Gum prints and humidity

[Xandros]

Hi all,

i'm a fairly new gum printer and have been mostly experimenting different papers, combinations and techniques for now.

I am trying to write down everything as much as possible to be able to get consistent results, but somehow in april after a successful set of prints and a two-weeks holiday, I wasn't able to produce a single print worth keeping. Everything was going wrong (either way all of the emulsion was dissolving or almost none, during development). I didnt change the kind of gum, nor its concentration, nor the paper, nor the exposure distance / times, negatives, pigment, everything was the same !

Then I found a mention about ambient humidity having a huge impact on printing results on Katharine Thayer's website. So I decided to wait until the weather and air gets not so dry to resume printing.

Strangely however, now that humidity is almost back at the april's level, I'm still getting 3/4 of bad prints, and very inconsistent results from print to print ...

What could cause such a situation ?...

 

[Katharine Thayer]

Xandros, I take it you live somewhere where it's drier in the summer than in the spring and fall? Do you have a way of measuring the ambient humidity?

If you're really not changing anything from print to print, the results should be consistent from print to print; the fact that you're getting very inconsistent results suggests that perhaps everything isn't remaining constant from print to print. If you're getting inconsistent results on the same day, in roughly the same ambient conditions, it's unlikely that it's humidity that's the problem; I'd start looking elsewhere. The problem you describe, "either all of the emulsion was dissolving or almost none, during development" suggests erratic exposures; what's your light source?

It can be frustrating when things aren't going right, but working carefully, changing one variable at a time and taking notes, should quickly lead to a more consistent practice. Good luck,
Katharine

 

[Jon Harwood]

Hi Xandros,

First, I agree with Katharine she really knows what she is talking about. I, on the other hand am a Gum newcomer with about ten months experience. At the beginning of my gum work I found myself often experiencing what you are, that is I kept very careful records, I tried to change only one variable at a time and despite my most careful working methods the process often seemed unmanageable. As I struggled along month after month patterns slowly did begin to emerge and I slowly grasped the "dance of the variables" that Katharine refers to. What I kept in mind was that other people are making nice gum prints and eventually I should be able to also. It seemed to take forever, but through experience and much practice, careful note taking and by changing only one variable at a time I am now beginning to get the prints I had hoped to .

I don't know if humidity is the key issue with your prints or not. It may not be. Still, I can tell you what I do about humidity. I obtained a sling psychrometer. It is a old fashioned but reliable way to test humidity in the room you are working in. I test and record the humidity each time I print. In my workroom my baseline humidity was 65%. Through experience I found that for each addition or subtraction of 20% humidity I add or subtract one stop worth of exposure. So if the humidity is 45% I add one stop worth of exposure, making a three minute exposure six minutes.

Unfortunately I can not say that what I am doing will work for you. My results only apply to my workflow in my geographic location. You will have to observe your own results to see if my experience is applicable to your situation.

Ultimately my advice is quite the same as Katharine's. The only thing I might add would be that it is really hard to learn to make gum prints but gum eventually does reveal its secrets to those who pursue it. The reward is being able to make one of the most subtle and beautiful kinds of photographs ever invented. Good luck!

 

[Loris Medici]

Xandros, listen to Katharine -> if you're getting inconsistency the same day (w/o major climate change), then probably it's not about humidity...

OTOH, just for the records, if you want to eliminate humidity parameter from your workflow you can do like I do:
Coat, wait 5 minutes, dry with a hair dryer (be gentle, dry on low heat just until the surface isn't tacky anymore, not more), then humidify using an ultrasonic humidifier. (Mind to be consistent on your humidification ritual!) You'll get very consistent results all year round...

 

[Xandros]

Thanks for your answer Katharine. I learned a lot of what I know so far on your website, btw.

Anyway, the thing is, I kept ALL variable exactly the same. They worked for 2 different negatives, then 2 weeks later one of those negatives almost all the time seems underexposed (all washes out) and the other overexposed. It's a a bit inconcsistent but generally speaking i'm getting the same king of bad result for each negative.

I bought an electronic hygrometer and fond out that even though i'm in Belgium (quite wet overall), the humidity can drop from 70% when it's very rainy for a few days to about 35% when it's sunny for a week ...

I maybe could do a series of tests to build a humidity / exposure curve ?... dunno if it's worthwile.

I also experienced different behaviour when the sizing has been done at high humidity level or low level, not only exposure. Looks like when humidity is low, the gelatin sizing does not have the time to soak into the paper's fibers and just dries at the surface, and it doesn't work so well for printing afterwards...

 

[Loris Medici]

...
I maybe could do a series of tests to build a humidity / exposure curve ?... dunno if it's worthwile.
...

You don't seem to have noticed my description about how you can rule out the humidity parameter from your workflow??? It's not worthwhile if you work as I describe before; the moisture level in paper / exposure times will be always comparable with that method.

