Na2-Pt./Pd. - Unable to get dark blacks

[Philipp Grewenbach]

Hello, I just recently started in Pt./Pd. Printing, and I ordered the Platinachrome kit from the japanese Ilford. According to the data sheets, it is "normal" Na2-Pt./Pd. chemistry, with Ammoniumcitrate as developer.

First, I wanted to determine my basic exposure time, so I just coated a small piece of Hahnemühle Platinum rag with the chemistry, and after it dried, I placed it in the contact frame, half under an unexposed but processed negative, half "naked".
I then exposed it using 4 15-watt UV-tubes from about 5cm distance, and used a piece of black matte board to mask in steps of 1 minute, 2, 4, 8, 16. After processing and drying the paper, I can see the difference between the area under negative and not disappearing around 4 minutes, but even at 16 it is not black, only some sort of "middle-dark" grey. In fact, there is not much of a change between 4 and 8 minutes, and none visible between 8 and 16.

What could cause such a problem?

I already tested the pH of the developer, it is 5.0, which should be fine. And the UV-lamp is certainly fine, as I printed salted paper with it just a few days earlier (exp times ~15 min., but salt takes much longer than pt/pd, right?)

Could I be using too few coating chemistry? I took the drop count from the Bostick and Sullivan tutorial and scaled it down to 5x7 inches. For 5x7, I used 5 drops each of Pd and FeOx, and 2 drops of Pt.
Could this be too few? (I am using a hake brush, but in the video they used brush coating as well...)

What else could lead to failure in obtaining real blacks?

 

[TheFlyingCamera]

There are LOTS of potential causes to this - it could be that 16 minutes is not enough. One reason for this could be low humidity - you want your ambient humidity to be at least 45-50%, and make sure the paper is properly humidified when printing. If your paper is too dry, you will have low contrast and long exposure times to obtain maximum black. I would try increasing your total drop count to 7:7:2, from 5:5:2. Depending on the strength of NA2, this can also have a restraining effect on exposure times, although it doesn't usually affect maximum black, just how long it takes to get full highlight details. Another possible issue is if the paper is too dry and it is absorbing too much chemistry, if you're having a hard time coating the image area, try getting some Tween20 to spread on the image area to act as a surfactant.

 

[Vaughn]

Hello, I just recently started in Pt./Pd. Printing, and I ordered the Platinachrome kit from the japanese Ilford. According to the data sheets, it is "normal" Na2-Pt./Pd. chemistry, with Ammoniumcitrate as developer...

Hello. just to be sure we are on the same page, you are using palladium salts and Na2...and no other platinum salts. Using all three together negates the contrast boost of the Na2, but it sounds like you are not doing that.

When I use Na2, I add a corresponding amount of the Ferric oxalate, so my ratio would look closer to 7:5:2 (instead of 5:5:2). It works (increased contrast/blacks), makes sense to me, FO is cheap -- anyone come across any issues with using the extra FO?

FC -- if the paper is absorbing too much solution, would not tween just make it worse? Whoops...was your last sentence addressing two different issues?

 

[Philipp Grewenbach]

Thanks Vaughn! Yes, I use Sodiumtetrachloropalladate, Ferric-Oxalate and Sodiumhexachloroplatinate, only those three. I will try the extra drops of FeO, that sounds good!
TheFlyingCamera, I will add a drop of Tween 20, thanks. Air humidity is 63%, so that should not be a problem...

 

[Philipp Grewenbach]

Ok, so I did a few more test strips and step tablets, and can now happily say that I do get nice deep blacks with a bit more drops, even more Ferric Oxalate (Thanks again Vaughn!) and one bit of Tween. For 5x7 I used 9 drops of Pd, 4 drops of Na2-pt, 15 drops of Ferric Oxalate, and one drop of Tween 20 10%. I exposed the paper 6 minutes after coating, and it worked really well now!
Thanks to you all!

...so I guess my droppers make smaller drops than usual

 

[Alan9940]

...so I guess my droppers make smaller drops than usual

Out of curiosity, are you using glass or plastic eyedroppers? I remember a comment years ago by someone at Bostick & Sullivan that the plastic eyedroppers are actually more consistent than glass.

