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Subject: Laropal K-80

Laropal K-80

From: Dennis Baltuskonis <dab.conservation<-a>
Date: Tuesday, February 5, 2008
I have two important questions related to the commercial resin known
as Laropal K-80 (formerly called Ketone-N resin).

Laropal K-80 is a "homo-polymer", the product of a chemical
condensation of cyclohexanone with itself (MSDS sheet).  It is/has
been used as a final varnish for old master paintings and more
importantly represents approximately 30% by weight of the adhesive
formulation known as "BEVA-371".

Does anyone know of a commercial source for this resin?  The German
chemical company BASF has stopped producing this resin and despite
several objections and pleadings from conservators does NOT plan on
resuming production.  Thus far I have been unable to locate an
alternate commercial source.

Do we have a Plan-B?  I am soliciting comments here because I assume
that if there really is no alternative source for this resin it
would mean that in a very short while there would also be no
BEVA-371 (at least not without using a substitute resin,etc.).
Playing this scenario out further... What would that substitute
resin be?  Would the manufacturer even advise conservators about
such a substitute?

This has already happened.  The original BEVA-371 employed a small
amount (approximately 4% by weight) of a "tackifying resin" known as
Cellolyn-21. The Hercules chemical company subsequently discontinued
Cellolyn-21, replacing it with a product called Cellolyn-121.  Mr
Berger stated in his 70's formulation paper that this resin could be
ommitted from the BEVA formula.  I have no idea if the commercial
BEVA-371 contains or does not contain this minor component.

On the other hand, if one were forced to use a substitute for
Laropal K-80, (being approximately 30% by weight of the adhesive
formula), then I would expect that the performance characteristics
of such an adhesive might be significantly different.  Either way,
how could we justify using a product without extensive testing?

For the sake of keeping this posting short, I will stop here.  To my
mind the sudden unavailability of the commercial resin Laropal K-80
will have a major impact on our field, paintings conservators
especially.  It is possible to synthesize small batches of this
polymer but the increase in production cost would--the word
"skyrocket" doesn't begin to cover it.

It may be that, after 30 years on the market, the use of synthetic
adhesives such as BEVA-371 have not lived up to their expectations.
This might be a good time and forum to discuss these issues.

Dennis Baltuskonis
Art Conservation Services
1103 Midnight Drive
San Antonio, TX  78260

                  Conservation DistList Instance 21:43
               Distributed: Wednesday, February 13, 2008
                       Message Id: cdl-21-43-016
Received on Tuesday, 5 February, 2008

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