Deltathor

Valerie Tomlinson <vtomlinson [at] aucklandmuseum__com> writes

>Wouldn't heat treatment be simpler? I've forgotten if this idea was
>mentioned earlier in the string and discarded.
>
>A tight seal would not be necessary, and so long as all materials on
>the carriage could handle 60 deg. C for a few hours it would be OK.
>Just blow hot air into the carriage with doors and windows closed
>until all the beasties are baked. A few heaters with a controlling
>thermostat and a few strategically placed temperature monitors to
>make sure the heat penetration is complete is all that's required.
>
>High temperatures are not ideal for aging of materials but heat
>treatment is fast, so they only have to handle it for a short while.
>Also, one would have to be especially careful with synthetics that
>melt/soften/warp.

Valerie brings an interesting perspective, as heat treatment is a
simple and underused insect control method. However, in this
situation, I think the problem is not merely one of method, but of
scale. How do you ramp up any treatment to be both safe and
effective on something as big as a railway coach? What fascinates me
are the dramatic changes needed in treatment method and scope as
size parameters are modified. This is at the heart of microclimate
environmental control of all sorts.

For example, if you are considering heat treatment as an option, you
need to ask: How much heat energy will you need and how will you
produce it? How will you keep the heat even and avoid dangerous "hot
spots"? How long will it take to achieve killing temperatures? How
can you monitor, humidify (and then dehumidify) the air to avoid
damaging humidity sensitive materials? How will you monitor to
determine that have reached an effective temperature throughout the
car? All fascinating questions, of course, and none of them
especially difficult to determine or calculate, but again, the
difficulty and effects of scaling up and down from a smaller model
could be surprising.

There has been some fairly extensive work on heat treatment and
museum objects, and the companies that offer this process
commercially (all European-based, to my knowledge) have both
theoretical answers and practical experience, but I assure you that
while possible to do an entire railway car interior, it will not
simple, nor inexpensive.

I still think that CO2, with its challenges, is the easiest way to
effect an in-house, "poison free" solution on such a large object.
CO2 fumigation (I don't consider it to be anoxia) avoids many of the
more complex problems presented in heat treatments, seems inherently
safer for artefacts, and promises fewer nasty surprises that might
unnerve an insurance company (or administrator with a limited sense
of adventure).

Jerry Shiner
Keepsafe Microclimate Systems
+1 800 683 4696


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                  Conservation DistList Instance 26:39
                 Distributed: Monday, February 25, 2013
                       Message Id: cdl-26-39-004
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