Gary Miller (gmphotos@earthlink.net)
Sat, 31 Jul 1999 23:31:42 -0700
I had some time today to do some testing with DOP on Platine to try and
locate the source of my bronzing/solarization effect. I had many wonderful
suggestions from list members, about a dozen different ones including
overexposure, not enough metal, not enough solution, paper needing to be
humidified, paper needed not to be humidified, resting time after coating,
method of drying, room drying verses forced drying, heat drying versus cool
drying, bad paper, too high a percentage of potassium chlorate, exposing
paper bone dry, exposing paper with some moisture in it, and others I am
probably forgetting, and I thank each of you for the ideas. I have listed
all the details below for the scientifically minded. For those not
interested in detail, you may skip to the conclusions at the bottom of this
post.
Material and Methods
Materials were from Bostick and Sullivan and consisted of:
Solution #1- ferric oxalte 6.5 gm in 25 ml distilled water
Solution #2- ferric oxalate 6.5 g, potassium chlorate 0.33 g, in 25 ml water
Palladium solution #3- palladium chloride 2.3 g, sodium chloride 2.0 g, in
25 ml water
Platinum solution #3- potassium chloroplatinite 5 g in 25 ml water
Tween 20- 10 % solution
Paper- was Arches Platine from Pearl Art Supply in San Francisco, CA. The
front surface, right reading of the watermark, was always used. Paper was
humidified in a cool mist humidifier for 5 seconds on the front, 5 seconds
on the back, and then 5 seconds on the front in the cases where noted. Some
cases the paper was not humidified prior to coating.
Coating- all coating was done with a 5 inch glass coating rod over a 4x5
image area. Coating took from 4 to 6 passes each time
Resting- after coating all examples were allowed to rest from 3 to 5 minutes
before forced drying
Drying- was with a hair dryer set on low heat setting held approximately 6
to 8 inches above the paper surface. The front was dried for about one
minute, then the back for 2-3 minutes, then the front again for 1-2 mins
until the paper was thoroughly dry, brittle, and showed some curling. Dryer
was in constant motion
Exposure- was on an 11x14 inch horizontal UV light box with black light
bulbs. Bulbs were approximately 2 inches from sensitized paper during
exposure
RH- was about 65%, room temperature was about 70F (ambient)
Development- was in potassium oxalate (25% in distilled water) at 85F for 90
secs.
Clearing- was three baths of Perma Wash hypo clearing agent, 25 ml of
solution to 1000 ml of water. Clearing in each bath was for 5 minutes.
Washing/drying- prints were washed in an archival washer for 30 mins then
dried on fiberglass screens.
Nomenclature; Drop schedules are noted in the following format
Sol'n 1- Sol'n 2- Pd- Pt- Tween
Test 1:
drop schedule : 5-1-3-2-1 (5 of Sol'n 1, 1 of Sol'n 2, 3 of Pd, 2 of Pt, 1
of Tween 20 (10%)
Total drops used : 12
Paper was humidified before coating
Dried completely before use
Exposure time was 6 mins
Result: Showed solarization in the deepest shadows
Exposure range : Step 4/5 to 17
Test 2:
drops : 5-1-4-2-1
Total : 13
Paper was humidified before coating
Dried completely before use
Exposure time: 6 mins
Result: Showed less solarization than Test #1
Exposure range : Step 4/5-17
Test 3:
drops 5-1-4-2-1
Total: 13
Paper was not humidified prior to coating
Dried completely before use
Exposure time : 6 1/2 mins
Result: Showed less solarization than Test #1, same as Test #2
Exposure range: Step 4-16
Test 4:
6-1-4-3-1
Total: 15
Paper was humidified before coating
Dried completely before use
Exposure time: 6 1/2 mins
Result: Showed same solarization patterns as Test 2 and 3
Exposure range: Step 5-17
Test 5:
5-1-3-2-0
Total = 11
Paper was not humidified before coating
Dried completely before use
Exposure time : 6 mins
Result: Showed no solarization anywhere in the print
Exposure range Step 3/4-16/17
Test 6:
5-1-3-2-0
Total = 11
Paper was humidified before coating
Dried completely before use
Exposure time : 6 mins
Result: Showed no solarization, but more contrasty than Test #5 and grainy
overall.
Exposure range : Step 3-15
CONCLUSIONS;
In my testing the following was seen;
1. The number of drops used for coating seemed to have no bearing on the
solarization/bronzing problem
2. Humidifying or not humidifying the paper prior coating seemed to have no
bearing on the solarization/bronzing effect
3. Use of Tween 20 (10%) seems to be the cause of the solarization/bronzing
effect in my system when used in the sensitizer coating on Platine. Tween
20 had no adverse effects when used in the solution coated onto Cranes
Platinotype
4. Pre-humidifying the paper prior to coating produced worse results for me
than not humidifying with increased contrast and graining seen. Since the
RH is around 65% it seems that no humidification is necessary for me when
using Arches Platine. Humidification prior to coating showed no adverse
effects when using Cranes Platinotype paper.
5. Average exposure time with the Platine was about 6 mins. In the same
formulation on Cranes Platinotype exposure time was 16 mins on average.
6. The method of drying after coating or the amount of rest time seemed to
have little effect, but further testing of these variables would be
necessary to make definite statements.
7. Overexposure did not produce solarization in a formula that did not
contain Tween 20 (10%) on Platine
I bet you could never tell that I used to be research scientist. Thanks
again to all those who gave advice.
Gary Miller
This archive was generated by hypermail 2.0b3 on Thu Oct 28 1999 - 21:40:39