Plastic drafting tools

Thomas Braun <Thomas_Braun [at] nps__gov> writes

>Recently, we discovered in our
>collection some historic clear plastic drafting tools that had begun
>to deteriorate...
>The majority of them simply smell bad, something
>akin to old cheese or an acidic vomit-like smell.  Most of them are
>also brittle and have cracks and fractures. A few of them are badly
>crazed and fragile, and crumble into tiny pieces if not handled
>carefully; several were found completely degraded.  We soon began to
>suspect that these tools were made with cellulose nitrate or
>cellulose acetate.

The problems you've encountered with plastic drafting tools are
quite similar to the problems we've encountered in the treatment and
conservation of animation cels over the past 19 years.

We have noted that materials used to manufacture cellulose acetate
products during WWII have an emesis-like fragrance and often present
an oily surface exudate. Overall shrinkage is usually evident with
the surface often beginning to show signs of welts or lesions.

Nitrocellulose exhibits another completely different set of symptoms
and becomes so fragile that it is completely impossible to handle in
its final stages of dissociation.

Acetate is quite frequently mistaken for nitrocellulose and a
positive identification must be made before you undertake any
treatment. Too, freezing may not deliver the results you desire
except to make it impossible for an object made of nitrocellulose to
spontaneously combust.

We have an on-going research project dealing with the issues
surrounding the aging and conservation of cellulose acetate and
nitrocellulose materials. You and any other conservator interested
in our findings, techniques and tests are welcome to contact me
directly.

Ron Stark, Director
S/R Laboratories Animation
Art Conservation Center
818-991-9955

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                  Conservation DistList Instance 9:36
                 Distributed: Sunday, October 22, 1995
                        Message Id: cdl-9-36-006
                                  ***