Best Practices for Pt/Pd printing, and addressing commonly occurring problems

[Zero_Equals_Infinity]

I would love there to be a best practices guide on Pt/Pd printing, so that the learning curve was not quite so steep or so long.

One problem that I am dealing with is the problem of getting pure whites with the Epson 3880 printer. I have recently switched from Inkpress to Pictorico, (which is huge improvement), but I have the sense that fogging may to some extent be occurring.

So to kick off the discussion, I would like to discuss fogging, how to determine if you have it, and what to do about it.

To test for fogging I am thinking about laying down some Pt/Pd emulsion on a piece of paper, and after it dries, throwing it through the development, wash, clearing, wash cycle. I expect if fogging is an issue I will still not get a pure white.

Next, if that works, and fogging is an issue, what are the likely root causes and actions to prevent it.

I print with a single 100 watt incandescent bulb on in my workspace --- Could that me an issue?
If the water used in the wash or clearing bath is slightly alkaline would that cause it, and if so, what acid, and how much should be used per litre of solution to correct for it.

Are there any other possible / probable culprits?

Maybe an FAQ or a wiki would be a good way to insure that our respective lessons learned can be a readily accessible resource. Ideas?

 

[pschwart]

There can't be a definitive "best practice" guide since there are so many variables in work flow and environment .Everyone does their own testing to determine what works for them. There are some basics, including testing for fog and complete clearing.

A fog test is a good idea. Don't forget to use FRESH chemistry and cover part of the sensitized area. Incomplete clearing can also degrade highlights, and this test will tell you if that is a problem, too.

FYI: I have always found Inkpress to be a drop-in replacement for Pictorico. What differences are you seeing? Are you using the Epson driver (colorized or ABW?) or QTR?

 

[Zero_Equals_Infinity]

The substrate holds a higher ink load which given the lower UV opacity of the 3880 inkset is helpful. It also has no curl which means I do not have to tape it to a backing board to feed through the front-end loader of the 3880. I have had jams with the Inkpress because of curl when back-end loading, and more frequent misalignment resulting in more frustration when loading. All in all it is a much friendlier medium to work with.

I am using QTR.

I am using a fresh batch of clearing chemistry and a water rince between development and clearing as per Ron Reeder's method (4 tablespoons of EDTA and 2 of Sodium Sulfite per 4 litres of water.)

Ron recommends adding acid to the post-development, pre-clearing waterbath if the tap water is alkaline it causes ferric oxalate to be bound to the paper fibres ... and impossible to remove. I may just add some stop bath (acetic acid) to my initial water bath to insure that is not the case.

 

[pschwart]

After initial rinse, I always clear using a citric acid bath, followed by EDTA + sodium sulfite. Replace the citric acid when it takes on significant color.

 

[Zero_Equals_Infinity]

Sounds reasonable ... now to find some citric acid, or should I just start squeezing lemons ...

How much do you generally mix per liter of water?

 

[pschwart]

not critical; I use 2-3 TBSP/liter. Citric acid is cheap -- buy 5 lbs. as you will go through it quickly.

 

[PVia]

Something you don't mention is use of a restrainer. Are you using the ratio method or NA2? Oftentimes, you may get fog with no restrainer...sometimes just a hint is needed even if the neg seems to have a high density range.

 

[Zero_Equals_Infinity]

I am using the following ratio to cover 8.5 x 11 area: 1.5ml Pd / 1.5ml FeOx / .06ml NA2 (2.5%).

 

[Zero_Equals_Infinity]

The good news is the fog test came back perfect. I applied the emulsion, dried it, developed, and cleared and it was indistinguishable from clear paper. So far so good. I am also now adding citric acid to the water bath following development. (Is there any benefit to adding citric acid to the potassium oxalate developer or clearing baths to change their PH?)

I also reprinted and scanned the QTR calibration image to measure the contributions of black and yellow ink to try and figure out how to get pure white. At 100% PK on the calibration image, and scanning back into photoshop, I show a value for K = 30%, (so 70% blocking.) At 100% Y came in at around 30%, and at 50% it was a mere 7% ... so not so good.)

