From: Nick Makris (nick@mcn.org)
Date: 09/29/03-06:48:41 AM Z
Mark, Congrats to your daughter.
I'm not using any wax or oil on the tests I'm running and I have run a pure light test (no substrate). Those results, which also indicate a problem, are inconclusive. My sense is that something is contaminated. I guess I'll start over with a new bottle of PD and some freshly mixed FO.
Thanks for your help,
Nick
----- Original Message -----
From: Ender100@aol.com
To: alt-photo-process-l@skyway.usask.ca
Sent: Saturday, September 27, 2003 10:09 PM
Subject: Re: PT/PD density/contrast/definition
Nick,
I would tend to agree with Sandy King's response, that you have probably overexposed your negative of the digital step tablet on the waxed paper and perhaps have too much contrast in your mix. One thing I wasn't sure of in your description, you said you added 1 drop of PT to the mix for color. What are you using for contrast? If the PT you added was the famous "magic bullet," sometimes called "Na2," or Sodium Chloroplatinate, then my guess is you have an extremely contrasty mix for your negative. See: Dick Arentz Na2 Contrast Ranges, ©Dick Arentz.
I'm trying to read between the lines though regarding what you have described—if I have errored in my interpretation, pardon any errors.
You can easily test your waxed paper substrate for the proper exposure value by using a trick that perhaps many people know, but was taught to me by Sam Wang. For now, forget the "digital step tablet" because it may not give you accurate information. In addition, if you measured the "highlight density" (2.2) of your digital step tablet with a standard transmissive densitometer, it might be incorrect due to the difference in how inks block UV light.
You need a 21 step tablet, like the Stouffer's # T2115 (about $5)—www.stouffer.net. If you don't have one of these or a similar one, then stop whatever you are doing and get one right away. They are indispensable.
Prepare a strip of your waxed paper substrate (with nothing printed on it) that is the about a half inch longer than the length of the Stouffer's step tablet (about 5") and about half an inch wide. Now coat a strip of your Platinotype as you normally do that is about 6" long and an inch and a half wide. When you expose, lay the plain negative substrate down on the coated paper strip towards one side so that you can then put the Stouffer's on top of it straddling one edge of the negative substrate. Thus you will print all the steps of the step tablet both with and without the waxed paper substrate. Expose it for close to the amount time (as a starting point) that you did with the digital negative. Develop and dry it. Then examine it. Remember you are looking for where you get a merger of two steps in the area that is exposed under both the step tablet AND your negative substrate. If steps one and two are merged, then perfect. You know your exposure value. If steps 2 & 3 are merged (seem equal in density) then you have to subtract one half stop from your exposure value....or multiply by .71 etc etc. Dick Arentz has a great explanation of this process in his book.
OK, why lap the edge of the waxed paper substrate? Because it also gives you an idea of the density of the substrate or its resistance to UV light. It also lets you compare the exposure of your substrate to what your value would be for a standard negative, assuming the same base + fog between the Stouffer's and "standard film." Given that you have determined the waxed paper substrate to have a density of about .39, you should see your black come in almost 2.5 steps apart from the area with just the step tablet on it.
If you don't have a step tablet around and you happen to have some Pictorico OHP film around, cut some strips of successively shorter lengths about half an inch wide and overlap them. Each layer is about one half stop density. This might get you by until the stores open Monday.
Hope this helps. What kind of paper and wax are you using? What adjustment curve are you using?
Good luck!
Mark Nelson
In a message dated 9/27/03 7:39:19 PM, nick@mcn.org writes:
Ok (BTW, please correct any questionable assumption made herein), I have a digital step wedge negative with a base density reading of .39 and a highlight density of 2.2 (being a complete neophyte, I might have these reversed) which equals a difference of 1.81. As Sandy kindly pointed out recently, you also have to make an small adjustment which makes this neg have a density range of approximately 1.7. As has been discussed recently, 1.7 should be a good density for a normal negative when doing PT/PD. Also, there is good separation between all the steps when viewed and tested for density on my old color analyzer, now new densitometer.
I used equal amounts of FO (freshly mixed at 27% as I have done many times) & PD (older) and a single drop of PT (which has rendered the desired color) for a total of 11 drops on a proper sized image opening. My rough calculation is .48 drops per square inch of image area on Cranes Platinotype when using a glass rod.
The resulting test print indicates that I have arrived at nearly the proper exposure because the highlights have density up to the proper point on the steps and the highlights have cleared properly. And, the black is as black as I could ask for.
On the other hand, the dark steps loose separation beginning at 30%.
Ed Stander tested this substrate and found it to have an identical association between visible and UV light blockage in the entire range - Our thanks to and a quote from Ed:
"The film blocks a proportion of received UV and Visible light equally across the board. There are no real peaks or troughs in the transmission curves. Having said this, the blockage is as follows: The waxed film blocks 1/2 of the UV falling on it, while the unwaxed film blocks 3/4 of the UV it receives. These values (amazingly enough) are nearly exact at 360 - 400 nm."
I infer from the above statement that if I use the film unwaxed, I will add a stop of exposure to my established time plus compensation for the base. In the case above, the exposure is just more than twice the length of the exposure for a Lightjet neg that I have printed successfully many times - as expected.
So, where am I? Well that's what this post is for - I don't have any real direction to follow here and I'm looking for some input.
Could the ink blockage for the UV not be linear to the visible light (my enlarger) that I used to test the density?
Could I have miscalculated the density (complete babe in the woods here) and in reality the neg is more/less contrasty than I'm thinking it is?
Could some of chemicals be outdated? Potasium Oxylate (cold bath) which as I understand it is better as it gets older (I also tried some unused), freshly mixed Ferric Oxylate and I can't believe that the EDTA has any bearing here.
Could the single drop of PT be enough to increase the contrast of the print from an already ok (read that I'm assuming a proper contrast for PT/PD) negative?
I'm sure to be embarrassed when the simple answer is arrrived at and I promise to report.
Appreciate your thoughts,
Nick
This archive was generated by hypermail 2.1.5 : 10/01/03-03:09:00 PM Z CST