Pt/pd Printing - Making a test strip

[Alan9940]

Though I've been printing pt/pd sporadically for several years, I've decided to get more serious about it. I'd like to make a test strip to determine a Standard Printing Time, but it seems that the 4-ply matboard I normally use for making test prints under the enlarger for silver printing is not heavy enough or not UV blocking enough to work. Rather than nice clean strips across the print for each exposure increment, I get more of an overall exposure with, maybe, faint strips.

I use an Edwards Engineered Product UV exposure unit where the printing frame is placed inside the box with a door that flips down to close it. Therefore, I can't make a test strip exactly the way I do it for silver printing. I'm thinking I need some kind of UV blocking material, perhaps a few different sizes, whereby I could place a piece on top of the frame, carefully slide the frame into the exposure unit, expose, rinse-n-repeat for, at least, a few exposures across the paper?

Anyway, how do you alt process printers using UV exposure handle test strips?

Thank you for any insight provided.

Alan

[cowanw]

A small Stouffer 21 Step inserted along side your negative will help you know exactly how many stops of time you need to alter to change a particular density to another.

[tgtaylor]

Alan - I haven't yet printed a Pt/Pd but have printed a few dozen Kallitypes which are very similar. I use the sun which is plentiful here in sunny California rather than an exposure unit and what I have found is that each negative is different. For example the last negative required 6 minutes is the open shade and 45 seconds direct sun and another 4 minutes is the shade and 25 seconds in the sun. So you have to know what it should look like when you pull it and to check. I usually start checking at the 4 minute mark.

Thomas

[peter schrager]

Although I'm not answering your question I strongly advise taking a class...tillmsn crane is a great instructor get in touch with him

[jim10219]

I just use black construction paper. You can also use a manila envelope. Lots of things will block UV light really well. You don't need to get fancy with it. I just cut them into strips of the appropriate width and place a few coins on the edges to keep them down, then expose for whatever desired time increment, pull the UV blocking sheet over a row, and repeat. I usually start off with a 15x15 negative that has 15 rows of 15 steps each. I just slide the UV blocker over 1 row at a time to get a rough idea of how it will look at different intervals. I usually have a pretty good idea ahead of time of how long it should take, but if I don't, I'll do it twice. Once for a rough figure, say pulling the sheet after every minute, and the second to fine tune it pulling the sheet over every 10 seconds or whatever is appropriate depending on how long the first test suggested. Then I have a 10x10 negative with 100 boxes that increase density by 1% each. I print that at the time I determined from the first test, and I get my curves. I just scan that final print into PS and measure each square with the eye dropper (after converting to B&W and adjusting levels for max and minimum possible tones) looking for an example that gives me the desired output density (say 25%), and it's location on the chart tells me what the input was needed on the negative to create that. So if the box that has 25% density is number 31, I'll set the curve's input to 25 and output to 31. Therefore I can get a really reliable procedure down for just about any process with just two exposures, saving time and money. Although, if you change anything in your setup, like the type of paper or coating procedure, you can expect to have to redo this whole process for optimum results.

[Alan9940]

@cowanw - When printing analog negatives, I do usually include a Stouffer Step strip just as a double check that tones are falling where I expect. With digital negs, I have a step strip that prints out right alongside the negative. However, neither of those will tell me what minimum exposure time is needed to produce dMax through the film. One simple test strip using blank film will tell me all I need to know.

@jim10219 - if you use something as simple as black construction paper, then I'd think my black 4-ply matboard should work. Perhaps I wasn't holding my mouth right or didn't have on my lucky underwear when I tried making a test strip the first time. I will try, again, using a technique very similar to what you describe. Thank you.

[bob carnie]

I use a thick black lexan material for step offs when making Pt Pd prints . Very opaque.

[cowanw]

Not to want you to change anything, but if you lay down a blank film, a stouffer negative and your paper, and exposing over time, won't the first step of unchanging black be your minimum exposure time (Calculated from actual time)? Or am I out to lunch?

[tgtaylor]

I use test strips in silver printing to put the general exposure in the ball park and make adjustments to it from there. There is no substitute for not knowing what to look for in the work print. The advantage of the alt print is that you can open up the printing frame and see where the exposure is at, that is, if you know what you are looking for. If after development the print is a little too dark/light, then you know where to go with the next one. But maybe you can find an app in the store that will tell you all that.

Thomas

[Vaughn]

The thick 4-ply might be throwing a shadow, thus no sharp line...especially separated from the paper by the glass of the contact print frame. I use strips of rubylith.