CGATS Smoother vs Dmax of Paper


Dear Walker

I am trying to do a linearization for Hahnemuhla Platinum Rag Paper, and chose 450 seconds as the standard printing time for getting maximum black (FYI, i did quite a lot of test on this and assure that 450 seconds is the right timing).

Then i printed IJM curve to print the 129 patches for linearization purpose. And the final result seems the highlight and shadow going down quite a lot and it seems it is almost not possible to get close to a 45 degree Slope curve. Please refer to attachment.

If my goal is to do a perfect linearization, what should i do…? I do keep control on all my process including sensitizer amount, brushing method, developing and clearing process.




It look to me like you are ok, though maybe a bit more exposure than necessary. The Smoother will be able to linearize this, but you might want to double check your exposure time. How did you determine the exposure time?

This is a really good example of what I referred to as “personal variables” in my reply to John Forney’s new post today. My first linearization print with the Master curve always skews too light rather than too dark.


Dear Keith

Thank you very much for your reply.

In order to get the maximum black of the paper…i first used a traditional method by covering half of the coated paper with Pictorico Ultra Premium Film, and half of the paper NOT covered with the OHP. I tested 2 times, one with 90 seconds increment,and the other one 100 seconds increment. then i discovered that 450 seconds should be the right timing since the covered blacks are almost same as uncovered black.

Then i use Stouffer 31 steps to do another 2 test, one with 450 seconds exposure and one with 400 seconds (i know 400 seconds is not 1/3 of a stop, but since my first 90 seconds increment test told me that 360 seconds does not work).

I am working on the second linearization tonight, and is now waiting for the paper to dry throughly until tomorrow afternoon…and i will show you the final results.

AGAIN…thank you so much Keith and you are always the first one reply my post.!!! : )

PS> i encountered another problem of the Hahnemuhle paper— it seems the coated area without image leaves a layer of light grey onto the paper…it does not happen on Berggar paper… should i use a stronger Disodium EDTA??? any recommendations? and…do you think it may be because my UV machine is too powerful? 5000Watts HID



Sounds like your exposure time is close enough, even if not perfect. The problem with using increments of equal time is that the higher you go the less difference there is between adjacent steps, and it becomes difficult to see a difference. 90 + 90 is a full stop, but 180 + 90 is half a stop, 270 + 90 is 1/3 stop, 360 +90 is 1/4 stop, …. You see the problem. That gets you in the ballpark, but once you know that it is somewhere between let’s say 360 and 450, you need to test that range with more precise increments. Try 360/375/395/420/450, or something like that. It’s also a good idea to go over, so maybe add 500 to the series.

Then use the Stouffer to verify, but don’t forget that base density is slightly different.

Most people have found the Hahnemuhle Pt Rag to clear easily. We tend to use tetra EDTA on this side of the world, I think because it is easier to obtain. My clearing bath formula is 1 tablespoon (I know, not very precise!) EDTA + 1 tablespoon Citric Acid per liter of water. Sometimes I add a bit (1tbsp or less) of Sodium Sulfite, depending on the paper. A chemist told me long ago that mixed in that order, the citric acid converts the EDTA to the disodium form.

Can you post a picture of the a print with the light gray. That sounds like fog, and is probably affecting your highlights.



Dear Keith

Thank you so much for your fast response.

I do notice that the Stouffer film’s density is not same as what we do on PiezoDN, so i just use it as a reference. BUT one thing maybe worth sharing with you… i don’t know whether it is right or wrong…

there is a formula i read from a book call “Easy Digital Negative”, and +1/3 of a stop or - 1/3 of a stop is not like what you’ve mentioned. there should be a formula… i will take a photo tomorrow and share with you…

my clearing procedure is same as Dr Mike Ware:

10 mintues disodium EDTA (to clear the iron/yellow color faster…acidic Ph3-4)

10 minutes Kodak Hypo Clear (alkaline…)

10 minutes TetraSodium EDTA (alkaline …best for archival purpose)

30 minutes running water…

I learn that from

this process works great on Berggar…but on Hahnehmuhla platinum Rag…it seems not working…very well

so…do you think there is a relationship with my super power UV exposure unit? 5000 watt HID point light source…or i should increase the disodium ETDA % from 5% to 10 or even more??? i just don’t wanna hurt the paper too much.

