DEAR RICHARD ET ALIA,
If my befuddled memory serves me properly, when I was taking photo chem with
Dr. Ron Francis and Theory of Photo Process with Dr. T h James, they pointed
out that there were two reasons that most developer instructions said start
with water at approx 120 or 125 F:
1) Most of the chems were more soluble at the higher temp.
2) The higher temp drove off most of the oxygen. Of course, boiling did a
better job but I think they said that boiling was too impractical and time
consuming for most photographers and that the difference in remaining oxygen in
solution between water at 120 F and water at 212 F was something like 10 or
15%...hardly worth the effort.
Again, this is my memory from 43 years ago~!
CHEERS!
BOB
From: "`Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
To: "pure-silver@xxxxxxxxxxxxx" <pure-silver@xxxxxxxxxxxxx>
Sent: Sunday, June 19, 2016 3:27:40 PM
Subject: [pure-silver] Re: More DK-50 Question (Was 5x7 Film)
The reason for boiling is to drive off dissolved air. Probably not necessary.
Look at the color of the powders. If they more than very slightly tan toss
them. Fresh powders are either white or slightly gray. I've found old Dektol in
bags that looked like coffee grounds and smelled awful. The old metallized
paper bags were not sealed very well. The cans were vacuum packed and seem to
last forever. Supposedly, the current Kodak plastic bags are well sealed.
On 6/19/2016 11:43 AM, Tim Daneliuk wrote:
On 06/19/2016 01:37 PM, `Richard Knoppow wrote:
BQ_BEGIN
I think the older ones are the two can variety. The reason many developers
come in two parts is that Metol, which is the main developing agent in them,
does not dissolve in a solution of sodium sulfite so it must be dissolved
before the sulfite is added. Kodak came up with a method of encapsulating the
sulfite (I don't remember the details) which allows all the ingredients to be
mixed as a single powder. You will find the same thing with Dektol, where early
packages separated the poweders into two parts, later, when supplied in bags,
it came as a single poweder.
When mixing the formula from scratch its probably a good idea to boil the
water first to drive off dissolved air to reduce the amount of oxidation of the
metol.
On 6/19/2016 11:25 AM, Tim Daneliuk wrote:
BQ_BEGIN
On 06/13/2016 09:54 PM, `Richard Knoppow wrote:
BQ_BEGIN
FWIW:
Kodak Developer DK-50
I see some formulations of NOS DK-50 around that are a single can and some that
are in two part A and B packets.
Questions:
1) What's the difference?
2) Is the stuff likely to still be OK to use if in a sealed can or packet, even
if it is quite old?
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BQ_END
--
Richard Knoppow dickburk@xxxxxxxxxxxxx WB6KBL
BQ_END
Thanks Richard. Are the NOS cans (probably >15 years old) probably OK
to use? I've never boiled the water, but I do use distilled for everything.
I've seen nearly 1 stop of variation due to water changes throughout the year
in my area. Distilled lets me develop the same where everywhere.
BQ_END
--
Richard Knoppow dickburk@xxxxxxxxxxxxx WB6KBL
