Re: Homemade Potassium Oxalate

Don, here is Eric Neilson's note to me of sometime back, along with my
method which was at least in part derived from Eric's and other methods.
Same goes for the Cold Bath developer. Can't be absolutely sure that I
updated the doc the last time out, but one thing I can tell you is that it
gets quite active for a while, so use extra large containers and make the
prep outside or in a very well ventilated room with a large sink.

n

Preparation of Potassium Oxalate

Eric Neilsen wrote:

I use 2 lbs of Potassium Carbonate (mono) and 1.75 lbs Oxalic Acid. First
dissolve the potassium carbonate in about 2 1/2 quarts ( 2500ml) of water.
I use distilled or similar quality water to help keep the product as clean
as possible. Then slowly add the oxalic acid with stirring. It will bubble
quite energetically, as it gives of CO2 and heat. You may consider doing
this outside, but a good lab should handle it just fine. When you have
added enough oxalic acid, the bubbling will stop. Top off to make 1 gal. I
usually add an extra 150 gm to the fresh batch to keep it on the acid side.

Nick Makris wrote:

To make Potassium Oxalate developer for PD/PD prepare as follows:

Might be better to do this outside or at least with good ventilation as the
process gives off CO2, some heat and a significant amount of bubbles.

To make 1
Gallon 2 Qt 1Qt

Start with distilled water (ml) 2200
1100 550

Add grams of Pot. Carbonate mono 907 454
227

with stirring until dissolved.

Measure Oxalic Acid (gm) 794
397 199

Slowly add small amounts of

the above measured Oxalic Acid with stirring,

waiting each time you add until bubbling

stops - continue until all of the above measured

amount has been added - produces balanced ph of 7.0.

Then add more Oxalic Acid to 60
30 15

keep solution on the acid side.

Remember, add slowly - produces 5.1 ph.

Top off with distilled water to make desired quantity.

On 11/2/01 I prepared a fresh batch of Cold Bath Developer; the old
developer had a PH of 5.9 and the new batch was 5.0. The discernable
difference was add contrast - ie, less density in the highlights and more
density in the shadows and it may have been slower to react???

C:\foto\documents\Potassium Oxalate Prep.doc

PT/PD Cold Bath Developer

Nick Makris wrote:

I have run across a formula for PT/PD Cold Bath Developer which is as
follows:

175 gm Pot Oxalate, 75 gm Pot mono Phosphate and 1 qt. H2O

Eric Neilsen wrote:

It has several different formulas but the essence is that about 180g
Potassium oxalate with 50 to 60 grams Potassium Phosphate mono basic. You
should be able to dilute the Pot. Ox. solution you have made just short of
1:1 with water and add the potassium phosphate mono basic. The Formulary
also sells the potassium phosphate mono basic. It may give you a bit more
contrast than the standard PotOx developer. You can dilute your standard
Pot Ox with water and it will give you a print that is slower, and with more
contrast but it will have more grain or at least that is what I saw with
those combination of processing elements.

The potassium oxalate developer that you have made is close to saturation
(as prepared above). This explains the need to dilute it in order to add
something else to the solution.

Therefore, to make a quart of Cold bath developer from prepared/saturated
Pot. Ox. solution: start with 20oz of the above and add 12oz (60%
dilution)of distilled water. Slowly add 50-60gm of Potassium Phosphate Mono
basic, continue to stir until completely disolved. If there is any
undisolved residue, add just a little distilled water, stir and allow to
stand and repeat if necessary. Adjust this instruction as required.

The use of this may be required in order to render the desired, appropriate,
or required color of the final images. This is the last step after
determining how much PT vs PD, and the temperature of the developer. The PT
will cool off the PD and the Pot Ox will warm up the PD.
Received on Fri Mar 4 10:05:04 2005