I am currently finishing a project
to develop a workable matrix film emulsion / coater. I have a good emulsion
formula, and related process for coating onto polyester film. I also have
a dye set which transfers readily, and is very brilliant with good light
fastness. The dyes are wet-fast, and do not require any mordant.
Currently, I am working on getting evenly coated 30x40" sheets. I use a
32" slot coater, which is passed over the film. The film is vacuumed down
onto a very flat large aluminum jig plate. As the coater moves over the
film (by motor), the hot gelatin emulsion flows onto the film in a very
even manner. There is a sprayer system under the platen which is used to
quickly chill the plate, causing the emulsion to gel. The sheet is then
hung up in a HEPA filtered laminar air dryer to dry. The process is fairly
simple, and lends itself to small scale film production. Cost of a 30x40"
sheet of Matrix film (materials only) is about $ 8.00.
The emulsion is a very simple silver bromide emulsion. I use a neutral
Kind and Knox gelatin, and I sensitize the emulsion with a small amount of
hypo. The fog level is very low, and the speed is adequate. I coat onto
Dupont Cronar 0.007" polyester film, which is prepared to accept
photographic emulsions. This is available in 45" rolls.
Note: All processes carried out under a sodium safelight.
Use the following formula to make the matrix emulsion:
Sol A:
Water 250 ml
Potassium Bromide 15 g
Gelatine 20 g
Sol B:
Silver Nitrate 10 g
Water 250 ml
1) Emulsification:
Add B to A using a single jet (dripped from a burette above the beaker used
to hold sol A, while stirring slowly. Add over a period of 30 seconds at
a temperature of 70 deg. C (sol A temp 70 deg C, Sol B is at 24 deg C).
When the two solutions are mixed, the silver bromide crystals are formed
immediately. Speed of addition is critical, and controls the speed and
contrast of the emulsion to an extent. Faster additions yield higher
contrast, and a slower emulsion.
2) Ripening
Continue to stir the solution for 30 minutes while heating the mixture back
to 70 Deg. C. Ripening is the time when the crystals grow to size. After
30 minutes, put the container in a refrigerater, and refrigerate for
several hours, until the gelatine has fully gelled.
3) Washing
Remove the gelled emulsion from the container, and cut it into long strips
of about 1/2" cross section. This is called 'noodling'. Wash the noodles
for 1 hour with at least 6 cold water changes. This washes out any
remaining bromide, and by-products / salts.
4) Sensitizing
Drain the noodles fully. Reheat to melt the emulsion. Add 20 g Gelatin
and dissolve at 70 deg. C. When all the gelatine is dissolved, add 50 mg
hypo, and stir for 30 minutes. This step sensitizes the emulsion, and
increases the speed several stops.
5) Final Prep:
Add 2.0 g of Acid Yellow # 23 (tartrazine dye). This is used to absorb
blue light when exposing the matrix film. Filter the emulsion using a
vacuum filter and a coarse filter paper.
6) Coating:
Pour about 250ml into the slot coater while still hot. Make sure the
platen is quite hot to promote even flow. Coat with a .005" slot at about
1" per second. Chill the platen. When the gel is strong, pickup the
sheet and transfer to a HEPA filtered dryer. Dry in low humidity air using
heated laminar flow air. The coater should also be in a laminar flow air
hood to prevent dust in the emulsion.
Expose the film through the base, and develop in the following developer:
Matrix Tanning Developer
Solution A:
Benzoatriazole 4.0 g
Oxalic Acid 40 g
Metol (Elon) 140 g
Pyrogallic Acid 120 g
Water to make 20 L
Solution B:
1 Level 2 gallon Bucket Sodium Carbonate added to water to make 40 L
solution.
Add 1 part A to 2 Parts B for normal contrast.
Process:
1) Pre soak the film in water 30 sec.
2) Develop for 2 minutes at 68 deg. f.
3) rinse in water for 30 sec.
4) Fix in non-hardening fixer 2 minutes.
5) wash in cold water 1 minute.
6) wash off excess (unhardened) gelatin using at least 5 changes of water
at 120 deg. f.
I use the following Dyes:
Acid Red # 289
Acid Blue # 25
Acid Yellow # 23
All three dyes transfer readily without skips or mottling. No mordant is
required, and the dyes are very wet-fast. I have used fixed out Ilford
Galerie paper, and have transferred to Arches paper with a thin gelatine
coating applied, and a silicone sealant to prevent bleeding. I don't
currently have final mixing instructions for the dyes, I'm going to
balance the dyes after I have perfected the film coating.
I am planning on selling this type of coater to anyone interested. I got
into this because I felt that I couldn't become
dependent on any one company (like Kodak) again for the most important
materials in my printing process. Since I would like Dye printing to
survive, I am making this info freely available, so please feel free to
post this info if you like. I may also try to coat pigments using the
matrix film emulsion. This would allow me to use my enlarger to expose the
pigment film.
Please let me know if you are interested in Dye Transfer, and in
particular if you are interested in coating your own film from either DT,
or Pigment prints. Thanks -
Jim Browning
james.browning@valley.net
http://www.well.com/user/justme/
603-448-6241