I found that the Pictorico film has a practical ink limit of around 155% before the negative looks smeary prior to using the hairdryer, and am changing the ration of Y and PK to see if I can find a sweet spot of maximum blocking to yield a pure white. I am also assuming some form of synergy since the amount of blocking using two inks is better than would be suggested by simply summing the contributions of each ink. (e.g. I get a measured value of K = 5% with a mix of PK = 100% and Y = 50% on my step wedge, and not the 28% that would be expected by multiplying (.30 x .93) contributions of K and Y from the calibration image. )

Note: The amount of Pt/Pd/Na2 I use tends to be a bit high to assure that it is evenly distributed over the Arches Platine. I use masking tape to frame the area to be coated, and wait about 2 minutes to assure even spreading before drying with a fan for about 5 minutes. It may be that the thicker coating that results may require both a longer dry time and contribute to the difficulty of obtaining a pure white. I will have to try a thinner coating to see if that changes anything, though thinner coatings are more susceptible to patchiness and are more sensitve to brush technique. Ah the joys of it all. FYI, I am using a Nuarc 26-1K with a mylar sheet on top of the rubber mat to reduce the moisture loss from the paper resulting from using the vacuum frame.

 

[Zero_Equals_Infinity]

One quick question: Does QTR allow use of both PK and MK at the same time, (i.e. can you edit the profile to use both blacks)?

 

[pschwart]

QTR only knows about ink channels. Each cartridge must have a chip appropriate for that printer channel, but you can fill it with whatever you like.

 

[Zero_Equals_Infinity]

Ok, so I could use a refillable system and put whatever inks I wanted to use in the containers, (including presumably rolling my own by mixing inks in a single container, and I am not averse to this idea since I don't mind dedicating a printer for making digital negatives.)

Has anyone done a calibration print in QTR for any of the refillable ink suppliers? Before going down the road of spending the money on a new set of refillables, I would like some certainty about their UV blocking characteristics.

About the rolling my own approach: I think that there are two competing aims when producing a digital negative. One is to maximize the contribution of as many channels as possible to derive a smooth tonal transition/low grain, (i.e fewer gaps from unused channels for each [360 DPI] dot printed), and the second is to have sufficient UV blocking to insure a pure white on the print. I suppose in theory, the ideal would be to have all 8 channels loaded with a composite that would be evenly distributed to control grain and provide complete UV blocking at an ink density that does not cause problems for the negative. In practice, I expect that using two composites (4 channels with one, and 4 with the other) is the practical best solution, where one composite is optimized for Dlow and the other for Dhigh. (Note I am using the terms Dlow and Dhigh in preference to Dmax and Dmin since optimizing to the furthest extremes may not be ideal in the crossover midtone region.) The Dhigh composite would need enough inkload headroom to allow for values of Dmax that are high enough to accommodate alternate processes with very wide ranges of Dmax to Dmin, (of which Pd/Pt is one of the widest), and the Dlow composite would need to allow enough inkload to be applied so as to limit graininess.

If anyone has the UV blocking specifications for refillable third party inks it would be much appreciated, as then it should be a simple matter to determine good ratios for the two composites. I am ballparking with the idea that the Dmin composite used alone would hit 100% for a negative transmission density of 35% and that the Dmax composite used alone would hit around 80% for a negative transmission density of 100% for Pd/Pt. Filling the cartridges to 5 or 10% with pure inks and using a UV densitometer on a QTR calibration negative and charting the contributions of each ink would likely enable the characteristics of each to be readily determined from which a mixture for each composite could be determined.

Any contribution to this train of thought are encouraged. I would of course eliminate zero contribution inks from even being ordered, and perhaps limit the inks in the mixture to a subset, (Y, MK, PK, LK).

 

[pschwart]

UV blocking specifications
And wouldn't it be nice if manufacturers supplied this with their inks

The goal is to achieve the required blocking + smooth tonalities while minimizing the amount of ink laid down. More ink channels can significantly complicate the profiling exercise, especially if you profile each channel instead of a group of light inks and a group of dark inks. In my experience you don't actually need 8 channels. I think my current profile uses 5. There are an infinite number of combinations and permutations. I can't think of any 3-party color inks I have tested that were good UV blockers. The Cone Piezography (monochrome) inks can provide > 4.0 so can work well. If you don't have a printer that he has profiled you can still use his ink with your own profile. Enjoy your testing