Relative Humidity and New Cyanotype

[4LivingWage]

I believe diluting the solution will be the answer to my problems. I printed two images, both well overexposed, which I believe is good news. The new Cyanotype is supposed to have a shorter exposure time. I hope to dial this in in the next couple of days. You all have been a great help.

 

[koraks]

Great, that's promising news; I really hope you can get this to work!

 

[cirwin2010]

Per Christina Anderson's notes, she dilutes the new Cyanotype formula 1:1 with water. She states it aids in eliminating coating issues, but there may be a slight loss in dmax.

As mentioned by other posters, you can mix NC and CC 1:1. Other than aesthetic considerations, I believe the benefits of doing such is similar to diluting NC with water but without actually diluting the potency of your sensitizer. I tried this once to see if it would help me coat HPR, but no success there.

Christina Anderson's book and paper chart are excellent resources. However, do not take her results as gospel. I have found through my own testing that I get different results than she does and I would encourage everyone to do their own testing.


Just to name a few things that don't match her results or that I don't agree with:

1. My paper results of what I've tried haven't lined up with her results, especially regarding HPR and New Cyanotype. I also don't know how thorough some of her paper testing is as she will sometimes state things like "may be improved with addition of citric acid." Suggests she may not have tested it, which is fair considering how many papers she as tried.

2. While I am using a different UV source (12x 395nm Barrina LED strips about 8" from paper), my exposure times are very different than her results in time (shorter) and the relative differences in time between CC and NC from one paper to another don't match up. Different wavelength perhaps affecting results compared to UV black light bulbs?

3. I disagree with her results on using 10% FAC vs 20% FAC regarding exposure time with Classic Cyanotype. She states she gets shorter exposure times with 10% despite conventional wisdom stating that 20% will have shorter exposure times. I get notably shorter exposure times with 20% FAC using Classic Cyanotype. Again, could be a UV source difference?

4. I think double coating Classic Cyanotype is worthwhile if you want more dmax and less grain. Results may be paper dependent.

5. Tween20 can be detrimental to results if it causes your solution to penetrate too deep into the paper. You can loose dmax and light can penetrate and expose solution deeper in the paper causing a sort of edge bleed effect. Humidification of paper has given me better results than tween20 in my experience.

6. I don't get the 2-3 stop exposure speed improvement with New Cyanotype vs Classic Cyanotype. For example using acidified Canson XL Watercolor, my exposure time for classic is 6m and 4m for new cyanotype. Through my testing I have found that new cyanotype either requires similar exposure time to classic, or just slightly less. This could be due to the light source/wavelength I'm using as I think Mike Ware and Christina Anderson are using 365nm lights. It could also be how I am determining exposure time. I find that New Cyanotype tends to form a bit of a shoulder when reaching max dmax. It may get almost to maximum density with a given exposure, but I can get slightly more dmax with disproportionally more exposure. Excess density in midtones and highlights then get calibrated out in my ink profiles.

 

[4LivingWage]

I'm still trying to dial in exposure. I also slightly re-engineered my curve, printed a photo for 7 mins, and it is close; likely will need 7'30" for optimal exposure. This compared to 12'30" before dilution. I'm not a chemist, didn't even take chemistry in school, but that sounds a bit counterintuitive. I have put a scant drop of tween20 in my 30 drops of sensitizer and am using Arches Aquarelle. So far, no issue coating, no brush marks, and no graininess, as well as no crystallization. I'm thrilled! I'll print another and post the results later.

 

[koraks]

For example using acidified Canson XL Watercolor, my exposure time for classic is 6m and 4m for new cyanotype. Through my testing I have found that new cyanotype either requires similar exposure time to classic, or just slightly less. This could be due to the light source/wavelength I'm using as I think Mike Ware and Christina Anderson are using 365nm lights. It could also be how I am determining exposure time. I find that New Cyanotype tends to form a bit of a shoulder when reaching max dmax.

Virtually all processes have a shoulder.
Here's the curves the last time I plotted classic vs. new cyanotype:

That was after fixing my issues with New Cyanotype as reported on here: https://www.photrio.com/forum/threa...hort-curve-high-contrast.206252/#post-2788805
Note how esp. the toe is much different while the shoulder behavior is quite similar.
The fact that your exposure times are so close suggests something odd is going on, likely with your New Cyanotype process. Note that in the thread I linked above I got similar results to yours before I tracked down the problem with the first wash; after that, everything snapped back into consistency.

I don't think the wavelength of your light source explains the differences you're observing between your practice and the data points in Anderson's and Ware's works.

 

[cirwin2010]

Virtually all processes have a shoulder.
Here's the curves the last time I plotted classic vs. new cyanotype:

That was after fixing my issues with New Cyanotype as reported on here: https://www.photrio.com/forum/threa...hort-curve-high-contrast.206252/#post-2788805
Note how esp. the toe is much different while the shoulder behavior is quite similar.
The fact that your exposure times are so close suggests something odd is going on, likely with your New Cyanotype process. Note that in the thread I linked above I got similar results to yours before I tracked down the problem with the first wash; after that, everything snapped back into consistency.

I don't think the wavelength of your light source explains the differences you're observing between your practice and the data points in Anderson's and Ware's works.

In the example I mentioned, I am using sulfamic acid for the first wash. Specifically 1% sulfamic acid for NC and 0.2% sulfamic acid for CC. I'm not keen on trying HCI for safety reasons (or other mineral acids). From my own testing and Christina Anderson's data, the type of acid used during the first wash can and will affect the contrast curve and exposure time required for achieving the highest dmax.

This could be another variable affecting my results regarding exposure time.

I could also be overexposing a little more than needed and my ink profiles are canceling that out. Easier to error on slight over exposure with my process. But I don't think I am adding more than a minute extra if at all.

The length of exposure doesn't bother me much. Between acidifying the paper, prehumidying NC or double coating CC, the process to make a print is so long I don't care about a difference of a few minutes.

 

[4LivingWage]

I believe I have been able to surmount the obvious problems new cyanotype has been dealing me with a simple 20% dilution of the solution. Now, I would love to hear how I can improve it. Do you see some evidence of fogging in the image?

 

[koraks]

That's very hard to tell since there are no masked areas on the print. But overall that print looks fine to me!