darkroom humidity

Discussion in 'Alternative Processes' started by philsweeney, Feb 14, 2004.

  1. philsweeney

    philsweeney Member

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    still trying to improve my kallitypes. working on one possible problem at at time. the humidity in my darkroom was low so I got a humidifier. running on high for appx 10 hours its up to about 50% from 35%. I have also hung some papers so they can acclimate to that humidity. Curious what others do? Can I just run the humidifier a couple of days in advance of printing? I usually do all my kallitype printing on the weekends. for the most part it seems my papers are sucking up the coatings and I am using papers others have had good results with. If I try any sizing, the arrowroot starch sounds easy whereas the gelatin methods are more elaborate and scary! I have already tried a little PVA under the drier conditions with minor improvement. BTW I am experimenting with negatives that require 4ml of dichromate to 1 liter of sodium citrate, so I believe neg range is not a big issue although I intend to increase the neg range in a few for further prints.
     
  2. lallan

    lallan Member

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    For Pt/Pd printing (I have not tried Kallitype), I have one small humidifier and one 'room' size humidifier. I fill the sink with warm water, turn both humidifiers on, turn a small fan on and go have coffee. The darkroom, 6x12 foot, goes from 28% to 50% in about an hour. When I was printing ziatypes (which need a lot of humidity), I would turn on the shower in the bathroom for about 20 minutes so the room was good and steamy, hang the paper and let it be for around 20-30 minutes. Do you have a large room? 10 hours is a long time!
     
  3. Jorge

    Jorge Inactive

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    Phil, perhaps you would get better results using potassium oxalate as the developer if you are using the restrainer in the developer.
     
  4. philsweeney

    philsweeney Member

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    thanks, for the help

    lallan, yes my darkroom is fairly large. I did print this weekend with better results. I can tell my paper is not sucking up the coating as fast, since I put the humidifier in the room.

    jorge, I am using dichromate. I thought about p.o. But I thought that might only change the image color?
     
  5. Jorge

    Jorge Inactive

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    Phil, on the technical side, PO will give greater printing speed. On the personal side, I developed both pt/pd and Kallitypes in both PO and ammonim citrate and found that the PO developed prints had better "depth" and a smoother tonality.

    I then proceeded to try and mix PO and ammonium citrate in different ratios to see if I could gain the speed and depth of PO and the cooler tones of the citrate and found that there was no in between, the prints with one or the other developer were better than those with the mix.

    IMO this is specially true with Cranes platinotype, the prints made with this paper and developed with citrate were rather weak and drab.....nothing like the prints I am getting with PO and socorro paper.

    As I told you, alt printing is very "personal", Arentz gets glowing prints with platinotype, I just cant no matter what I do.....
     
  6. sanking

    sanking Restricted Access

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    To further emphasize Jorge's point that alt printing is very personal, I get the same depth and tonality with sodium citrate as with potassium oxalate. Potassium oxalate at a given percentage (20-25%) has more capacity before it requires replenishing, and it is easier to decant since the development byproducts settle to the bottom. On the other hand, sodium citrate is a lot less expensive so it costs less to replenish, and less in the long run.



    Sandy
     
  7. philsweeney

    philsweeney Member

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    thanks Sandy and Jorge, I did notice the p.o. is more expensive. So far I have used the sodium citrate. I put a larger humidifier in the room so I can get the humidity up to 60%. I would like to try to cut the clearing time a little. Using the 3% citric acid solution I have been clearing for 4 minutes. I have not had any stain on the unexposed coating so I thought I would try reducing to 3 minutes. How will I know when the clearing time is inadequate?
     
  8. sanking

    sanking Restricted Access

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    Adequate clearing will be indicated by the fact that there is absolutely no stain left in the areas of the paper that were sensitized but that received no exposure. If there is any stain at all your clearing was inadequate. Fogging could also cause stain but assuming that you are drying your sensitized paper in the dark, or in very low light, this should not be a problem.

    For a more methodical approach see the section on how to verify clearing at Jeffrey Mathiias' site. H

    Sandy King
     
  9. Michael Mutmansky

    Michael Mutmansky Member

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    Phil,

    I haven't priced either chemical recently, but it is a simple matter to make PO from oxalic acid, potassium hydroxide, and H2O. Both of the components can be had fairly cheaply on their own.

    For example, check out:

    http://chemistrystore.com/

    for prices of the composite chemicals.

