Pyrocat-HD Negatives & Alt Processes

[Andrew O'Neill]

Made some Van dykes yesterday for the first time. I exposed a few 8x10 negs that had been developed in Pyrocat-HD. The exposures were about an hour long as apposed to 10 to 15 minutes for the conventionally developed negs that I also exposed. Obviously the stain on the P-HD negs made the exposure much longer. The Pyrocat-HD negatives also looks much much nicer to my eye.
Am I right in saying that the stain slows down exposure times?

[Brian Ellis]

I used to print quite a lot with van dyke brown, I never had exposure times anywhere near an hour. I used D76 mostly but also some PMK. While others who actually use pyrocat-HD obviously are in a better position to know approximate times than I am, it's difficult to believe that an hour is normal. I'd think something is wrong somewhere, maybe in how you coated the paper, maybe in the exposure, maybe in the development. IIRC my times were in the 10 minute ballpark with D76 and PMK even with a negative developed specifially for van dyke brown (i.e. a greater density range than normal).

[sanking]

Made some Van dykes yesterday for the first time. I exposed a few 8x10 negs that had been developed in Pyrocat-HD. The exposures were about an hour long as apposed to 10 to 15 minutes for the conventionally developed negs that I also exposed. Obviously the stain on the P-HD negs made the exposure much longer. The Pyrocat-HD negatives also looks much much nicer to my eye.
Am I right in saying that the stain slows down exposure times?


Exposure in alternative printing as in regular silver printing is based on shadow density. Since stain is proportional, i.e. least in the shadows and greatest in the highlights, it follows that stain would increase exposures only as much as the general (B+F) stain is increased in the shadows. One expects some slight increase, maybe about 1/2 stop in printing UV sensitive processes with stained negatives, but not two full stops. An increase in printing time of two full stops clearly indicates over-exposure.

Sandy King

[Ken Lee]

Sounds like your light source may be weak. Mine take only 2-4 minutes to cook.

I got mine from Edwards Enginieering here (http://eepjon.com/index.htm).

[j.e.simmons]

I use the spiral BLB bulbs for exposure of my Van Dykes and salt prints with Pyrocat negatives. My exposure times are in the 10-20 minute range.
juan

[sanking]

Sounds like your light source may be weak. Mine take only 2-4 minutes to cook.

I got mine from Edwards Enginieering here (http://eepjon.com/index.htm).

Printing times vary quite a bit with the iron processes depending on sensitizer mix and humidity, but my typical times for printing with developing out Pt./Pd. are in the 3-5 minute range with a bank of BL tubes and 1-2 minutes with the AmerGraph ULF-28. This is for well-exposed and developed negatives. Generally I find that most people are using UV exposure units that print in the 4-8 minute range.

Overexposure must be avoided at all costs with alternative printing since the minimum printing time is already so long. Many people overexpose negatives meant for alternative printing since the literature tells them that they need a stout negative with a lot of contrast. It is true that a negative with a lot of contrasty is needed, but a negative meant for alterantive printing should not have more density in the shadows than one intended for silver printing. Another issue is that the high contrast range to which negatives must be developed for printing with alternative processes results in much higher effective film speed. For example, when exposing negatives for Pt/Pd. printing I use an EFS of 800, double the nominal rating.



Sandy King

[j.e.simmons]

Sandy, do you do BTZS paper testing for your alt process materials as is described for silver paper - make a step wedge print and read the density in the same way? Or is there a difference with alt processes?
juan

[sanking]

Sandy, do you do BTZS paper testing for your alt process materials as is described for silver paper - make a step wedge print and read the density in the same way? Or is there a difference with alt processes?
juan


The principle is the same for alternative materials as for silver paper so one could work the way you describe. But this procedure is only valid if you are printing with non-stained negatives since a stained negative will not print the same as a Stouffer step wedge

But I don't work that way. By the time I started using BTZS I had already been working with alternative processes for almost fifteen years so I knew what kind of negative I needed. From experience I know the exposure scale of the alternative processes that I work with, and how to move it up or down slightly if necessary. Therefore, all I really need to know is how to develop my negatives so that their DR correponds to the ES of the process. I use BTZS type testing with films and developers to determine what type of development is needed with a given film/developer combination to achieve the desired DR. Generally I aim for a DR of about 1.85, which allows me to print easily with kallitype, straight palladium and carbon with a minimum of contrast control during printing. Of course, the negative DR must be read with a densitometer that has a UV mode since neithr the Visual nor Blue mode sees exactly how the stain prints.


