Smoke machines

Helle Strehle <hs<-at->moesgaardmuseum<.>dk> writes

Monona Rossol <actsnyc<-at->cs<.>com> writes

Thanks in advance,>
>>I would worry more about exposing museum-goers.
>>...
>
>...  Our
>exhibition team is contemplating a product which they claim "leave
>no film on objects".  The product in question is called MDG Neutral
>Fluid and is served by MDG Fog Generators.  The Safety Sheet does
>not inform about the content, but gives the numbers EF 232-455-8 and
>CAS 8042-47-5.  To my knowledge, this could fit on paraffin oil?
>Concerned about people and museum objects: Do we have an opinion
>about this (or similar) products? ...

In general, I would worry that any kind of organic mist or oil risks
leaving deposits, which could attract dirt and pollutants, and/or
chemically interact with surfaces.

Dry ice (CO2 ice) would be an exception to this.  Dry ice works by
dropping the air temperature below the dew point and creating actual
water mist.  Other than the immediate effects upon temperature and
rH (which would be deleterious to museum objects), there would be no
residual effects from this kind of mist, as the water droplets would
just disappear as soon as the air temperature returned to normal.
However, there might also be health and safety issues about having
high CO2 levels in enclosed spaces, if ventilation is inadequate.
Other cryogenic materials could be used, but would be much more
expensive, have other risks (liquid nitrogen has frost burn risks if
it spills, liquid oxygen is explosively flammable as well...), and
would have the same issue of impacts on rH and T.

In theory, if an organic mist with a high enough vapour pressure was
used, the droplets would evaporate quickly enough to not leave
deposits on surfaces.  However, the more quickly a compound
evaporates, the less likely it is to form a mist that hangs around
in the air.  Not only that, but compounds like this (low molecular
weight organic liquids) are more likely to be solvents with chemical
effects, more likely to be smelly, and are likely to affect human
health as well as affect artefact surfaces.

If you go the other direction with vapour pressure and use fine
solid particulates in the air, then that is a dust problem as well
as a health problem.

If dry ice is not acceptable, then I think you need to question how
much you need to have actual mists in your display.  Could you not
use other optical effects?  Maybe fancy lighting techniques to get a
similar impression?

Sorry to rain on your parade (or mist on it).

Valerie Tomlinson
Conservator
Auckland War Memorial Museum
Tamaki Paenga Hira
The Domain
Private Bag 92018
Victoria Street West
Auckland 1142
New Zealand
+64 9 306 7070 ext 7304


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                  Conservation DistList Instance 29:44
                   Distributed: Friday, April 8, 2016
                       Message Id: cdl-29-44-001
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