I will take a photo and share with you tomorrow (china timezone here)



I’d like to see the formula, but for all practical purposes it is pretty simple. Doubling the time increases exposure by one full stop. Likewise, halving the time decreases exposure by one full stop. You can easily figure out fractional increments from that. Keep in mind that with the fairly lengthy exposure times we are using, a change of 10 seconds, more or less, is unlikely to be noticeable.

I won’t argue with anything Dr. Ware recommends, but I will say that Kodak Hypo Clear is mostly sodium sulfite with some sodium metabisufite, and a bit of sodium citrate and … (wait for it) … tetra EDTA. It is actually from this that formulas like mine were derived.

Since you said that you are getting areas of light gray, rather than yellow, I am thinking that your highlights are overexposing. Gray is fog from exposure; yellow is stain from incomplete clearing. No amount of increased clearing will remove fog. As my mentor Dick Arentz would say: Fog is archival, stain is not. If I am correct, the solution will be to increase the contrast of your coating solution (by whatever method you prefer) in small increments until the fog is gone. Another thought is that you might need to check your ink limits. It may somehow be set too low, though that seems odd for Pt/Pd since the IJM Master curves were made for this process. At any rate, you should get this resolved before doing any more linearizations since it will effect the outcome.



Dear Keith

AS promised, please find attached photo with the formula i get from a book called “The Platinum Printing Workshop” by Ian Leake. please review and give me some comments…YES…you are absolutely right 5 to 10 seconds means nothing to alternative printing.

AND…please also find the problem of my print currently using Hahnemuhle paper… you will see the fog around the 129 patches print out…

I am going to do a test tonight…minimize the lighting condition…use a newly produced potassium oxalate and disodium EDTA…and i will tell you the results later.




Dear Keith

I just did another 129 patches print using freshly made potassium oxalate, disodium EDTA, Hypo…Tetrasodium EDTA…but the results are the same as before…

just minor difference… then check my old print out and discovered that almost all my prints have “slight fog” around the edge of the coated area.

YES…it affects my highlights and also my linearization. of coz I won’t see it when it comes to real prints (i mean the fog edges), but since it affect the highlights…i am very unhappy about it…

So…any possible solution on this???

Do you think the problem arise because of the following?

  1. The 5000Watts UV exposure unit (too strong?)

  2. my sensitizing solution??? i mixed it myself…all Fe, Pd, Pt…

  3. My tungsten lightbulb…? (should be ok)…

  4. tween 20…10%? should not be i freshly made it…




You need to use a small amount of NA-2.


Also, the next release will include an updated 7900-9900 “bullet-proof” master curve with an Optical density over 3.5 and a UV density over 6.





Here is a beta curve built for 5000k plate-makers and POP (print out process) palladium printing on the 7900-9900






Dear Keith and Walker

thank you very much for your reply. I guess i have no choice but have to use some Na2 as sensitizer…!! I never use it before even though i have it in my cabinet…

Keith…NOW i know what you are talking about in the previous Forum Messages… Originally, i thought PiezoDN can 100% control the tone and contrast which make me think i do not need to use any Na2.

I will do all linearization process AGAIN by using some Na2 for both Berggar and Hahnemuhle paper…let’s see whether the issue can be resolved…

I am sure both of you know it is NOT interesting to REDO linearization coz it takes a lot of time…but i will keep up with it and achieve good results…




Dear Walker

I have tried to use Na2 already…YES…the fog gone away!!

Question: if i use 80Pd20Pt…but my platinum solution is traditional solution and NOT Na2…can i use the Na2 if i discovered a little bit of fog??? Otherwise…what should i do?

Should i use Ferric Oxalate contrast agent???



Dear Walker and Keith

Please find attached the fine edge D-max test paper…

Walker as you said for palladium…i only used 1 drop of 5% Na2 on a 8x10 paper…and the fog goes away…thank you!

Please refer to attached photo : )

Please answer the previous post question if you can.



