Test Strips with Platinum/Palladium

Discussion in 'Alternative Processes' started by Paul, Aug 12, 2010.

  1. Paul

    Paul Member

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    Just curious how many alt printers use test strips to determine ideal exposure with developing-out platinum/palladium printing, vs. how many inspect the faint latent image for clues, vs. how many wing the first print and take it from there.

    -Paul
     
  2. Vaughn

    Vaughn Subscriber

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    I wing the first print based on experience.

    If I don't hit it on the first, then I can usually hit it on the second. Sometimes I hit it on the first and get a great print -- I never get a test strip worth framing.
     
  3. Ian Leake

    Ian Leake Subscriber

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    The early platinum printers used to inspect the undeveloped image because they exposed under sunlight which is inherently variable.

    There's no need to do this nowadays. It's much more effective to use an artificial light source. Then you can make your first print with a standard exposure time and contrast. If your negatives are fairly consistent then you should be able to nail it quite quickly, as Vaughn said.

    In my opinion test strips are pointless, but using a step wedge can help you to learn how your contrast agent changes things (not essential though, because with a bit of practice your eyes will tell you everything you need to know).
     
  4. doughowk

    doughowk Subscriber

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    I use a densitometer to determine D-Max of neg (highlights with detail). Then compare it to other negs I've printed (keep notes). Combined with a split-back for checking the image during exposure, I can usually get close on 1st print.
     
  5. Paul

    Paul Member

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    Thanks for the input. I too have been avoiding test strips in favor of starting with an educated guess based on past prints and working from there. I am getting better at it, but have a way to go yet. Glad to have my working methods validated by the experiences of three accomplished printers.
     
  6. cowanw

    cowanw Member

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    Just to stir the pot. I am starting as doughawk is but I only have 6 data points so far and ny Ideal negative is still all over the place. So I find test strips to be great to get me in the ballpark both with contrast and time. I have only done portraits and put a 4x5 over the face. 4 test strips to a palladium mix per 8x10 sheet.
    Regrds
    Bill
     
  7. Ian Leake

    Ian Leake Subscriber

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    Using a standard printing time will help you here. The STP is the minimum exposure required to achieve maximum black through a developed unexposed negative (i.e. film base + fog).

    If your exposure is too long (and you're using a lot of palladium) then you will get solarisation; if it's too short then you'll lose shadow detail.

    Once you've worked out your STP (test strips or a step wedge make this easy) then you can immediately see if your negative is underexposed (lacks shadow detail), underdeveloped (highlights too dark), or overdeveloped (highlights too bright). You can then tune your process by adjusting your exposure and development until they are just as you want them.

    If your development really is "all over the place" then start with the Massive Dev Chart's N+1 time and work upwards.
     
  8. dpurdy

    dpurdy Member

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    I compare a new neg to an older printed neg by looking on a light box then I make a small print from an important area of the neg. I generally make a 4x5 test print for an 8x10 neg. I like to do it because it is fun to make small cropped images nicely brushed on the paper and use them for cards or little gifts. People love them. It can be a bit problematic with undoable divisions of the formula but usually there is a way.
     
  9. cowanw

    cowanw Member

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    I have found the step wedge to be a great help in choosing contrast grades.
    It is also helpful in figuring how many stops more I need to expose the Print.
    My all over the place negatives are really a trouble converting the book knowledge of large format and 4x5 experience to 8x10 cameras. Film developer and exposure testing as per the View Camera article didn't quite translate onto my studio portrait prints. More light and stronger development in an experimental empirical approach is getting me there. Also soft lenses need ?less exposure and more development for a given fstop than a sharp lens
    8x10 has its own learning curve, but its a lot of fun and I really enjoy plat/palladium.

    It did take the test strips, with the step wedge and part of the face in it, to help my really understand the theory. I just don't think they are "pointless" to the, new to the process, printer. "Tuning your process" and "working upward" might be where the quarter size test strips come in.

