Showcase for Your HCWP's

[nmp]

I watched the video

and tried this on my "second batch" (too dark).

• reduces density as advertised
• but also de-saturates the characteristic cyanotype blue
• and hydrogen peroxide does not do much

I guess I'll have to pay more attention to "details" such as hygrometry.

Does Kallitype have the same demands on hygrometry control?

Another idea - do the alkali treatment that reduces the blue but adds yellow ferric hydroxide. Then wash thoroughly to remove any ferrocyanide ions formed as a result. Then immediately treat with oxalic acid (don’t let the paper dry) which will form soluble ferric oxalate with ferric hydroxide. Wash and now you don’t have the yellow in the paper and original cyanotype blue will be back. The highlights will also go back to paper white. It is important to wash the paper before oxalic acid because in presence of ferrocyanide it will convert ferric hydroxide back to Prussian blue.

:Niranjan.

 

[Raghu Kuvempunagar]

"touchless puddle pusher"

When you get a chance, would you mind sharing a pic of this apparatus?

 

[Raghu Kuvempunagar]

Another idea - do the alkali treatment that reduces the blue but adds yellow ferric hydroxide. Then wash thoroughly to remove any ferrocyanide ions formed as a result. Then immediately treat with oxalic acid (don’t let the paper dry) which will form soluble ferric oxalate with ferric hydroxide. Wash and now you don’t have the yellow in the paper and original cyanotype blue will be back. The highlights will also go back to paper white. It is important to wash the paper before oxalic acid because in presence of ferrocyanide it will convert ferric hydroxide back to Prussian blue.

:Niranjan.

Great idea. Would Citric Acid do the same job as Oxalic Acid in your idea? Thinking about other less toxic options, would using Ascorbic Acid instead of Oxalic Acid followed by Peroxide treatment work?

 

[Patrick Robert James]

As far as the video with the bleaching back that was posted, seems it would just be easier to do it right in the first place. The print in the end looked ok though so whatever works I guess.

I've used Sodium Sulfite to bleach cyanotypes. Works great when you have overdone the exposure a little or if the coating is older so highlights aren't as clean. IIRC I've tried it on heavier prints and past a certain amount of bleaching things start to look off.

Never noticed humidity affecting cyanotype myself but I live where there is almost always humidity. I doubt there is that much difference between low and high for me.

 

[NedL]

When you get a chance, would you mind sharing a pic of this apparatus?

Raghu, mine is just a length of 1/2" PVC irrigation pipe with 1 inch wide blue painter's tape "shims" set a few inches wider than the paper. The number of wraps of painter's tape can be adjusted for different paper thicknesses and keeps the pipe maybe 1 or 2 mm above the surface of the paper. The pipe never touches the paper, and the PVC is hydrophobic and easy to clean. Easy to move the tape for wider paper or replace if it gets contaminated. I use it with the paper on a sheet of glass. I think people also use something like this for coating emulsions -- it proabably has another name!

Here is Niranjan's description. I think his version has fixed rails as the shims, but it's the same idea. Only liquid ever touches the paper.

I first tried it when I was experimenting with "developing" cyanotypes with pot ferri, but I also tried it on your ferro-blend when I had some smearing. I still got a little smearing just from the motion of the liquid moving across the paper. That was solved by dampening the paper a little before applying the "developer" and after that, a brush worked fine.

 

[bernard_L]

Another idea - do the alkali treatment that reduces the blue but adds yellow ferric hydroxide. Then wash thoroughly to remove any ferrocyanide ions formed as a result. Then immediately treat with oxalic acid (don’t let the paper dry) which will form soluble ferric oxalate with ferric hydroxide. Wash and now you don’t have the yellow in the paper and original cyanotype blue will be back. The highlights will also go back to paper white. It is important to wash the paper before oxalic acid because in presence of ferrocyanide it will convert ferric hydroxide back to Prussian blue.

:Niranjan.

Will do. Need to order oxalic acid before it is banned in EU.

Regarding cyanotype and humidity...

In my experience cyanotype is probably the process that is least sensitive to humidity. I have made successful cyanotypes with the ambient relative humidity ranging from 32% to 80%. I don't know if these are the limits as my records don't show values outside of this range.

Possibly how crucial is humidity control depends on the adopted procedure. I had produced inkjet negatives using EDN (Easy Digital Negative) and was really pleased to see that, as expected, exposing to UV for the same time as the EDN calibration chart resulted in "perfect" cyanotypes. So far I had been drying the sheets (after coating) with a hair dryer. The next day I made duplicate prints, but air-dried instead.
In other words, possibly the various statements about humidity control are all true, but strict control is needed if one relies on a calibrated exposure --instead of test strip just before the print. Just a guess.