Fahrenheit.
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Looking at the Dewpoint calculator, it becomes immediately clear how harmful such a
high level of humidity can be. Every category is in the red. At this level of humidity, all objects
are at risk. Metal objects may corrode, and organic objects may grow mold in a manner of days.
Objects sensitive to humidity, such as wood or fabrics, may expand, and chemical aging will
occur in ten years.
Fortunately, this level of humidity only really occurred on a single day. Unfortunately,
such a rapid and dramatic spike in humidity has its own associated risks. Rapidly changing
humidity can cause wood to warp, splinter or crack and can cause paint cracking due to
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expanding and contracting canvas. Since many of the paintings around HOBO 13 are framed in
wood, have wooden stretchers or are painted on canvas, this is an area of concern.
Lowest Humidity
The lowest relative humidity recorded in Autumn was 15%, on November 22th 2008 at
1:00 PM. The temperature at the time was 76.703 degrees Fahrenheit.
At first blush, humidity this low appears to be relatively harmess. Two of the four
indicators are in the green. There is little risk of mold growth or metal corrosion, and chemical
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aging of objects is reduced. However, at such a low humidity level, organic objects grow weak
and brittle. It wouldn't be good for a collection to remain at such a low humidity level for long.
Strategies

Increase interleaving material between paintings to buffer against humidity swings.
o Cardboard works fine for this, so long as it remains in contact with only the
wooden frame of a painting and not the painted surface. Otherwise, use archival
blue board or acid-free mat board.

Run a dehumidifier in early Autumn.
o Any dehumidifier used should have a humidistat set to 50% relative humidity. If
not, since early Autumn runs from moderately humid to very humid, there is little
risk of overdrying the air.

Run a humidifier in late Autumn.
o Any humidifier used must have a humidistat set to 50% relative humidity.
Otherwise, it is not worthwhile, as humidity fluctuates so much throughout late
Autumn. Trading risk of mechanical damage for risk of mold growth isn't much
of an improvement.

Lower temperature in area to raise Relative Humidity in late Autumn.
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Winter
Temperature
Mean
Range
Minimum
Maximum
Relative Humidity
76.60718009
6.264
73.062
79.326
Mean
Range
Minimum
Maximum
24.39085764
31.2
15
46.2
Winter was a fairly stable season in terms of humidity. Although there was much
variance from day to day, the overall range between high and low was 31.2: less than half that of
Autumn. Humidity was never riskily high, although it did dip riskily low at several points during
the winter, and in fact spent a large portion of the time at or below the sensitivity level of the
hobo (15% RH).
Highest Humidity
The highest humidity recorded in Winter was 46.2% on February 17th, 2008 at 10:30
AM. The temperature at the time was 76.876 degrees Fahrenheit.
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The humidity was sufficiently high to be a slight risk to organic objects, with a PI of 27
years. There was little risk of wood cracking or splitting, and there was no chance at all of mold
growth. Humidity never spiked above 50% during the winter. However, there were rapid shifts
of around 20% in a single day, which is dangerous in and of itself.
Lowest Humidity
The lowest humidity recorded in Winter was 15%, several times throughout the season.
This is the lowest that this particular type of HOBO can detect, so it might well have been lower.
The average temperature for the season was 76.61 degrees Fahrenheit.
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See Lowest Humidity analysis for Autumn, as the results are the same.
Strategies

Increase interleaving material between paintings to buffer against humidity swings.

Run a humidifier throughout the winter.

Lower heat in archives area, to increase relative humidity.
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Spring
Temperature
Mean
Range
Minimum
Maximum
Relative Humidity
75.21550521
7.488
72.718
80.206
Mean
Range
Minimum
Maximum
37.09192482
50
15
65
Spring was almost as bad as Autumn in terms of fluctuating humidity. It had a large
range of 50 between high and low, and there were significant changes in humidity over the span
of a few days.
Highest Humidity
The highest humidity recorded in Spring was 65% on May 25th, 2009 at 8:30 AM. The
temperature at that time was 77.749 degrees Fahrenheit.
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Although there is no risk of mold growth, metal and organic objects are both at risk of
damage at this humidity. Worse yet, the humidity is significantly lower earlier in the day.
Temporary spikes in humidity can be extremely damaging.
Lowest Humidity
The lowest humidity in Spring was 15% or lower, and was recorded on several occasions.
The average temperature was 75.22 degrees Fahrenheit.
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The risks are identical to those of Winter and Autumn's lowest humidity days.
Strategies

Increase interleaving material between paintings to buffer against humidity swings.

Run a humidifier in early Spring.

Lower heat in early Spring to raise Relative Humidity.
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Summer
Temperature
Mean
Range
Minimum
Maximum
Relative Humidity
76.49599502
9.189
70.137
79.326
Mean
Range
Minimum
Maximum
56.69838315
31.13
42.03
73.16
Summer had a fairly stable level of humidity. However, overall the humidity level was
quite high. It was the only season not to have dangerously low humidity levels, but all but a
handful of days had relative humidity over 50%.
Highest Humidity
The highest humidity recorded during the summer was 73.16%, on June 13, 2009 at 3:30
PM. At that time, the temperature was 70.651 degrees Fahrenheit.
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The potential for damage to all collection objects is high at this temperature and relative
humidity. All of the indicators are in the red. There is a significant chance of metal eroding, of
organic objects experiencing chemical aging, and mold growing. Although most days in summer
weren't as humid, the overall humidity during summer merits concern.
Lowest Humidity
The lowest humidity recorded during the Summer was 42.09% on June 1st, 2009 at 3:45
AM. The temperature at that time was 74.619 degrees Fahrenheit.
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This temperature and relative humidity are decent. There is still some risk of chemical
aging, but the risks of mechanical damage and metal corrosion are low, and the risk of mold
growth is nonexistent. Ideally, humidity during the summer should remain at around this level.
Unfortunately, there is only one day where the area around HOBO 13 is this dry.
Strategies

Run a dehumidifier throughout the Summer.

Check collections for signs of mold growth.
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