Hand coating...humidity?

MurrayMinchin

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Hi there,

I’m about two days away from making my first salt prints and have a few questions about humidity.

I bought a small digital device to keep an eye on humidity in the darkroom and so far it has gone from 57% during rainy fall weather to 27% during a winter dry spell. Is this a normal fluctuation?

What would be considered the ideal relative humidity when hand coating paper prior to exposing it...or...is it easier to maintain the relative humidity somewhere in the middle at as constant a level as possible?

Thanks in advance.
 

revdoc

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I don't know much about salt printing, but for vandykes I use a similar device (two bucks on eBay), and it fluctuates in a similar manner. The actual numbers will depend on your climate, central heating, AC, etc.

My usual approach is to adjust drying time to the current humidity. I always start with the same volume of solution per unit area, and dry with a small fan for the RH divided by 6, in minutes. E.g., 10 minutes at 60%. What matters with VDB is the humidity at the time of exposure, and the method I use is good enough for me. The exact numbers will be different for you, hut I don't see why the overall approach won't work in your case.
 
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MurrayMinchin

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Sneaky.

So with today's relative humidity of 27% you would dry for 4.5 minutes?

Sounds imminently plausible and much cheaper than stabilizing humidity in the room. Thanks.

Darkroom is in a basement with an electric baseboard heater.
 

Herzeleid

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Hi there
Fluctuation of humidity in seasons is normal. My hygrometer shows similar fluctuations after rain.

Well I have never considered relative humidity for paper drying times. I think given enough time moisture in the paper eventually will come to an equilibrium with the environment so longer duration would not change the final moisture in paper. I usually have to work with RH lower than %20, and I always dry my papers 30 mins.
However, high RH effects absorbance of the paper, in some processes the exposure time and the DMax of the print. I always brush coat my salt prints and I add a drop of glycerin per ml of the silver I use. Glycerin acts as a weak emulsifier (I also add citric acid and food dye) but most importantly it acts as humectant. I can't give scientific values but the prints with glycerin always print better DMax.
Most of the iron processes VDB, argyotype, pt/pd,kalitype benefit from the addition of glycerin except cyanotypes.

Dramatic fluctuations in humidity effect paper dimensions and it causes lot of problems when printing gum or similar multi layer processes.
 

fgorga

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Seasonal variations in humidity are the norm most places in the world. My unfinished basement dim room varies from as low as 35% (with the wood stove running this time of year) to as high as 85% (in the worst days of summer) here in New Hampshire. Typically the humidity is in the range of 50-70%.

For salted-paper printing, my practice is, I think, a bit different than most in that I do not coat sheets of paper one-at-a-time. Rather, I estimate the number of prints that I am going to make in a session and coat that amount of paper at the beginning of my session and let the paper dry for an hour before starting the first print. (I will even coat the evening before on occasion if I need to get started early the next day.) I also salt paper in largish batches by soaking it in the solution and letting it dry for 12-24 hours before storing it in ziplock bags.

My practice for cyanotype is the same as for salted paper... sensitize is batches and dry for an hour before beginning the first exposure.
 

Ian Leake

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I make platinum prints rather than salt prints, so there may be some nuances that I'm not aware of. Having said that, I've found that paper humidity is far more important than atmospheric humidity, because this affects how fast the sensitiser is absorbed, which in turn affects drying time, Dmax, image quality, etc. I've found that paper stored in 60-65% RH performs best, at least for platinum. But I wouldn't worry too much about this when you're starting out unless your paper is very dry.

You can easily increase paper humidity by suspending it over water for a few minutes. I use a darkroom tray containing about a cm of water, attach the paper to a steel sheet using magnets, and then lay the steel sheet over tray so that the paper rests above the water (without it touching the water!). You can improve on this design by using a cat litter tray or other fully sealed configuration, and using a bath of a saturated salt solution rather than plain water.

Some people steam the paper using a kettle or humidifier, but with larger sheets this is too inconsistent for my preferences.
 
