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Re: [BKARTS] methycellulose stuff



I usually order my methylcellulose from Fisher, though the type I
use( METHOCEL A), is made by Dow Chemical Co. and is probably
available many ways, and I have heard FLUKA is cheaper.  From my old
notes  given at a Cathy Baker Adhesives ands Sizing class I thought
I'd condense a few bits of info that has been useful to me:   Dow
makes(or did when my notes were given) METHOCEL A, then METHOCEL  E,
F, J, and K which are  actually hydroxypropylmethylcelluose.  All are
soluble and reversible in water only, and are class A materials,
tested and stable and ok for conservation, though it seems like
METHOCEL A is most typical in conservation.  The length of the
polymer chains is different, and it is good to know what you need
before ordering, as Bill Minter pointed out!  The chain length is
measured in "viscosity grade" or centipoises.  The longest chains
make better adhesives, which it the way I generally use
methylcellulose, so I order METHOCEL A 4M, which has 4000 centipoises
average chain length.  You can also buy  METHOCEL A 15C, 4C and 15,
with 15 forming the shortest chain, so more likely to stay inside the
paper when used as an  internal size than the longer chain, depending
somewhat on how the paper is dried.

There is such a bewildering array of products to chose from that are
some form of cellulose ether, and they can be pharmaceutical grade,
food grade, and technical/industrial grade with many different
viscosity types.  Then you can also  prepare them in different
solution strengths when you mix them with water!(or other solvents)
So its useful to experiment before using a new methylcellulose
product, and find out as much as possible about it.  I have been told
that for conservation, pharmaceutical grade is best, and food grade
is acceptable, and the industrial or technical grade is not
recommended.

I like using a 2.5 solution of the 4M ...it is sort of a very heavy
cream texture...yum.
--
Consuela Metzger
Lecturer - Book Conservation
School of Information
The Kilgarlin Center for Preservation of the Cultural Record
The University of Texas at Austin
1 University Station D7000
Austin, TX 78712-0390
(512) 471-8293
(512) 471-8285 (fax)
chela@xxxxxxxxxxxxxxxxxx

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