 

[TheFlyingCamera]

Hello. just to be sure we are on the same page, you are using palladium salts and Na2...and no other platinum salts. Using all three together negates the contrast boost of the Na2, but it sounds like you are not doing that.

When I use Na2, I add a corresponding amount of the Ferric oxalate, so my ratio would look closer to 7:5:2 (instead of 5:5:2). It works (increased contrast/blacks), makes sense to me, FO is cheap -- anyone come across any issues with using the extra FO?

FC -- if the paper is absorbing too much solution, would not tween just make it worse? Whoops...was your last sentence addressing two different issues?

No - the tween will act as a surfactant, helping the chemistry to stay on the surface a little better rather than being sucked into the paper.

 

[fgorga]

No - the tween will act as a surfactant, helping the chemistry to stay on the surface a little better rather than being sucked into the paper.

This is NOT true.

Surfactants in general and Tween 20 specifically are used in alt process because they lower the surface tension of aqueous solutions. The lower surface tension allows the solution to penetrate into small spaces, such as the gaps between cellulose fibers in paper, more readily than a solution without surfactant.

Thus, Tween 20 is used when coating papers where sensitizer tends to bead up on the surface because it does not wet (penetrate) the surface of the paper well.

How a paper is sized is the major determinant in how far a solution will penetrate into a particular paper.

 

[Philipp Grewenbach]

Out of curiosity, are you using glass or plastic eyedroppers? I remember a comment years ago by someone at Bostick & Sullivan that the plastic eyedroppers are actually more consistent than glass.

I am using plastic droppers, just these standard ones that come in packs of 100, and I tend to replace them rather often. And of course each dropper only for one chemical

 

[nmp]

I am using plastic droppers, just these standard ones that come in packs of 100, and I tend to replace them rather often. And of course each dropper only for one chemical

I have observed that actual amount per drop (in gm) can vary quite a bit (as much as 30%) depending on the temperature and even the angle at which the dropper is held. I personally am very prone to forget the darn count mid-way. So I have resorted to weighing the solutions - it takes longer but I feel more certain. May be an overkill...

:Niranjan.

 

[doughowk]

I find eye droppers to be very inaccurate and inconsistent; so have switched to using pipettes.

 

[Vaughn]

No - the tween will act as a surfactant, helping the chemistry to stay on the surface a little better rather than being sucked into the paper.

I use Tween for the opposite reason...it allows the solution to quickly and evenly enter into the paper rather than sit on the surface.

The definition of a surfactant is something that reduces the surface tension of a liquid -- in the def. above, above you have defined the 'sizing' of the paper (internal and/or extrenal sizing).

 

[nmp]

I find eye droppers to be very inaccurate and inconsistent; so have switched to using pipettes.

Do you use one of those micro-pipettes that you can dial in the volume. I am thinking of getting one. They are a little pricey so I have to justify the cost.

:Niranjan.

 

[TheFlyingCamera]

I use Tween for the opposite reason...it allows the solution to quickly and evenly enter into the paper rather than sit on the surface.

The definition of a surfactant is something that reduces the surface tension of a liquid -- in the def. above, above you have defined the 'sizing' of the paper (internal and/or extrenal sizing).

Then that was my misunderstanding of how it worked.

 

[Vaughn]

Pre-Tween20 and when I first started printing, I use to blow-dry my freshly coated pt/pd prints, 1) Too quickly after coating and 2) too dry. All that expensive metal did not have time to soak into the paper. Nice printing-out image out of the exposure unit, but once into the developer a lot of that platinum and palladium just floated off the surface of the paper and into the tray.

 

[hirudin]

I purchased three micropipettes, 20ul-200ul, 100ul-1ml and 1ml-5ml, and I've never regretted the investment. It enables me to dispense 20 microliters right through to 5ml solution; I can accurately measure out 23 microliters of 20% platinum for Na2 palladium, or up to 5ml of solution for 20x24 images. They're fantastic!