...
I also experienced different behaviour when the sizing has been done at high humidity level or low level, not only exposure. Looks like when humidity is low, the gelatin sizing does not have the time to soak into the paper's fibers and just dries at the surface, and it doesn't work so well for printing afterwards...
...

Do you work the sizing "in" the paper with a brush? I have sized in every possible indoor environment in my place (from 18C/30% to 28C/60%, BTW please note that RH figure isn't enough to tell us the absolute moisture content of air unless stated along with temperature...) and never noticed any, again any, difference in results. I use a "foam brush" and "work the sizing in the paper" brushing the "hot" (50C) gelatin sizing many times in perpendicular orientation. (Total operation time for 11x15" paper 30-45secs.) 50C temperature isn't a problem as long as you use the sizing solution (with hardener) one-shot as I do; normally gelatin will loose gelling strength if rehated to above 40C several times... Using extra hot gelatin solution "once/one shot" doesn't give my any problems. (= Clean prints, no staining.)

Hope this helps,
Loris.

 

[Xandros]

thanks Loris.

I don't have an ultrasonic moisturizer, and bying one in a country with 300 days a year without clear sunlight ...

Anyway, yep I got your technique to rule out this parameter !

I'm using a foam brush too, gently. Also one-shot gelatin mixture. I tried mixing the hardener in the mixture, or applying it in a separate layer after the gelatin dries, it doenst seem to change the result. As for the temperature, the problem is that I didnt have that thermometer/hygrometer at the time it worked fine, so I really have no clue ... the dryest days when it didnt work were like 28°C / 35%.

Compared to your temp/humidity examples its vice versa here, high temp means less humidity.

 

[Loris Medici]

...
I don't have an ultrasonic moisturizer, and bying one in a country with 300 days a year without clear sunlight ...
...

Well, here in Istanbul a simple model (Made in PRC) will cost something like 20EUR, so it isn't a big investment.

...
Compared to your temp/humidity examples its vice versa here, high temp means less humidity.
...

I was trying to say that high temperature/less RH doesn't always mean that the actual moisture content in the air is less then low tempature/high RH, in other words; you have to take the temperature into account too.

See this:
http://www.tis-gdv.de/tis_e/misc/klima.htm

Notice that the absolute moisture content of air is equal for say... 20C/70% and 30C/40%, whereas 70% and 40% figures are pretty far from each other. So, beware; RH figures can be deceiving when not paired with ambient temperature...

Regards,
Loris.

 

[Xandros]

Thanks for the great link ! I will now be able to consider the absolute humidity when printing !

As about the moisturizer, i'll consider it eventuallly even though it's a bit more expensive here.

 

[sdivot]

Xandros,
What is your exposure source? If your doing it in the sun, I just don't think you will get consistent results. I'm sure some will disagree, but an exposure unit would eliminate exposure variables. Have you considered putting a humidifier or a dehumidifier in your darkroom to achieve a consistent environment year round?
Steve
www,scdowellphoto.com

 

[Xandros]

Nope it's a 300W UV lamp which didn't move a millimeter between the prints I let it pre-heat to only begin exposure when it is at full power. I guess I'll have to get a humidifier / dehumidifier.

 

[sdivot]

I live in Houston, Texas. It is very humid here. I'm making prints now, and I'll be interested to know what happens when I make the same prints in the wintertime. I'll keep you updated if things change with the humidity levels.
Good luck!
Steve
www.scdowellphoto.com

 

[Katharine Thayer]

Thanks Steve, more data is always useful, although the humidity/exposure relationship is established beyond doubt, not just with my tests. In laboratory studies where the temperature was held constant and the humidity varied, the relationship is almost vertical. This is borne out by the nice chart Loris linked, put together with my experience: when I was living at the beach, the most common environmental condition (I printed in a studio with the windows wide open, winter and summer, so the outside climate was the same as the inside climate) year around was around 50-55 F and 85-90% humidity. According to this chart, that's around 10% absolute humidity. My routine exposures in those conditions were 2-3 minutes. On an unusually dry day when the humidity plunged to 17% and the temperature was in the low 70s (somewhere around 4% absolute humidity) my exposures zoomed to 20+ minutes. In other words a 6% change in absolute humidity can generate a 10x change in exposure. As generations of gum printers have demonstrated, you can print gum without a humidifier or dehumidifier, or without climate-controlled conditions, but you do need to be aware in changing conditions to vary your exposures accordingly.
Katharine

 

[Xandros]

Hmm very intreresting indeed, then we would just need to find a formula close enough to the experienced change in exposure times so we could calculate this. Because if 6% is 10 times, is 3% 5 times or is there another type of progression ?... Here from what I gathered from the weather reports archives, the humidity dropped from 12% absolute to 5% absolute, so about 7% too in fact ...

 

[Katharine Thayer]

Hmm... With gum I would never give an observation as a rule.. I was just sharing that informal observation in support of the established observation that says "less humidity = more exposure" and that the relationship is a steep one; that's absolutely as specific as I'd go. I would never say "6% is 10x" as a rule, on the basis of an informal observation. I guess my point was that if you go by the relative humidity, it seems sort of reasonable that if you go from 90% humidity to 17% humidity it's going to make a big difference in the exposure, but when you see that that's really only a 5-6% difference in absolute humidity, it brings home the fact that the relationship between humidity and exposure is indeed a strong one.

