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Subject: Mold on EVA

Mold on EVA

From: Stuart Welch <stuart.welch<-a>
Date: Wednesday, November 26, 2014
Abigail Bainbridge <bainbridge.abigail<-a t->gmail< . >com> writes

>I have been having EVA from Conservation by Design go mouldy within
>two months lately; they say the supplier has changed the formula and
>they're working on packaging that would eliminate contact with air
>but in the meantime can't guarantee any shelf life at all once it's
>opened. ...

Chris Stavroudis hits the nail right on the head: "This is probably
because the manufacturer has included less preservative in the
formula--perhaps not such a bad thing."

Abigail's question leads me to send information a bit sooner than
intended regarding work I have been doing to develop a second
generation of Evacon R (a CXD trade name) which passes all PAT
(Photographic Activity Tests) and Oddy tests.  This has proved a
lengthy process with work beginning in 2010.  We have Oddy and PAT
tested many variants of EVA (including some examples from
competitors none of which passed all the tests).  Sometime after
starting on this project we began to experience problems of the
adhesive going mouldy.  This was brought about by changes in the
formula to meet current legislation on preservatives.  In order to
counteract this problem of mould we will be using a new type of
packaging for the next generation of Evacon R.

The original formulation of Evacon R (circa 1983) which I instigated
contained a small amount of formaldehyde to preserve it in the wet
state and O-phenyl phenol (OPP) to protect it in the dry state.
These were consciously chosen over biocides because our adhesive
chemist was worried that the sulphur content of the biocides could
react with silver.  We were especially concerned at that time with
silver tarnish from products used in photographic conservation.  The
formaldehyde evaporated when the adhesive dried but was very
efficient in preserving it in the wet state and there are examples
of Evacon R which has lasted for many years.  However, these
preservatives are no longer allowed to be used.

One of the main reasons for changes to the types and amounts of
preservatives in adhesives is their use in food packaging.
Preservatives have also been reduced in the base EVA resin before
the adhesive manufacturer gets it and starts making a specific
formulation.  Since we are not producing an adhesive for food
packaging we might simply compensate for this by adding more
preservative biocides to solve the problem of mould.  However, we
know this would negatively affect PAT tests and Oddy tests.  The
adhesive may also have to be classified as hazardous if certain
limits were exceeded.

I began the programme of redevelopment on behalf of Conservation By
Design for a second generation of Evacon R to try and solve
something that had long troubled me.  Our current Evacon R passes
all the PAT tests and Oddy tests for Copper and Silver, but not
Lead.  I therefore wanted to find a new version that passed all the
above and also passed the Oddy test for Lead.  It had to have a
stable pH of 7 and would not be classed as hazardous.  We were
fortunate and very grateful to have had assistance from the British
Library and Dr. Paul Garside who carried out the Oddy testing for
us.  The PAT testing was done by the Image Permanence Institute,
Rochester Institute of Technology. USA.

I am pleased to announce here that following extensive testing we
now have a new version of Evacon R that ticks all the boxes and will
be available in the new packaging that is designed to reduce the
risk of it becoming mouldy.  We expect this to be available at the
beginning of 2015.

    Oddy, Copper
    Oddy, Silver
    Oddy, Lead
    pH 7

If anyone would like to be contacted when this new version is
available please send your details to sales<-a t->cxdltd< . >com.

Stuart M. Welch
Development Director
Conservation By Design Limited (A Berkshire Hathaway Company)
Timecare Works
5 Singer Way
Bedford MK42 7SL
United Kingdom
Home Office:+44 1234 708 359
Mobile +44 7836 263270
Fax: +44 1234 852334

                  Conservation DistList Instance 28:26
                Distributed: Saturday, November 29, 2014
                       Message Id: cdl-28-26-003
Received on Wednesday, 26 November, 2014

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