Determine the basic exposure for palladium printing

[duckie]

The attached test strip was the one that I made for determining the basic exposure for palladium printing. I used a blank sheet of Pictorico Ultra Premium OHP Transparency Film to cover part of the coated area on Bergger COT-320. And It turned out that the area covered by the film would never reach the same density as the uncovered part, even if I had increased the exposure time up to 6 minutes. Its density was in gradual increase in brown, could not even reach dark brown, while the uncoverd part seemed to have reached its Dmax within 2 minutes.

And for coating the paper, the suggestions I found on the net are telling that 6 drops of Ferric Oxalate plus 6 drops of Palladium solution would be sufficient for a 4X5 -inch image. I didn't realize that it was not sufficient until it turned out to be. What's the common practice in this situation? Let it dry down and give a second coating?

Sorry for the naive questions as I'm all new to the process.

Thanks much in advance for any kind reply!

 

[payral]

If you look at a 21 steps tablet like Stouffer, you will see that you are about 6 steps or 3 stops far from black, so your next exposure time should be 48 minutes and you will be much closer to the black.

 

[DennyS]

I would guess 16 drops might be closer to correct but it depends on how you're coating the paper (rod? brush? what kind? did you prewet the brush?) and of course which paper you are using. Common practice is to use the correct volume of solution to completely coat the area needed. A second coating to cover bare spots is not likely to produce a satisfactory result. What kind of light source are you using?

 

[duckie]

@payral: OK, I'll try 48 minutes and have a look. Thank you for the suggestion.

@Denny: Thank you for the comment. I'm using 8 black light tubes (30 watts each) and the distance between the tubes and the exposure plane is about 6 inches.

 

[Joe Lipka]

Remember to keep records on everything you do. Written records. Platinum printing is one giant science experiment. You don't know what you did unless you wrote it down beforehand. Your memory isn't good enough to remember everything unless you write it down.

 

[DennyS]

What Joe said is good advice, the more notes the better. I'm surprised by the exposure times, I'm using a bank of 12 25 W bulbs about 1.5 inches above the print and I use an exposure time of 3 minutes. So many variables though, maybe an experienced printer who is nearby could come over and take a look at what you're doing. Where are you?

 

[duckie]

Thank you for the advice, Joe. I'll keep records.

Denny: According to Dick Arentz's book I had thought it might only take few minutes at most. I'm in HK. It's ok. I'll cherish the challenging and rewarding experience

 

[duckie]

I kept testing for longer exposure time, while shortenning the distance between the tubes and the print.

Finally I shortened the distance to about 1.5 inches and exposed for 2.5 hours (see the attached, the right side covered by Pictorico Ultra Premium OHP Transparency Film). The result that it's still far from being dark is driving me crazy.

Can anyone give me some advice? I really don't know what to do next. Longer time would lead to solarization, as what the four-hour strip showed. And isn't it unreasonable to expose a print for several hours?

Thanks and sorry for my ugly brush strokes

PS: The paper is Bergger COT320, prewet for ten seconds before coating. a Hake brush. 6 drops FO+6 drops of palladium solution for an image area of 4X5 inches.

 

[clay]

Your times seem extremely long to me. Are you using a contact printing frame? And it is possible that it has UV blocking glass in it? My normal bright sunshine exposure times are about 5 minutes for straight palladium and my UV fluorescent box is about the same.

Something is amiss if you ask me.

And beware of too long exposure times with palladium. It actually exhibits reversal, whereby longer times result in lighter print density after it reaches a maximum.

 

[Doyle Thomas]

new to this thread, i'm using OPH for cyanotype and have noted the same thing, higher density in the area not covered by the transparency, increasing exposure time no help. maybe its just a diffusion contrast or light scatter issue. OPH's claim to fame is that it has the highest clay content (to receive and hold the pigment) of any transparency material around, that's why the milky color. Ink Press also holds pigment well and is more transparent.

 

[duckie]

Clay: No, I didn't use a contact printing frame, just two pieces of glasses. Five minutes...sounds like heaven to me.

There's one thing I can't understand. Should there be anything wrong with the paper, the solution, the tubes or the glasses, the part that was not covered by the Pictorico film shouldn't have reached its Dmax within 2 minutes in my first strip, and in totally dark too in the following strips with longer exposure time except for the four-hour one.

 

[clay]

Sorry I did not snap to the fact that you are using the Pictorico OHP Ultra Premium. The Ultra version has this exposure problem and I avoid it like the plague. I recommend using only the regular Premium OHP for any UV processes. The Ultra is Ultra-bad news for anything needing UV light.

 

[DennyS]

Clay, I've been using the the Pictorico Pro Ultra Premium OHP and I get a 3 minute exposure time with Pt/Pd or gum printing. I've ever had any problems with it.

 

[clay]

I can never get a solid black with the Ultra. If I do a side by side exposure with part of my palladium coated paper not covered by the Ultra, the Dmax of the Ultra covered piece never reaches the Dmax of the uncovered piece. This does not happen with the premium. I took great care to test this with a generously coated sheet of paper, and repeated the test several times, always with the same result. As always, YMMV. Perhaps some light sources cause different behavior. I tested it both in my BL fluorescent box and my Amergraph ULF28 and observed the same thing.

 

[DennyS]

Clay, I'm exposing under a bank of 12 closely spaced F25T8BL 18 inch tubes. I just took another look at two exposure tests I ran earlier this week on Bienfang marker paper and Fabriano Artistico Extra White with 75% Pd/ 25% Pt, each exposed 3 minutes, developed in room temp Potassium Oxalate and I can't see any differences in the Dmax at the edges of the Ultra. Curious.

 

[duckie]

Thanks Clay & Denny. I would try a different light source and see what will happen. Denny, may I ask where you bought the tubes? I'm searching for F30T8BL on the net and don't know what the difference would be for difference prices ( varying from $8 to $17 per tube). And also not sure if I should try instead Philips BLB tubes.

 

[DennyS]

Sudek, I bought my bulbs years ago from ebay. I remember seeing a large variation in pricing, and I don't know if the different prices have any impact on performance. I'm guessing that any bulb with the same spec should perform about the same. Also, I think you should probably avoid the BLB bulbs since they add an additional filter into the light path. Hopefully someone with more knowledge about bulbs can add some insight.

 

[duckie]

I just got back to the experiment.

Light: a bank of 8 30W HITACHI tubes about 4.5 inches above the print (the tubes are newly changed)
Paper: Bergger COT-320
a 21 steps tablet(I couldn't get the 31 steps tablet locally),half of which covered by Pictorico Ultra Premium OHP Transparency Film

I exposed for 20 minutes and 40 minutes respectively, but the steps are all far from black,yes,even the part not covered by OHP film. Then I changed the glass from 5mm to 2mm and exposed for 40 minutes.Same result.

Frankly speaking, it's making me feel despair. How come you can make it in just few minutes? I have no idea what I've done wrong. What should I do? To expose for two hours is not a good idea,right? I understand too long exposure is not right for making palladium prints.

 

[duckie]

The attached is the one exposed for 40 minutes with the 2mm glass