[NHCOLL-L:802] ethanol tank seals

[Alastair Graham]

A year ago we moved into a new facility specifically designed for our 
fish collection, which contains about 100,000 preserved specimens. 
The bulk of the material is stored in 70% ethanol in jars, drums & 
tanks.  Our new storage area is mechanically ventilated.  However we 
are finding that the ventilation is too effective, as ethanol is 
being drawn off (or evaporated) from the tanks at a rapid rate.  In 
fact we have added over 1300 litres of 70% ethanol to our 25 tanks in 
the last 12 months.  This evaporation rate is concerning, not only 
because of the potential damage to specimens if they dry out, but 
also due to the cost of ethanol.  Our old storage area had a much 
inferior ventilation system, which did not cause evaporation 
problems.  Apparently the old system did not meet the current 
building code standards with regard to flammable liquids.

Our tanks are made from polyethylene.  Their dimensions are 1.4m x 
0.7m & 0.8m high (with a capacity of 450 litres) & 1.2m x 1.2m x 0.8m 
high (with a capacity of 500 litres).  They have a polyethylene lid, 
which sits over the base.

The advice from the ventilation engineer is that it will be 
"expensive or impossible" to reduce the ventilation in our new 
storage area.  So we have to look at modifying the seals on the tanks.

Does anyone have any experience with using rubber or a similar 
product to seal large specimen tanks?  My experience with rubber-like 
tank seals is that they either "bleed" when they are in contact with 
ethanol & this may cause staining of the specimens or the rubber 
becomes soft & sticky over time.  Also, many adhesives used to attach 
rubber to the plastic of the tank (either lid or base) are soluble in 
ethanol.

Thanks in advance for any input.

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Alastair Graham
Fish Collection
& Photographic Index of Australian Fishes (PIAF) Manager

CSIRO Division of Marine Research    Phone: (03) 62 325 222
GPO Box 1538                           International: (61-3) 62 325 222
Hobart  Tas  7001                    Fax:   (03) 62 325 000
AUSTRALIA                              International: (61-3) 62 325 000
                                      E-mail: Alastair.Graham at marine.csiro.au
Division website: http://www.marine.csiro.au
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