Liquid gate printing

I think that there are some other people who will have views on the idea
of liquid gate printing, however, I'll throw in my 2 cents also.

There are a large number of reasons why the liquid gate method probably
will not be applied to glass plates.

Glass (in my experience) was invented by Murphy (the same person who
gave us Murphy's laws.)  In photographic applications, it is probably
the most pig-headed material invented.  Case in point: when you want
something to stick to glass (such as a photographic emulsion), it
doesn't.  When you don't want it to stick (such as in use as a glazing
material for framed photographs), it does.  Photographic emulsions on
glass whether they are gelatin, collodion or albumen don't tend to stick
very well.  There were 11 design considerations in creating the liquid
gate. Most of these wouldn't apply to glass plates (such as pin
registration and ease of splice passage).  However the one important
point is that film must enter and leave the gate dry.  Solvent is
introduced into the gate under light pressure (about 26 torr or 3.5 kPa)
with the gate and the film under vacuum.  Vacuums are between 101 and
127 torr under atmospheric pressure (13.5 to 16.9 kPa under atmospheric
pressure.) The exiting film is squeegeed using air knives or air
squeegees and solvents removed under vacuum.  Depending on the speed of
the film (the ACME Optical Printer runs at 8 to 16 ft/min), air
pressures of 5 to 60 lb/sq. in are used to remove the solvents.  This
translates to between 3.8 and 46 cubic feet of air per minute (108 to
1300 LPM). The combination of physical forces (especially the
squeegeeing) and solvents may be enough to remove the emulsion right off
of the plate.

You might suggest that the gate be made more open and that wet plates be
allowed to air dry.  However based on the solvents recommended for film,
this suggestion may not be very safe.  Granted the solvent combinations
for glass supported objects will be a little different than for plastic
supported objects, but I'm willing to bet that the toxicities won't be
very different.  At least in 1971, the recommended solvent for film use
was perchloroethylene.  Other solvents or solvent combinations
recommended were Decalin (a mixture of cis- and
trans-decahydronaphthalene), Freon-113, 1,1,1-trichloroethane,
perchloroethane, 1,1,1-trichloroethane/perchloroethane,
Freon-113/perchloroethane, toluene, Freon-113/toluene, and
1,1,1-trichloroethane/toluene.  The mixtures were particularly good
optically since they had "tuneable" refractive indexes with varying
proportions.  However, none of these solvents are things that you would
want in the air.

For still films in general, I don't think anyone is doing this (although
I have heard of someone who copies tintypes, ambrotypes and
Daguerreotypes by putting them in a tray of water (ack!).  I would not
recommend using the liquid gate for any historical materials.

For more information on the the method I can suggest the following
articles:

R. H. DeMoulin, P.A. Ripson, Jr. and S.L. Scudder,"Application of a
Liquid Layer on Negative Films to Eliminate Surface Defects in Optical
Printing", JSMPTE, 68: 415-416, June 1959.

H.F. Ott, "Liquid Gate for Optical Printing", JSMPTE, 79: 333-337, April
1970.

J.G. Stott, G.E. Cummins, and H.E. Breton, "Printing Motion Picture
Films Immersed in a Liquid, Part I: Contact Printing", JSMPTE, 66:
607-612, October 1957.

J.R. Turner, D.E. Grant, and H.E. Breton, "Printing Motion Picture Films
Immersed in a Liquid, Part II: Optical Printing", JSMPTE, 66: 612-615,
October 1957.

D.A. Delwiche, J.D. Clifford and W.R. Weller, "Printing Motion Picture
Films Immersed in a Liquid, Part III: Evaluation of Liquids", JSMPTE,
67: 678-686, October 1958.

-Doug

    <"By definition, when you are investigating the unknown, you do not
    know what you will find or even when you have found it." -
    Bassagordian's Basic Principle and Ultimate Axiom>

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                   Conservation DistList Instance 5:4
                   Distributed: Sunday, June 9, 1991
                        Message Id: cdl-5-4-004
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