Humidification and/or Tween for Pt/Pd Printing.

[....Jeff....]

Hello Everyone,

As I am trying to work through some issues with plating/bronzing in the margins of my pure palladium prints, one common theme I keep coming across is the importance of sufficient absorption of the sensitizer into the paper. Printers seem to tackle this issue in two different ways (or some combination there of), Tween in the sensitizer and humidification. What I gather from the research I've done so far is that both methods are supposed to have essentially the same end result, increased penetration of the sensitizer into the fibers of the paper. With humidification, the increased moisture content of the paper is said to facilitate the coating being wicked deeper into the paper fibers than it otherwise would be at a lower relative humidity. Tween, being a surfactant, reduces the surface tension of the sensitizer allowing it to penetrate more readily into the the paper fibers.

My question, is it necessary to use both Tween and humidification to help mitigate issues such as solarization and to punch up Dmax, or is strict control over humidification alone sufficient? Specifically, I am considering doing some testing where I will be humidifying paper to 70-75% prior to coating and prior to exposure and wondering if there is any added benefit to using Tween at this humidity. Or worse, if it will cause excessive absorption and the unnecessary need for increased sensitizer. I'd be interested in hearing feedback on your respective experiences when it comes to balancing these two variables and your opinions on their necessity or redundancy.

Thanks,
Jeff

 

[pschwart]

I am considering doing some testing

This is highly dependent on your workflow and the particular paper you are using, so you will need to test.

 

[payral]

I never used Tween for any of my prints. I did use some humidification for some paper in special condition. Depends of the paper you use, where it's stored, darkroom humidity etc…
Each paper behave it's own way and you have to use it according to that. No general rules.

 

[clay]

Like everyone else said, it is all highly dependent on your paper and local atmospheric conditions. Someone printing in the high Houston, Texas humidity (me!) will probably have a whole different workflow than someone printing in Taos, New Mexico. One often overlooked aspect is the humidity of the paper prior to coating. Printers I know that live in arid areas tell me that it is beneficial with some papers to pre-humidify the paper several hours before coating. Just try changing one variable at a time until you hit on your magic formula. Good luck!

 

[AllenR]

I'll chime in here to say that I've found that pre-humidification of the paper to be key to producing consistent, even coating, given my work flow. Since I live where it is very dry, I have a humidification cabinet that holds the humidity at a constant 60%. The paper spends at least an hour in the cabinet before coating, then goes back in the cabinet to dry and it stays there until it is exposed. I've never found the need to use tween, given my work flow.

It has been my experience that keeping all conditions as consistent as possible, session to session, is key to success. Otherwise it is hard to determine what is going on, or what the effect that a planned change in work flow conditions has on the finished print.

 

[....Jeff....]

As most of you have alluded to, I do realized that local atmospheric conditions can have a major effect on prints, which is why I am essentially trying to eliminate that variable by using a humidification chamber. I have until now been maintaining my workspace at about 70-80F and 55-65% RH based on information I have gleaned from books and via the internet. I recently inadvertently got the RH up to the low 70s and was surprised by the observable increased Dmax during that session (nothing else was modified). I live in central California a few hundred feet above sea level and heading into summer I doubt that I will be able to maintain such high RH in my workspace as a whole, so am hoping that isolated humidification is the answer.

As for my paper, I am using some of the recent (Spring '11) Platine and will be testing some of the new Revere Platinum paper. In a sheet included with the Revere, B&S does recommend "1 drop of 10% Tween20 for every 15-20 drops of coating emulsion." I have been working with 3-5% dilutions of Tween, as anything higher makes it increasingly difficult to get a nice coating with reasonable drop counts (24/24 for 8x10) for my particular circumstances. I realize that B&S is in NM and conditions there are much different than they are here, so I do take it with a grain of salt.

Anyway, I started this thread just to kind of hear what other printers have tried and encountered when it comes to working with Tween and humidity, particularly humidification and the absence of Tween. I appreciate the responses so far and encourage printers to chime in with more of their own specific experiences, successes or failures.

Thanks,
Jeff

 

[....Jeff....]

I should have also mentioned that on the B&S paper about Revere Platinum they say that "If no Tween20 is available, pre-coat with distilled or filtered water. Allow paper to air-dry until slightly damp, then coat with your emulsion." Which leads me to further ponder the need for Tween with sufficiently humid paper. Anyway, enough talk, I'm out to the lab to actually do some tests. Will probably start without the Tween and see how it goes from there.