Dear Keith

Thank you so much for your answers… it seems that if i want to do platinum palladium prints…i have no choice but have to use FO-A and FO-B method…thank you…

I will try to mix some different ratio of FO-A and FO-B and see how much i will need in order to avoid fogging.

i just finish my test and home 15 minutes ago…finally…after another D-max test with 300 seconds as base…and 20 seconds increment…finally i choose 340 seconds as the standard exposure time, and the linearization curve seems ok to me…at least it is not a U-shape curve and already quite close to the “standard line” as provided by PiezoDN smoother tool.

The second paper is Hahnemuhle paper…with 2 drops of tween 20. same proportion like yesterday but it seems it is not as good as yesterday test…maybe because of my coating techniques… :slight_smile:

I am going to do the second linearization and ICC tomorrow…lets see how it goes…




Dear Keith

I almost finished my linearization by using Na2…as you may expect…the Na2 maybe too strong that wash out my highlights… i am using 5% solution now.

Is it ok to use distill water to dilute the 5% to 2.5% or 1.25%…?? Just use distill water right?

please advice.



Yes, 5% is too strong for this image size and solution volume. 1.25% should be sufficient.

Here is what I recommend to make 2.5% and 1.25% Na2 solutions. You will need 2 small bottles ~ 30ml. I am assuming you are starting with a 25ml bottle of 5% Na2. You may want to alter the amounts if you are starting with less.

  1. Draw 12ml of 5% Na2 and transfer it to an empty bottle.
  2. Add 12ml distilled water.
  3. You now have 24ml of 2.5% Na2. (And 15ml of 5% remaining.)
  4. Transfer 8ml of the 2.5% Na2 to the other empty bottle.
  5. Add 8ml distilled water.
  6. You now have 16ml of 1.25% Na2, 16ml of 2.5%, and 15ml of 5%.


Dear All

It seems the use of Na2 blown up some of my highlight area of the 129 patches…according to the CGATs data/curve from the smoother tool… even though i did another linearization in the hope that the “highlight washout” may disappear…

It seems the 5% solution of Na2 from B&S is too strong for my case…so…just want to as k should i dilute the current 5% solution in 2.5% just by pouring more distill water into the solution…5% 10 ml to add another 10ml to make the solution into 2.5%… ?

Anyone knows whether the solution from B&S is stock solution or working solution??? is that ok to just dilute it by using distill water?



Dear Keith

I just discovered that you’ve covered how to dilute the 20% Na2 in your website… many thanks!!!

PS> but can i dilute my existing 5% Na2 from B&S?



Dear Keith

Thank you very much for your answers!! THANKS A MILLION!!

I guess i can do a better job on 129 patches linearization tomorrow :slight_smile:

I will use my existing 10ml 5% Na2 to do the dilution as above first, and order some from B&S tomorrow.




Harris - Please see my previous message(s).

It is both stock solution and working solution depending on the strength you need which varies depending on the print size and solution volume that you are using.

All of the following are equivalent in terms of the strength of Na2 to volume of solution:

  • 1 drop of 0.6125% Na2 in 1ml of solution (0.5ml FO + 0.5ml Pd)
  • 1 drop of 1.25% Na2 in 2ml of solution (1ml FO + 1ml Pd)
  • 1 drop of 2.5% Na2 in 4ml of solution (2ml FO + 2ml Pd)
  • 1 drop of 5% Na2 in 8ml of solution (4ml FO + 4ml Pd)
With digital negatives we want to use the minimum amount that keeps the highlight free of fog without increasing contrast. My tests, repeated many times over many years always with the same result, have shown that this minimum effective amount of Na2 actually extends the tonal scale by 0.05 - 0.1 density over not using any Na2. This is counterintuitive, we would expect no Na2 to have a slightly longer tonal scale, but my test have shown otherwise. This is why I prefer to uses it even if it is not necessary to prevent fog. It is a personal choice in my case. In any case, all of these personal process choices must be decided upon before linearizing because most if not all of them have some effect on the linearization. If you change something in your processing chances are good that you will need to relinearize.

I just saw your message where you say you have 10ml of 5% Na2. So still follow my directions on how to make the other dilutions in my previous message but start by transfering 5ml of your 5% Na2 to an empty bottle and add 5ml distilled water to make 10ml of 2.5%. Then transfer 3ml of that to another empty bottle and add an equal amount of distilled water to make 1.25%.

Hope this all makes sense.