    I mix my own in several gallon batches every so often. It is much cheaper through that route. Last time I ordered, I got about 25# of each chemical. I also use the oxalic for other things, so it was not really an issue to have it on hand.


    ---Michael
     
  10. philsweeney

    philsweeney Member

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    Michael: thanks, would you post the recipe for mixing these to make the PO?

    Sandy, I read the article on clearing, but the second part totally lost me! Can you help me with the second part of the clearing test? It seems there are some steps missing that are implicit for the more experienced. My current processing is: 8 minutes development and there already is no stain on the unexposed coating. So I wanted to figure the shortest clearing time to reduce the bleaching in the citric acid.
     
  11. sanking

    sanking Restricted Access

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    As a general rule I recommend a minimum clearing time of about four minutes in a 3% citric acid solution. If your paper is already completely clear after development (and this is a very good thing) it would probably be safe to reduce clearing time in the citric acid from four to two minutes. Or, you could continue to clear for four minutes and reduce the strength of the citric acid solution to 2%. Either procedure will result in less bleaching of the image.

    Sandy
     
  12. Michael Mutmansky

    Michael Mutmansky Member

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    Phil,

    This is the procedure that I was given by Carl Weese a few years ago:

    Put two liters of cold water in a large bucket. Stir in 600 grams of oxalic.
    Don't worry about dissolving. Measure an equal amount of potassium hydroxide and very slowly add. The mixture will bubble up lots of CO2 and get real hot when the second ingredient is added. Next, use Ph test paper to
    check the solution. You want dead neutral. Add tiny amounts of either acid
    or alkalie until it's neutral. This is the only tricky part--amazingly small
    amounts shift the solution from acid to base and it will take a while to
    find exact neutral.

    Let me add a few notes to the description above. This will make a solution that is about 25%. I believe saturation is around 30%, so you may run into issues wit material falling out if you get too close. Just add more water. In most cases, the saturation of PO is not critical for developing, so this should not be an issue.

    Definately use COLD water, as the reaction makes a lot of heat. Also, use distilled water to avoid contaminants. For pt/pd, I make the solution pH neutral, and then add a little more oxalic, because the pt/pd chemicals are quite adverse to a basic solution, and I want to make sure that the error is on the side of acidic.

    Also note that The Chemistry Store has great prices on citric acid, sodium sulfite, and a handfull of other useful alt chemicals.


    ---Michael
     
  13. philsweeney

    philsweeney Member

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    Thanks Michael and Sandy. Michael, I have the recipe in my notes now.
     
  14. sanking

    sanking Restricted Access

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    I want to also thank Michael for the information about mixing potassium oxalate, and for the link to the Chemistry Store. Sounds like a good resource.

    A couple more notes about sodium citrate and potassium oxalate. With kallitype there is virtually no difference between the two developers so far as I have observed. When the image is toned with gold, palladium or platinum both developers give the same tone and image color regardless of developer temperature.

    With palladium there is some difference in results because if you use potassium oxalate at a very warm temperature the color of the print becomes much warmer. With sodium citrate the look is almost identical regardless of whether you use the developer warm or at room temperature.

    BTW, it is also possible to save money by mixing your own sodium citrate, using sodium carbonate and citric acid. However, since sodium citrate is already fairly inexpensive I have never bothered to make the mix.

    Sandy
     
  15. Michael Mutmansky

    Michael Mutmansky Member

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    Folks,

    There is one other thing about mixing PO that you may want to know. I have mixed up batches a half dozen times in the last year and a half or so, and I noticed that I got a slightly cloudy solution when I changed chemical suppliers a while ago.

    It appears that one of the component chemicals is not absolutely pure, and there is a slight brownish look to the solution. PO should look totally clear in solution.

    I have used the PO without any problems for pt/pd printing, however the contamination could be an issue in another process. It is too fine to filter with a coffee filter, but a student grade filter will remove it.

    I made a handful of filtering cylinders out of old plastic wide mouth bottles, by drilling holes in the lid, and cutting the bottom off the bottle. I screw the filter paper in the lid, invert in a tray and fill with the PO. It slowly dribbles through the paper and the residue that is left behind looks like an iron product.

    Anyway, I don't think it is necessary to filter it, but you can if you want to start with clear PO. I suspect that if you started with reagent grade chemicals, there would not be a need for the filtering.

    ---Michael