Tetra-sodium EDTA is a really lousy clearing agent by itself because the pH is basic, which just locks the unused ferric into the paper fibers. Use it in conjunction with HCA, or mix your own with 1 Tbsp EDTA, 1 Tbsp Sodium sulfite, and 1/2 tsp Sodium metabisulfite (to make the solution slightly acidic and act as a buffer) per liter of water. Or just use Permawash or HCA by itself.
Dana -
Pt/Pd prints are beautiful, but it does take time and practice to learn how to get the results you are looking for. And because there are so few practitioners of this craft, the only way to learn is by word-of-mouth and/or trial-and-error.
kerik said:EDTA (tetra) by itself DOES NOT WORK. And I can't understand why B&S keeps telling people to use it as a clearing bath...
All of the Pt/Pd kits at Bostick & Sullivan that come with Tetra-Sodium EDTA also come with Ammonium Citrate as the developer because of a discovery my father made in the early 1980's. He realized that by allowing the prints to sit in the developer for 3-4 minutes, a simple bath of inexpensive Tetra-Sodium EDTA will clear the yellow stain from the paper.
The secret, he figured, was in the Ammonium Citrate Developer: It will combine with the Ferric Oxalate in the coating solution, and convert a good portion of it into Ferric Ammonium Citrate and Ammonium Oxalate. This has its benefits and caveats, though.
Anyone who's ever made their own Cyanotype solutions from scratch knows that Ferric Ammonium Citrate is extremely soluble. In fact, most people can clear the FAC from cyanotypes without any clearing agent at all.
On the other hand, anyone who's done a lot of Platinum/Palladium printing will tell you that Ammonium Citrate developer tends to change the color of your prints from a cool, neutral black when it's fresh, to a warmer tone as it ages. This is due to the ever-increasing Ammonium Oxalate content, which produces a similar warm tone to Potassium Oxalate.
So to sum it up: Tetra-Sodium EDTA works as a clearing agent if you follow the directions as provided by B&S.
If you use Potassium Oxalate or other developers, we recommend a 50/50 mixture of Sodium Sulfite and EDTA. If the stain is extremely stubborn, a 50/50 mix of EDTA and Potassium Metabisulfite will almost certainly work.
Thanks for listening to my rant,
Dana Sullivan
That said, I was also taught that it it was a good idea to pass the print through a plain water rinse immediately after the developer. That rinse removes most of the developer, and it also starts the clearing process. That's also a practice that I use regularly, and I've noted that much of the yellow ferric oxalate stain washes out in the water bath.
If
Exactly the problem I have here in the Detroit area. A water bath after development is the kiss of death for any print I make. I've been using Clay's method for a couple years now and haven't looked back. Like Clay, I pretty much use PO exclusively and think that many that take the process further do as well. I've always seen the B&S kits as a rock bottom place to start and they are great for that. There is so much more to the process though and many move away from ammonium citrate as a developer much like they do B&S's FO #2 as a contrasting agent. As Kerik and Clay have both stated, this (in my experience) renders standard EDTA fairly useless as a clearing agent.Mine is closer to 8, and a straight water rinse right after the developer is a guaranteed way to make the subsequent clearing a real pain in the butt.
No one has mentioned a quick and effective way to test for complete clearing:
Take a sample print through your entire coating, printing and clearing process. Put a drop of 1% potassium ferricyanide on a clear paper area (a masked edge helps here) that has been coated, developed and cleared. If you see any residual color (blue or tan) after you rinse off the potassium ferricyanide, you are not getting complete clearing.
Exactly the problem I have here in the Detroit area. A water bath after development is the kiss of death for any print I make. I've been using Clay's method for a couple years now and haven't looked back.
Bill
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