Cabinet

In response to the discussion of fireproof or fire-resistant safes
and cabinets, it should be noted that *most* of these enclosures use
an intumescent filler between the inner and outer walls.  Such
fillers act as both passive insulator and active cooling agent to
protect the contents from the heat of an external fire.  When
subjected to a fire, these fillers use the heat to convert absorbed
moisture to gas, thereby keeping the contents cool.

Obviously, the fillers have the capacity to absorb and hold
moisture.  The typical result is that interior RH conditions are
maintained at an artificially and deleteriously high level.
Consequently, I recommend that fireproof safes or file cabinets
never be used to store archival material, particularly photographs.
Use uninsulated storage cabinets and fireproof the room with more
conventional insulation and barriers.

It should also be noted that the use of desiccants in a fireproof
cabinet will (if enough desiccant is used) obviate most of the fire
protection offered by the cabinet.  If not dehydrated very
frequently, desiccants such as silica gel will act the same as the
intumescent filler--absorb moisture from the surrounding air and
create a high internal RH.

Fireproof cabinets not only create deleterious environments, but are
quite costly to purchase.  Since they have so little to offer, it
makes sense to use lower-cost conventional storage enclosures and
spend the money saved on fire protection for the room and/or total
structure.

Geoffrey I. Brown
Curator of Conservation
Kelsey Museum
University of Michigan
Ann Arbor, MI
313-647-0439

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                  Conservation DistList Instance 10:96
                    Distributed: Monday, May 5, 1997
                       Message Id: cdl-10-96-001
                                  ***