Storing gum dichromate and cyanotype paper

[Mainecoonmaniac]

I'm going to start working with cyanotype and gum dichromate printing. I'm wondering if I could store paper coated with these emulsions for over a month? Thanks in advances!

 

[smieglitz]

You can't store coated gum dichromate paper more than a couple hours at best. There is something called the "dark effect" that spontaneously hardens the gum even without exposure. You really should use the coated gum paper within a few minutes of coating and drying it.

Cyanotype is also best if used promptly though it can be stored for an extended time when coated. I imagine you could get away with a couple months though there would be some change from day one, mainly in terms of bleeding and speed I think. There is/was a company called Blueprintables that sold precoated cyanotype paper and fabric. I assume most of it was coated long before purchase and it worked fine.

Personally, I'd only coat enough paper for the day/session.

 

[Loris Medici]

Cyanotype paper will keep well if the paper is chemically compatible (= no chemical fogging) and if you store it in a light tight and "absolutely desert dry" container. (With some desiccant? perhaps...) Gum dichromate will exhibit "dark effect" very quickly in humid and hot environment, much slower in the opposite, but certain. It doesn't have the same storage performance as cyanotype and even in the best / ideal conditions, it won't keep more than a day or a couple... (Something like hour/hours as Joseph says - in high humidity / hot temperature...)

 

[Mainecoonmaniac]

Thanks for the advice! Looks like I will coat what I need for the session. My other question about gum and cyanotype printing is if there's a difference in sharpness
between digital negs made on an inkjet printer vs an analog enlarged neg? I'm just trying to be pragmatic.

 

[Loris Medici]

Digital negative's resolution will be between 7 and 14 lines per mm (closer to the former) whereas you can get much more resolution with in-camera negatives. Can't speak for gum dichromate (since things change consireably when doing multiple layer prints), but cyanotype resolution is definitely much higher than 7 lines per mm. Therefore you'll definitely be able to tell two cyanotypes apart - where one is made with a digital negative and the other with an in-camera negative... Said that, you can do pretty good job with digital negatives; it's not sharpness (and such) that makes us print cyanotypes et. al.

 

[banana_legs]

I printed some digital negatives on a 600dpi printer; with cyanotype on a smooth paper and a loupe, I can see every dot defined clearly! The laser negatives only become really usable if I put 2 layers of OHP film between the negative and the paper so that the extra space blurs the dots just enough to make the tones look smooth. You also lose some of the very fine details though.

A sharp film negative can look really spectacular. For the best 'sharpness', I develop in pH 7 water rather than acidified developing as I find the combination of acid development and my particular papers leads to a softer image. Not developing in acidified water does mean a longer exposure is needed though, and you get a higher contrast (which also helps to enhance the 'sharpness' appearance).

Best regards,

Evan

 

[Mainecoonmaniac]

Hi Evan,

Thanks for the great tips Evan. I thought cyantype can't resolve a high enough resolution to hide the dots of the ink jet film. Now I know better. I'll try the acidified water trick.

Best,
Don

 

[Loris Medici]

I could see dots in imagesetter negatives with 2400dpi hardware / 150lpi screen resolution (using a loupe - of course!)... It's no joke; cyanotype is a damn sharp alt-process!

 

[Mainecoonmaniac]

Now it makes sense

I could see dots in imagesetter negatives with 2400dpi hardware / 150lpi screen resolution (using a loupe - of course!)... It's no joke; cyanotype is a damn sharp alt-process!

Come to think of it, it has to be sharp if it's used for blueprints.

 

[2F/2F]

Thanks for the advice! Looks like I will coat what I need for the session. My other question about gum and cyanotype printing is if there's a difference in sharpness
between digital negs made on an inkjet printer vs an analog enlarged neg? I'm just trying to be pragmatic.

Great question for Hybrid Photo dot org!