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MurrayMinchin

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Thanks all for your pearls of wisdom.

It's been snowing for the last couple days so has bounced from a low of 19% RH during a -19C (-2F) cold snap last week to 35% today. This should be a good RH to start, being about 1/2 way between the extremes measured so far.

Unless something comes up to drag me out of the darkroom, today should be the day to stop preparing and actually get started down this new path!
 
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MurrayMinchin

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Ian Leake said:
Happy Printing!
Click to expand...

I haven't felt like this since I mixed up my first batch of print developer and put my first negative into an enlarger
 

removedacct1

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MurrayMinchin said:
I haven't felt like this since I mixed up my first batch of print developer and put my first negative into an enlarger
Click to expand...

Are you salting your paper using a gelatin + ammonium chloride recipe? I’ve found this to be far better than salting paper without a sizing.
 
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MurrayMinchin

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paulbarden said:
Are you salting your paper using a gelatin + ammonium chloride recipe? I’ve found this to be far better than salting paper without a sizing.
Click to expand...

Starting with ammonium chloride (no gelatin) on Hahnemühle Platinum Rag, but may try using gelatin or arrowroot in the future.

Will get started after my morning run.
 

fgorga

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Have fun!

I made my first salted-paper prints last February and have been having great fun with it.

But watch out... it is addictive. Hopefully you won't fall into the trap that I have. I made my first Pt/Pd prints about two weeks ago.

Looking forward to seeing some of your prints in due time.
 

removedacct1

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MurrayMinchin said:
Starting with ammonium chloride (no gelatin) on Hahnemühle Platinum Rag, but may try using gelatin or arrowroot in the future.

Will get started after my morning run.
Click to expand...

HPR is good. I think you'll find you get a much better print when using a sizing binder, but by all means, get started!
Are you making a digital negative or using a standard negative (film and chemical derivation)? Have you read Ellie Young's document on the subject? There's a lot you can learn from it, with especially useful information on the subject of making the ideal negative for salt printing (Use FP4 processed in double strength PMK)
 

Alan9940

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Since I live in the desert, the humidity level in my papers is always a concern. I print pt/pd and for many years used a hydration chamber that I constructed out of a plastic storage container, a tear drop humidifier, and shelf fabricated out of plastic plumbing pipe and nylon fishing line. It worked, but control of the humidity level was difficult, if not impossible. A year or so ago, I picked up the book "Platinotype" by Pradip Malde and Mike Ware and built the hydration chamber as outlined therein. The humidity level obtained is very consistent and can be modified to various overall levels by the type of salt used. I used regular table salt and the chamber runs at a consistent 76%. Highly recommended, if a constant humidity level is important to you.
 
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MurrayMinchin

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paulbarden said:
...Are you making a digital negative or using a standard negative (film and chemical derivation)? Have you read Ellie Young's document on the subject?...
Click to expand...

Digital enlarged negatives from digital files to start, then from scans of 4x5 negatives later.

Have Ellie Young's book, The Salt Print Manual.
 
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MurrayMinchin

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Thanks...will check it out.
 
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MurrayMinchin

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NedL said:
I hope you enjoy making salt prints today!
Click to expand...

Darn...something did come up. Hope to at least get the first coat on some paper tonight and hit the ground running tomorrow!
 
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MurrayMinchin

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How does that saying go again, "To be master at anything, you need to make 10,000 mistakes"

One sad, weak attempt at a max black test print done, but at least I achieved density! Only 9,999 more mistakes to go...


Thanks. Not sure if I'll be needing one, but put a Vimeo link below of Malde putting together a hydration chamber for future reference (click on "watch video" and it'll take you there)

 
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MurrayMinchin

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I played with your idea. RH was 35% today and I tried double coating a piece of paper in my quest for a good solid max black test. Turns out with my fan and distance to the paper, it was RH divided by 5 for a 7 minute drying time. This worked for both double coating and before exposing the paper.

Will be interesting to see if this holds up as RH goes up & down.

Thanks!
 
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