    It took my six different negatives of all different natures to really get me to the point I could say I understood Chapter 3 of Arentz. However I think, it is good for me to take a thin soft negative or a hard contrasty negative and force myself to understand what is to be done.
    and yes I have arrived in the direction of the N+1 development time empirically.
    and yes my std is about 200 units but just 2 stops extra is a whooping 800 units.
    and thanks for taking the time to reply in such a helpful way.
     
  10. Ian Leake

    Ian Leake Subscriber

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    That's fair, and "pointless" was the wrong word to use - especially as I sometimes use them myself in specific circumstances.

    The wonderful thing is that there are lots of different ways to make a print. What's important is to know which tools are available to you, and when to use them.

    While some tools may cost more (or less) in terms of time and materials, that's only one factor in your choice of tool. What works for you, what you're comfortable with, and what works best within the constraints of your space and equipment are also important.

    Enjoy printing :smile:
     
  11. sly

    sly Subscriber

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    Some great info here. Thanks!
     
  12. nick mulder

    nick mulder Subscriber

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    Step wedges are this thing that you get, play with for a little whiles - then forget ...

    (but worth every cent and every second)
     
  13. timgray@rogers.com

    timgray@rogers.com Member

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    I don't use test strips either, the main variable I find is relative humidity - where I live this can vary from 40% in winter to 75% in summer, and exposure times vary from 6 to 10 minutes.
     
  14. Loris Medici

    Loris Medici Member

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    Actually, I think absolute water content of air (and paper) is more important:
    Water content of air at 20C (68F) / 40% RH = ~15g (which is saturation humidity per kg of air at 20C) x 40 / 100 = 6g (per kg of air)
    Water content of air at 30C (86F) / 75% RH = ~28g (same as above, but for 30C) x 75 / 100 = 21g (per kg of air)

    As you can see, the water content of air changed more than 3x while the RH change was less than 2x! (1.875x, to be exact...)

    Another example:
    Water content of air at 20C (68F) / 50% RH = ~15g (which is saturation humidity per kg of air at 20C) x 50 / 100 = 7.5g (per kg of air)
    Water content of air at 25C (77F) / 40% RH = ~24g (same as above, but for 25C) x 40 / 100 = 9.6g (per kg of air)

    Now, things get interesting here; even if 40% RH (at 25C) is numerically smaller than 50% RH (at 20C), the absolute moisture content of air is more in that case, therefore your emulsion will be slightly faster!!! (Even if the RH figure was lower...)

    Moral of the story: Don't be fooled by just taking RH into account; you have to pair that with temperature, in order to be able to make a good educated guess...

    Regards,
    Loris.
     
  15. Ben Altman

    Ben Altman Member

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    Interesting analysis, Loris.

    So how many grams of water per square meter does properly humidified paper contain - as an order of magnitude? In other words could this be measured and controlled by weighing a sample of coated paper?

    Ben
     
  16. Loris Medici

    Loris Medici Member

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    Ben, I don't know; IIRC, there was such an analysis/test in Mike Ware's Cyanotype book, but I don't have it with me right now...

    I do know that carbon printers analyze the water content of their sensitized and dried carbon tissue by weighting it before and after sensitization; therefore, I assume the method you've described give some useful information indeed...

    Regards,
    Loris.
     
  17. donbga

    donbga Member

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    Test strips can be very effective and save material. Just take care keeping the paper strips at the same humidity level. So yeah I disagree that test strips aren't useful.
     
  18. Ian Leake

    Ian Leake Subscriber

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    The easiest way to control the water content of your paper/coating is to force dry it for a constant time (e.g. with a hairdryer) and then put it in a humidifying tank for a consistent time. The times depend on your paper but are easy to establish by trial.
     
