Nevember &, 1960

Dr. E. WM. Kratz, Vice President
Hene-S0! Corperation

NOT County Line Road

Gary, Indiana

Dear BDector Kratz:

My hearty thanks fer yeur letter ef Nevember 3 and for the accompanying
Information and samples. We are ooking at the semples yeu furnished to get
a better Idea of thelr appliceblilty te eur requirements. This will take some
time and | will give you further Information when cur preliminary tests have
been completed.

Off hand, the optical PVA fila seems the most promising and | would
appreciate mere Information on the forms In which you can conveniently furnish
this. Fer further work, It would sult us te heve a roll about one Inch In
width end perhaps a few hundred feet in length. If your siltting equipment
is set up for narrower widths, we could also conveniently use a simi larlength
of one-quarter Inch tape. 1 have ne idea whether you can afford te quote this
Item at a poundage rate comparable to that for larger quantities of PVA film;
If S10 will take care of It, please ship It on the basis ef this letter and
bITT me directly; otherwise, we will precess a routine purchase order.

The critical questions from eur point of view are (1) the transparency of
the film in the ultraviolet (2) the perfection of the surfece and Its freedom
frem scratches (3) the facility with which the film will take up small quantities
of water, for example, as a mist, te give a tacky surface on which dust will
become embedded; this should then dry down to restore the glassy finish of the
dry film and be sultable for micrescepic ebservation. | would guess that the
higher viscesity PVA filas weuld be mest sultable for the purpose.

There is another wey In which PVA might be quite useful fer microblological
studies, one which might have fairly wide epplication. Can PVA be made to: form
filaments which can then be compacted to form a filter to remeve dust from alr
passing through 1t? The adventage of this type of filter would be that the
addition of weter In small amounts would dissolve the filter, release the dust,
and then this weuld become trapped fer ready observation in a transparent glassy
film as the weter evaporated. in ether applications, additional water would be
added to soluabiize the water completely and the dust col lected by sedimentation
or other means, fer further examination and analysis. For the latter procedure
other types of fiber, for exemple, calcium algenate and gellatin foam have been
used but | am not sure they ere as satisfactory as PVA ought to be If properly
compounded and developed for this line of applications. A related use of PVA
filament material would be In the fabrication of swabs and other sampling pads,
etc. that would be quite useful in beth hospital and research laboratory
applications.

Yours sincerely,

Joshua Lederberg
Professor of Genetics