Sandy King

[Eric_Scott]

Sandy,

With a DR of 1.85, what is your typical diffuse highlight density? What is your typical fb+f level?

Just curious, as for me, I need 20 minutes with florescent tubes for carbon negatives with diffuse highlight density of around 2.00 and fb+f of .08. These are Tmax400 negs developed in D-76.

Eric.

[sanking]

Sandy,

With a DR of 1.85, what is your typical diffuse highlight density? What is your typical fb+f level?

Just curious, as for me, I need 20 minutes with florescent tubes for carbon negatives with diffuse highlight density of around 2.00 and fb+f of .08. These are Tmax400 negs developed in D-76.

Eric.


The DR of textured highlight density is around log 1.70. Printing time with carbon, as with Pt./Pd. and silver papers, is determined by shadow density at Zone 1 or 2, not by highlight density. As you know, we adjust the strength of the dichromate sensitizer to control highlight contrast.

For a FB+F of 0.08, which is very low, your time of twenty minutes seems about right, assuming you are making a very thick tissue. Sensitivity of carbon tissue can vary tremendously according to how thick you make the tissue. The carbon tissue from B&S, which is very thin, is very, very fast -- prints in about 60-80 seconds. However, the tissue I make is very thick and may take twenty or more minutes of exposure. Just by comparison, the dry height of the emulsion on the B&S tissue is less than 0.2 mm, whereas the dry height of my tissue is on the order of 1.0 mm.

Of course, the purpose of the thick tissue is to give high relief on the print.

Sandy

[Eric_Scott]

Printing time with carbon, as with Pt./Pd. and silver papers, is determined by shadow density at Zone 1 or 2, not by highlight density. As you know, we adjust the strength of the dichromate sensitizer to control highlight contrast.
Sandy

I kid you not Sandy, I didn't know this. I've been doing just the opposite. I've simply been lucky up to this point. Now I'm going to use the procedure you describe. I'm an idiot.:eek:

Eric.

[sanking]

I kid you not Sandy, I didn't know this. I've been doing just the opposite. I've simply been lucky up to this point. Now I'm going to use the procedure you describe. I'm an idiot.:eek:

Eric.

Eric,

In carbon printing contrast is controlled by matching the strength of the sensitizer to the DR (density range) of the negatives: strong sensitizers are needed for contrasty negatives (those with high DR), weak sensitizers for negatives of low contrast (those with low DR). The strength of the sensitizer is expressed as a percent solution, an expression of weight per volume (w/v), indicating how many grams of a chemical are to be dissolved in 100ml of water. For example, to prepare a 3% ammonium or potassium dichromate sensitizer dissolve 3 grams of the dichromate in 100ml of water (or 30 grams in 1000ml of water, etc.).
The same principle applies for both tray and spirit sensitizing, though the mechanics of the two methods are quite different. I use potassium dichromate with tray sensitizing, ammonium dichromate with spirit sensitizing. In recent years I have been using spirit sensitizing more and more.

Adjusting the strength of the dichromate is not the only way to control contrast if you make your own tissue. You can also adjust contrast by varyng the amount of pigment in the tissue. I do that also, but adjusting the strength of the dichromate is something that works with all tissues, regardless of the inherent contrast, and this is something that is pretty much essential in working with in-camera negatives, regardless of whether they were developed with staining or non-staining developers.

Sandy King

[Eric_Scott]

Sandy -

I hijacked this thread. We should be discussing this at the carbon list. I knew that sensitizer strength controlled contrast. What I didn't know was that I was supposed to base exposure on the shadows, not the highlights. I base exposure on the highlights, using sensitizer strength to control the shadows. It seems to work, but I must confess, I try hard to produce negatives that don't require adjustment from my standard strength of 2% potassium dichromate. Therefore, I don't have much experience with contrast control.

Eric.