  19. Loris Medici

    Loris Medici Member

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    I use a factorial drying time; I time how much a single drop of water (from a plastic pipette, on a piece of glass) takes to dry, and use (say...) 2x of this to dry my paper. 2x is just "a" ratio here, you can freely play with it (1x - 3x - ...), depending on the needs of your current process and the outcome... Works sufficiently fine for me.

    Bone drying then using a humidification chamber definitely works well -> but I don't have space for one myself...

    Regards,
    Loris.
     
  20. scootermm

    scootermm Subscriber

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    I just wanna add a bit of info from my personal experience printing in Pt/Pd.
    I've been making 12x20 pt/pd prints for about 3+yrs now and 7x17 and 8x10s for a few years prior to that.
    And I almost always do test strips. Especially with 12x20. Often I would skip it with 8x10s as the guesstimate method works fine.
    But when it comes to making 12x20 pt/pds and using +/- 1.2 ml of Ferric Ox, +/- 1.2ml of Pd, and a fair amount of drops of Na2 Pt.... the guesstimating method just isn't real practical and feasible.
    I usually have a stack of 4-5 12x20 negs I am printing and will estimate the contrast range Na2 drop count and coat a single sheet of paper with 1.2ml FO, 1.2ml Pd, and an estimated amount of Na2. After that sheet is dried and properly humidified I cut it up and do test strips for all 5 negatives. It's a process that works well with the method of shooting I do.
    Keep in mind that I am NOT working with predictable and measurably precise negatives. I shoot architecture, landscapes, random stuff outside, etc... with Efke PL100 in 12x20 and develop by inspection in PyroHD. So my negs are precisely identical... to say the very least.

    Just and FYI for some variation on working methods.
     
  21. timgray@rogers.com

    timgray@rogers.com Member

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    Fair enough, but the temperature is inside and doesn't vary - always at 72% within a degree or 2 and the RH is also measured indoors.
     
  22. Ian Leake

    Ian Leake Subscriber

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    What's important is the moisture content of the coated paper when it is being exposed to UV. Room temperature and humidity only effect the rate at which the coated paper dries in still air. They are therefore almost irrelevant to the look of your print if you force dry the paper (e.g. with a hair dryer or fan), control paper humidity with a humidity chamber, or have very long exposures (which cause the paper to dry out under the heat of the lights/sun). If they are fairly consistent then you can ignore them.


    Afterthought:

    If you air dry your paper in still air then room temperature/humidity will effect your drying time so being aware of them is a good thing. Likewise if you move your darkroom to a new location your timings may need to change due to the new ambient conditions. And extremes of temperature and humidity are unpleasant to work in. But it's important to understand that your objective needs to be to control the moisture content of your coated paper NOT to control room humidity.
     
    Last edited by a moderator: Sep 11, 2010
  23. Loris Medici

    Loris Medici Member

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    Ian, indeed what's important is the moisture content of the paper. And as stated in the afterthought, if you dry your paper in still air, the environmental conditions affect the vapor pressure of water, therefore the remaining moisture levels in paper, at time of the exposure. I don't use a hairdryer - except for cyanotype, where I leave the sensitizer soak in for at least 10 minutes and then force dry... - with any of the processes I do, because I found I get better prints (= better dmax / punch and hue) and more consistent results when I do otherwise. I also protect the paper by placing 2 mil thick impermeable sheets of mylar below and above it, therefore I don't loose moisture during exposure. (If you loose moisture during exposure, with pop pd, you'll get warm corners / edges vs. cooler center - which is awful 99% of the cases...)

    Regards,
    Loris.
     
  24. Loris Medici

    Loris Medici Member

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    Fair enough, if your temperature is always within +- 2F of 72F, then only taking into account the RH is perfectly OK. (As you have already experienced...) In my case, the indoors temperature of my studio will vary between 18-31C (64-89F) depending on the season, and the RH will vary between 30%-75% - independent of the season. Therefore, I have to be a little more fastidious...

    Regards,
    Loris.