Calcium oxalate on palladium prints??
I have a problem with, what I believe is, calcium oxalate forming on my palladium prints. There is a good topic on this, but it appeared that CO wasn’t the culprit in the end and the discussion ended there.
The details: (I have always used ammonium citrate until now, and have had no problems with the workflow.) I develop the prints in PO (mixed with tap water) at room temp. I then move the print straight to a clearing bath of tri-sod EDTA and sodium sulphite (again mixed with tap water). A plain water bath has produced clearing issues in the past. Within a couple of minutes, minute, insoluble crystals/scum form all over the print, which rub of as a yellowish powder when dry.
A couple of observations:
- The first print is fine, the second, the crystals are visible only when the print is dry. The third print is covered. This suggests to me that as the clearing bath gets loaded (which is quickly since I use no water bath and PO does not clear as effectively as AC), the problems occur.
- The crystals only form on the area of the paper that has been coated. Borders are free.
- Double-coated prints are much worse.
Ideally, I should just ditch everything and start again with distilled water, but since PO is about 25 GBP per litre, I would like to avoid this. Does anyone know that if I mix the clearing bath with distilled water, will there be insufficient calcium from the PO to form the crystals? Or, that although the problem appears to form in the clearing bath, it does in fact happen in the PO but manifests itself in the clearing bath. The fact that the first print is OK suggests to me that, for some reason, the (increasing amount of) oxalate and calcium in the clearing bath is responsible. Any suggestions? I don't really want to ditch the equivilent of $100 of PO.
Also, perhaps a different thread, but perhaps related, I find the PO a little too warm. I have heard it possible to combine Po and ammonium citrate to produce a slightly cooler developer. Is this correct? And, as an aside, would the reduced oxalate in the dev, reduce the probability of creating CO on the print?
Or is it something completely other than CO???? My FO is getting on the old side, but I don't se how this would create these problems.
So many questions.
The cheapest, easiest way to go may be to mix up your own potassium oxalate developer from scratch using distilled water and potassium carbonate and oxalic acid. It is very easy to do and is very economical. You can also ensure that your developer pH is around 6, which will mitigate these strange problems you are having. I buy oxalic acid and potassium carbonate in 25 pound buckets and mix the developer myself for a significant cost savings.
Originally Posted by gwatson
Originally Posted by clay
Who do you use as your source?
I use the ChemistryStore.com and homemade PO works great and saves money.
Originally Posted by billschwab
Ditto Don's suggestion:
The rough economics using the largest bags (~50# each) will yield approximately 25 gallons of developer for $140 (not including shipping)
Compare this to $18 per pound for premade potassium oxalate which will yield about 2 liters of developer. (assuming you use 250g/liter)
The math is pretty compelling.
Originally Posted by billschwab
Sponsored Ad. (Subscribers to APUG have the option to remove this ad.)
Thanks Clay and Dan.
Yes, thanks guys. Remarkably, both chemicals are available in the UK, although not at your prices, but still significantly cheaper. I'll start again from scratch.
Thanks Don and Clay, that is very good information.
How much Oxalic Acid are you using per Qt or liter?
Mix what ever volume you need with these proportions:
Originally Posted by JLP
2 lbs Pot Carb and 1.75 lbs Ox Acid to make 1 gallon of solution. After completely disolving the Pot Carb (which will heat up the solution), slowly add the oxalic acid while stirring. There will be a lot of fuming and bubbling when you add the OA so use a large container to avoid splattering the adjacent environment. A 2 gallon paint bucket from the hardware store should work well as a mixing pail.
Once all of the OA is added and mixed dissolve a couple tea spoons more to make sure the mixture is acidic. If you have pH papers test for a pH > 6 and < 7.
I usually try to keep the PO clean by filtering every few prints for large prints or at the beggining of every printing session if doing small prints.
Last edited by donbga; 03-17-2007 at 07:56 PM. Click to view previous post history.
Thank you so much, great info and certainly a lot less expensive to keep fresh developer in the tray.
Hope to be coating my first sheet next week.