Re: Potentially stupid pt/pd question
Marek, That's the impression I've been getting, and it's on my list of things to try. Someone suggested having an abundance of oxalic acid crystals at the bottom of my developer jug (sorry, I don't remember who it was). That's also on my list. I think my current developer is just too far gone at this point; I may just start over with some fresh chemistry. We'll see how the filtering/replenishing goes. Normally I would just move on to another paper, but this stuff has a really nice texture to it that I'd love to be able to print on. And I already bought a box of it. And I'm stubborn. :) Camden Hardy camden[at]hardyphotography[dot]net http://www.hardyphotography.net On Tue, October 17, 2006 8:52 am, Marek Matusz wrote: > > Camden, > People usually think that replenishing is to add just fresh POTA solution. > That is only one part of it. As Clay and others noted the developer should > be acidic. Depending on the papers that you use the oxalic acid from the > developer will be used faster or slower. Papers with carbonate buffer are > notorious for depleting oxalic acid and changing pH of the developer very > fast. If your papers are of that kind you might need to add acid more > often. > ANd then some papers are just very difficult to clear and are more prone > to stain all together. In practice it might be easier to change the paper > then to mess with a chemistry a lot (not that it is not a good learning > experience). > Here is my work flow/clearing > I develop in POTA, room temperature (always 80F in Houston) for about 3 to > 5 minutes, perhaps longer then normal, but I found it helps with clearing. > Then I soak in a small amount of fresh tap water (say 0.5 liter to a liter > in a tray for 8x10 print) for another 5 to 10 minutes. I do not like > running a lot of fresh water through the print coming out of the developer > as it inhibits clearing in my practice. After that the print goes into a > clearing bath that hase some sodium ETDA (heaping teaspoon) and citric > acid (same amount) per liter. Ten to 20 prints culd be cleared in this > bath. I mix that fresh for each printing session. > Marek > Marek > From: Camden Hardy > Reply-To: alt-photo-process-l@usask.ca > To: alt-photo-process-l@usask.ca > Subject: Re: Potentially stupid pt/pd question > Date: Mon, 16 Oct 2006 16:42:55 -0600 (MDT) >>Clay, >> >>Thanks for clearing that up (no pun intended); that makes a lot of sense. >> >>I'm not sure about the pH of the water here, although I've never had >>problems clearing before. >> >>I think saturated developer is a more likely scenario. It's not that >> old, >>but I admit I have let it go longer than normal without replenishing it. >>I've got a shipment of potassium oxalate on the way, so I'll add to what >>I've been using and see if that helps. >> >>Camden Hardy >> >>camden[at]hardyphotography[dot]net >>http://www.hardyphotography.net >> >> >> > Potassium oxalate developer by itself won't stain paper. What is >> > probably going on is that your developer is absolutely saturated with >> > ferric oxalate from that it is removing from the print. So when you >> > put the print into the tray of developer, it is bathing in a >> > concentrated sea of ferric oxalate in solution. I would be willing to >> > bet that 1) your developer is old and saturated with ferric oxalate >> > and has a pH at or above 7.0, and 2) your rinse water is slightly >> > basic as well. This would explain the staining on both sides of your >> > paper. So it most likely IS a clearing issue, IMO, that you are >> > seeing, only you are doubling down by soaking your paper in a >> > developer loaded up in ferric oxalate removed from all your previous >> > prints. >> > >> >> Clay, I definitely tell you it's not the ferric that's staining, >> >> although >> >> it is the same color (which is why I initially thought it was a >> >> clearing >> >> issue). >> >> >> >> The entire sheet of paper is stained (front and back), not just >> >> where it >> >> was coated. The "paper white" >> >> >> >> It looks almost as if it spent some time soaking in a tray of coffee. >> >> >> >> >> >> Camden Hardy >> >> >> >> camden[at]hardyphotography[dot]net >> >> http://www.hardyphotography.net >> >> >> > >> > >> >> >
|