Portioning Pt/Pd Chemistry

Neil Poulsen · Dec 10, 2005

Once one has the liquid forms of the Pt/Pd chemistry, what's a good way to portion it into the quantities needed for coating and printing? At the workshop I attended, we used drops. I don't think "drops" lends itself well either to consistency or to decent discrimination. For example, there's a huge difference between two and three drops of Pt.

I suppose one way would be to decrease the Pt concentation and use more drops. But, it seems to me that drops themselves are a problem. What if one loses their eye-dropper? Years of testing and experience goes out the window. There must be a better way that's reasonably priced.

Ian Leake · Dec 10, 2005

If you're worried about accuracy, then you could always try one of the calibrated droppers that chemists use.

matt miller · Dec 10, 2005

I use droppers. I've heard the term "pipettes" for measuring small quantities. I don't know what it is or where you can find one, but it might be worth checking out. I've been wondering myself if the dropper method is accurate, especially for small prints. So far it's worked for me.

clay · Dec 10, 2005

Pipettes, for example:
http://www.cynmar.com/product_info.php?products_id=7802
And pumps
http://www.cynmar.com/product_info.php?cPath=197_135&products_id=2060

indispensable for making accurate measurements, IMHO.

wm blunt · Dec 10, 2005

Neil Poulsen said:
Once one has the liquid forms of the Pt/Pd chemistry, what's a good way to portion it into the quantities needed for coating and printing? At the workshop I attended, we used drops. I don't think "drops" lends itself well either to consistency or to decent discrimination. For example, there's a huge difference between two and three drops of Pt.

I suppose one way would be to decrease the Pt concentation and use more drops. But, it seems to me that drops themselves are a problem. What if one loses their eye-dropper? Years of testing and experience goes out the window. There must be a better way that's reasonably priced.

I use eye droppers for printing 4x5, 4x10 and 5x7 and have no problem with consistency. As far as losing your eyedropper I almost never use the same one from session to session. All my solutions are stored with the regular caps and the droppers are rinsed with distilled water and laid on a paper towel on a shelf to dry. Next session I grab how ever many I need. Ever so often I purchase a few new ones when the rubber bulb gets a bit squishy(sp). If I was printing large negatives I would want pipets to keep from all that counting! I use the plastic droppers from B&S and they work fine.

photomc · Dec 10, 2005

clay said:
Pipettes, for example:
http://www.cynmar.com/product_info.php?products_id=7802
And pumps
http://www.cynmar.com/product_info.php?cPath=197_135&products_id=2060

indispensable for making accurate measurements, IMHO.

Thanks for the link Clay, have been looking for something like that. Broke my 25ml grad. that had been with me for 30+ years. No longer work in a lab and was not sure where I could get a replacement.

Anyone ever use the small beakers in place of a shot glass to pour from? Wondered if it made any difference.

John Bartley · Dec 10, 2005

A couple of questions from someone who has not yet done any alt processes:

1) From what I've read, the ratio of chem's is drops / drops. How does the viscosity of the different chems affect the size of the drops and thus affect the ratio of chem volume? Is the ratio "that" critical? I guess a person could measure the drops into a small grad to find out and then use a pipette from then on?

2) I've always thought of pipette suction as coming from the lungs - sounds kind of risky, but I see a pipette pump listed in one of the links above. How do you folks who use pipettes do this?

cheers

Photo Engineer · Dec 10, 2005

For a given liquid, a drop is a drop. And so, if you have some Pt or Pd solution at a given constant concentration, you may find that 20 drops = 1 ml or some such. This will always hold true for that dropper and that solution due to viscosity, density, gravity, the hole size in the dropper and etc. You cannot change the physical laws governing formation of one drop.

But, change droppers or solution concentration and you have to recalibrate your drop size/quantity. You may find that 22 drops = 1 ml or some such.

Bottom line is that with one dropper and one solution the drop method is quite accurate for measuring tiny quantities with reasonable assurance that you can repeat yourself.

PE

Joe Lipka · Dec 10, 2005

Eye droppers and brown bottles from the local pharmacy (chemist) have worked just fine for me. If you can't be accurate, be consistent. Since there is always so much variation in these hand coated processes, you will always find a way to get just what you need to make a successful print.

Kerik · Dec 10, 2005

Let's not be too anal here, folks. You will find that the droppers are more than consistent enough that you don't have to worry about it. The glass and plastic droppers are slightly different from each other, so don't mix and match plastic and glas. And the viscosity of the ferric and pt/pd solutions are close enough for jazz.

The pipette pumps are very easy to use. No inhaling involoved... well, at least no inhaling of the solutions.

As Clay once told me, you shouldn't try to measure a brick with a micrometer.

Kerik · Dec 10, 2005

Oh, and I wouldn't definitely NOT recommend diluting the solutions so you'll have more drops and therefore more consistency. You may dilute the stuff too much and get weak prints (although I'm sure they'll be consistent!)

nick mulder · Dec 10, 2005

The discrete nature (as opposed to continuous) of a drop is countered in my case by the fact that I am using many of them so the proportional error in trying to achieve non standard (tending towards irrational if you will) proportion is minimised to a level well under the other possible errors added to the system by every other determining factor - which in my case taking into account all i am yet to learn is still just the composition of the image itself :rolleyes:

clay · Dec 10, 2005

Hey!! you must write artist's statements for a living!

nick mulder said:
The discrete nature (as opposed to continuous) of a drop is countered in my case by the fact that I am using many of them so the proportional error in trying to achieve non standard (tending towards irrational if you will) proportion is minimised to a level well under the other possible errors added to the system by every other determining factor - which in my case taking into account all i am yet to learn is still just the composition of the image itself :rolleyes:

nick mulder · Dec 10, 2005

clay said:
Hey!! you must write artist's statements for a living!

yeh!

I was going for gold on that one... well spotted

I could have summed it up in two words:

'dont worry'

...but was feeling a bit lonely at the time, the rant kept me company (;

matt miller · Dec 10, 2005

I was thinking the same thing

Portioning Pt/Pd Chemistry

Privacy & Transparency

Privacy & Transparency