You're going to need to do step tablets to determine the exposure anyway; just rely on what the step tablet tells you and print gum, would be my advice. Keep track of your observations and over time, we add to the database of observations. If we ever eventually developed a humidity-exposure formula that proved universal, that would be great, but I'm not holding my breath since that's never happened for any other gum law that people have tried to establish (except for the most general, which is why I try to stick with general principles that I know are universal). Um (looking down) I see I'm standing on a soapbox, I'll get down now.
Katharine

 

[Jon Harwood]

Gum and Humidity

I agree about establishing rules for gum that will apply universally.

I have a "rule of thumb" I use in my setting and I am getting some nice preliminary results within a range of fluctuation of about 20%.

However when the dry winds start here and the humidity plunges from about 60% to about 15% I will not be surprised to see my "rule" overturned.

That seems to be the way with gum.

 

[Katharine Thayer]

P.S. Anyone interested in gum printing, particularly tricolor gum, should have a look at Jon's print "Santa Margarita 1" that's currently on the main page at hybridphoto. That's gum printing:

http://www.hybridphoto.com/gallery/showimage.php?i=602

 

[Loris Medici]

Thanks for sharing that. It's nice indeed. OTOH, it's more like your kind of gum printing (high-keyish w/ smooth tones and pastel colors)

 

[Katharine Thayer]

Well, of course, that's what I like landscape photos to look like, a natural expression of a natural scene, without any surreal boosting of saturation or contrast. I took up gum because I found the color in most color photography to be much too saturated for my taste, and I wanted a way to print a more subtle and personally pleasing image. It took me a while to learn how to print gum to look that way; I had to back way off on the pigments and choose less saturated colors to get it right. But yes, I think this is a beautiful gum print, and yes, it's how I like color pictures, especially of natural scenes, to look. I don't suppose that's surprising. I like to be able to look at a color picture and enjoy it and take it in instead of having my eyes assaulted by unreal color or contrast.

(I also hated Ansel Adams' work until someone pointed me to his earlier work, which is much more subtle and natural than the later high-contrast poster stuff.)

 

[Loris Medici]

...

(I also hated Ansel Adams' work until someone pointed me to his earlier work, which is much more subtle and natural than the later high-contrast poster stuff.)

It's the advance in technology & technique that ruins Adams' work for you then; the lenses got sharper and more contrasty (better production lines, multi-layer coatings etc.), films got better, also Adams' technique got sharper and stronger... It's not coincidence that people are looking for single coated lenses and/or manufacturers produce "special" single coated optics for B&W photogs. See Cosina's 40/1.4 Nokton SC for instance; you'll definitely get more shadow detail with such a lens...

Anyway, what distinguish a master from an apprentice is to force the limits with subtlety, I mean w/o the "in your face" attitude... If someone is more attracted to technique (instead of unknowingly appreciate it as a means to transfer the message/emotion) when looking to a photograph then it's probably so a) because of the viewer is a nerd b) because that's an apprentice's work or c) both... Photography (especially B&W photography) is like make-up to me; the best make-up is the one you don't notice its presence, whereas the best photographs are the one you're not attracted to the technique "in the first place". Whether too subtle or overworked...

 

[Katharine Thayer]

Loris, agree with the last bit but not the first, since I've seen several examples of the same Adams image printed(by him) early and late in his career, and the early ones are natural and subtle; the later ones printed with way too much (for my taste) contrast. So it's not the lens, it's how he chose to print the picture. But we're way off topic for alternative process (let alone gum and humidity) now; how did we get here?

 

[Jon Harwood]

Gum and Humidity

Thanks for the compliment Katharine!

P.S. Anyone interested in gum printing, particularly tricolor gum, should have a look at Jon's print "Santa Margarita 1" that's currently on the main page at hybridphoto. That's gum printing:

http://www.hybridphoto.com/gallery/showimage.php?i=602

 

[janessa]

Basically for cyanotype you need super thick paper (thick like watercolor grade) so it won't warp too much. Fine printmaking paper also is good. I have no idea about gum bichromate.

 

[Jeremy]

Basically for cyanotype you need super thick paper (thick like watercolor grade) so it won't warp too much. Fine printmaking paper also is good. I have no idea about gum bichromate.

This is a very misleading statement. I've successfully printed many cyanotypes on a 32lb rag typing paper. Cyanotype doesn't 'need' a certain thickness of paper, just one that has enough wet strength for processing. (and works well with the process).

 

[donbga]

This is a very misleading statement. I've successfully printed many cyanotypes on a 32lb rag typing paper. Cyanotype doesn't 'need' a certain thickness of paper, just one that has enough wet strength for processing. (and works well with the process).

Double ditto what Jeremy said.