Wooden object

Jane Foley <jfcfoley [at] hotmail__com> writes

>I am examining a mechanical museum object which is degrading badly
>in specific areas. It is a 'circus' parade manufactured between the
>1950s and late 1960s. Some parts are wood some are plastic. The wood
>is stable.
>
>The painted plastic objects (moulded horses and people), are
>exhibiting salts on the surface, distortion of the plastic
>substrate, brittleness and extensive paint loss. The two main paint
>colours are red oxide and grey. The exposed metal parts are rusting.

I am sure others will respond about this with more help, but this
may be another case of cellulose nitrate or cellulose acetate
degradation.  If so, it is the plastics themselves which are to
blame and may have nothing to do with the environment, though
elevated humidity will definitely speed up the degradation.  In both
cases, acidic vapors are released causing metal corrosion.  C.N.
Gives off a camphor and acrid nitric acid odor.  C.A. Will give of
an acetic acid/vinegary odor.  Both processes are irreversible and
can only be slowed down by cold storage techniques.

Until tests can be performed to identify the plastics and positively
identify the source of the problem, the object should be isolated
from other collections but allowed to breath to prevent buildup of
acidic vapors.  Lots of buffered tissue can be used to absorb acids
temporarily.

If this is an historically valuable object, it may be ultimately
necessary to disassemble, make replicas of the degraded plastic
parts and put the original parts into permanent cold storage.

Linda S. Roundhill
Art and Antiquities Conservation
18121 157th Ave NE
Woodinville, WA 98072
425-481-0720


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                  Conservation DistList Instance 18:49
                 Distributed: Thursday, April 14, 2005
                       Message Id: cdl-18-49-002
                                  ***