November 21, 1960

Mr. E. M. Kratz
Vice President
Meno-~Sol Corporat ion
OT County Line Road
Gary, Indiana

Dear Mr. Kratz:

Thank you for your letter of November 10; | appreciate your taking the time
and trouble to go Into so much detall in giving me this Information.

in fact, the possibility of controlling the surface properties of PVA
by adding moisture are proving to be extremely useful as we continue our
studies. We are spraying, or rather nebulizing water onto precast dried
films and find that this does give us very good entrapment of dust particles
for further processing In the films. it Is very much to our advantage to be
able to contro! the adhesiveness of the PVA In this way. Since we are con-
cerned with microscopic areas, the optical properties of the films after
they have been sprayed and then allowed to dry out are still very satisfactory.
So { belleve that we are still quite close to the type of product that you
are manufacturing at the present time. Somewhat to our surprise, we are
finding that even films that have been Insolubilized by the Incorporation of
hardening agents will still entrap particles In a very satisfactory way and
keep them bound to the film during further processing. So we are very much
encouraged Indeed with the results so far.

| wes disappointed to have your remarks on the Impossibility of producing
water soluble filaments of PVA. | am not at ali clear why this should be the
case - could not, for example, one extrude a PVA solution Into alcohol as one
means of obtaining filaments? In any event, If you can refer me to any people
who are actively Involved In preparing filaments of PVA derivatives, | might
take this up directly with them.

Thank you for your suggestions of methods of casting films which we will
be looking into.

if it Is stl} tn point, may | then resume my Inquiry as to the aval lability
of PVA ribbon In one of your standard formulations, as {| brought up In my last
letter.

Yours sincerely,

Joshua Lederberg
Professor of Genetics