 

[donbga]

I should have also mentioned that on the B&S paper about Revere Platinum they say that "If no Tween20 is available, pre-coat with distilled or filtered water. Allow paper to air-dry until slightly damp, then coat with your emulsion." Which leads me to further ponder the need for Tween with sufficiently humid paper. Anyway, enough talk, I'm out to the lab to actually do some tests. Will probably start without the Tween and see how it goes from there.

Have you considered using a humidifier?

Don Bryant

 

[Green Rhino]

humidify

I use a clothing steamer to humidify paper. Depending on workflow, I'll do 4-5 sheets at a time, wrap them in a sheet of plastic to help even it out a bit and then open it up to dry slightly. The steaming of each sheet takes less than a minute works really well.

 

[Joe Lipka]

When you live in the Southern climes of the USA, you have air conditioning which reduces the humidity to a livable level. Humidification is a good thing to do. I used to do it twice. Once before coating and once before printing. I had to do the second one, because when I cranked up the vacuum easel, it sucked the water right out of the paper. Here's how I did it.

Joe Lipka Photography

 

[AllenR]

Stan Klimek gave me a tip at a B&S Platypus gathering several years ago that helps prevent drying of the paper while in a vacuum easel. He places the paper/negative sandwich ON a piece of acetate or mylar. I saw an increase in Dmax the first time I used this method and have been using it ever since. Of course, ymmv.

 

[PVia]

Stan Klimek gave me a tip at a B&S Platypus gathering several years ago that helps prevent drying of the paper while in a vacuum easel. He places the paper/negative sandwich ON a piece of acetate or mylar. I saw an increase in Dmax the first time I used this method and have been using it ever since. Of course, ymmv.

Ditto...!

 

[AllenR]

BTW, I meant to say vacuum frame, like on a NuArc plate burner. This technique isn't going to work on an open vacuum easel.

 

[donbga]

Stan Klimek gave me a tip at a B&S Platypus gathering several years ago that helps prevent drying of the paper while in a vacuum easel. He places the paper/negative sandwich ON a piece of acetate or mylar. I saw an increase in Dmax the first time I used this method and have been using it ever since. Of course, ymmv.

Ditto what Alan said. I use a layer of 0.002 optically clear Mylar.

 

[PVia]

Works great on a plain vanilla contact frame, too.

 

[....Jeff....]

Thanks for all the responses and information. My first crack at using a humidification chamber didn't produce much of a difference from the results I was getting before, perhaps because I had already been humidifying my work area to an acceptable level. Regardless of the level of humidity, I did still tend to find a small amount of Tween of some benefit (with Platine). I think I will go forward trying to keep the RH in my work area in the 60-70% range and adjust Tween as needed for specific papers. It looks like as long as humidity is above a certain level, say 50%, the paper surface is going to be the determining factor for the amount of Tween required, if any. As many of you've said, it just depends.

Thanks Again,
Jeff

 

[....Jeff....]

PVia, good to know, as I happen to print with this flavor of frame and had kind of written off the idea of acetate backing as something that was only beneficial for the vacuum frames. I'll give it a go.

 

[PVia]

Well, I started off using a contact frame with 7-8 minute sun exposures (which can get very hot), and it made a big difference. I've since continued the practices with the NuArc 26-1Ks, where I leave a large acetate sheet on the vacuum bed permanently for all processes.

 

[sharperstill]

Stan Klimek gave me a tip at a B&S Platypus gathering several years ago that helps prevent drying of the paper while in a vacuum easel. He places the paper/negative sandwich ON a piece of acetate or mylar. I saw an increase in Dmax the first time I used this method and have been using it ever since. Of course, ymmv.

Allen, the mylar goes under the paper? away from the glass?

Jon

 

[donbga]

Allen, the mylar goes under the paper? away from the glass?

Jon

A piece of Mylar goes underneath the paper and if available, an optically clear piece of thin Mylar can be placed over the negative.

This can be done with a vacuum easel or a good quality contact printing frame.

 

[sharperstill]

Where does one go for Mylar? What types of shops?

 

[pschwart]

I put all my negs in polypropylene bags, then put some impermeable backing behind the paper. This can be almost anything -- mylar, acetate, polypropylene, Yupo, whatever you have on hand.