[sanking]

Sandy -

I hijacked this thread. We should be discussing this at the carbon list. I knew that sensitizer strength controlled contrast. What I didn't know was that I was supposed to base exposure on the shadows, not the highlights. I base exposure on the highlights, using sensitizer strength to control the shadows. It seems to work, but I must confess, I try hard to produce negatives that don't require adjustment from my standard strength of 2% potassium dichromate. Therefore, I don't have much experience with contrast control.

Eric.

OK, I misunderstood what you meant.

The carbon list has been very quiet recently, but by coincidence Howard Efner just posted a message there this evening to which I responded.

Anyway, I don't belive this is too much off-topic because people using in-camera staining negatives must use some type of contrast control, and the original message that started the thread was about printing with an alternative process.

However, whether silver, Pt/Pd or carbon, time of exposure is determined by shadow density at Zone 1, II or III. Then we apply contrast controls (filters with VC papers, dichromate or Na2 with palladium, or dichromate with carbon) to match the DR of the negative to the ES of the paper. Same principle for all of these processes. Of course, the contrast controls may also have some secondary impact on exposure, so a second range of adjustment may be necessary.

I would suggest that you experiment in carbon with a Stouffer step wedge. Sensitizer four or five sheets of carbon tissue with different strength sensitizers, expose them all for the same time, and then develop. The effect of sensitzer strengh on ES will be immediatley obvious, as it would be in using different VC filters in printing with VC silver papers.

Sandy King

[Andrew O'Neill]

It looks like I'll have to do a lot of experimenting...I have a good densitometre, but cannot measure the stain with it. I know that my negatives have a fairly long DR. I don't over exposure the negatives but rather develop a little longer.
The exposure time in the UV box (and it's a very strong one with BL tubes) was about an hour. The print looked lovely...I just don't want to have to wait that long.
Does anyone know if there is a way to make the Kalitype emulsion more sensitive to exposures?

[Eric_Scott]

OK, I misunderstood what you meant.
However, whether silver, Pt/Pd or carbon, time of exposure is determined by shadow density at Zone 1, II or III. Then we apply contrast controls (filters with VC papers, dichromate or Na2 with palladium, or dichromate with carbon) to match the DR of the negative to the ES of the paper. Same principle for all of these processes. Of course, the contrast controls may also have some secondary impact on exposure, so a second range of adjustment may be necessary.

I would suggest that you experiment in carbon with a Stouffer step wedge. Sensitizer four or five sheets of carbon tissue with different strength sensitizers, expose them all for the same time, and then develop. The effect of sensitzer strengh on ES will be immediatley obvious, as it would be in using different VC filters in printing with VC silver papers.

Sandy King

I learned to print silver from books. Every book I read told me to base exposure on the highlights, controlling the shadows with paper grade. The only book I read that said differently was a book by Fred Picker, who said to base exposure on the shadows, controlling highlights with paper grade. I have no idea what the correct method is, but the former method has worked for me in silver.

I have experimented with Stouffer step wedges in carbon. I'd like to continue this discussion and share my experiences, but my carbon tissue/watercolor paper sandwich is now ready for the hot water development.

Eric.

[Paul Giblin]

Andrew,

You don't say what film you are using, what dilution of Pyrocat, agitation method, EFS, etc. you are using. I point this out not to be critical, but because it would be useful info in the diagnosis of your printing time problems. You may well be overexposing your film and not know it.

I say this as a recovering overexposer/overdeveloper. I know from experience with kallitype printing (which is mostly what I do, though not necessarily well) that a negative that looks great when held up to the light can be too dense and/or too contrasty to print well (or quickly).

I have a fairly weak bank of flourescent tubes and I know from experience that anything that takes longer than 30 minutes to print is generally not worth further effort, at least using my system. Those negatives will have to wait until the day I tackle salt prints or albumen.

I also know from personal experience that excessive agitation during processing increases general stain enough that printing times can become too long. You can print through it if the negative's contrast is right for the process, but you will have to wait a long time.

Just a few thoughts.

-Paul

[Andrew O'Neill]

HP5+ (2+2+100) tube. EI 250.

[Paul Giblin]

Not sure. I suppose you could try rating it at 400 and see what happens. If your print looks good, it may just be extra overall stain that is adding to your print time.