[cyanotype] - About PVA size and cyanotype

[Tetium]

Hi everyone !

I have some questions/thoughts about PVA (PolyVinyl Acetate) ([Gamblin PVA Size]) in this case.

1. Do you think sizing a buffered paper as Fabriano Artistico would prevent the fading/damaging effects caused by calcium carbonate buffer during time?

I am wondering if a layer of PVA size on paper before applying the emulsion will protect the cyanotype as the addition of fumed alumina does.
(Chemical engineer needed!)

2. I am currently trying to size my paper with PVA with different dilution ratios (1:1 — 1:2 — 1:4).​

What I currently can see is a really nice glossy effect with cyanotype (as the print is wet).

• PVA 1:1 gives a very glossy surface, with a strong shining effect.
• PVA 1:2 gives a less glossy surface, a little less brilliant than the glossy plaster effect.
• PVA 1:4 is barely visible but have some effect on visibility, a very (very) little shine.

But with PVA size I encounter a strange reaction:
The length of UV exposure is drastically affected (in my case with Fabriano Artistico) when sized with PVA.
The exposure time tends to be very reduced, by twice the time in my setup…

Is someone known if PVA has some photo reduction effects with cyanotype process?

Just some thoughts, maybe someone could enlighten me a little.
Thanks in advance!

 

[Herzeleid]

I have used PVA as sizing for gum bichromate prints. I usually printed cyanotype on buffered papers then coated with PVA before gum bichromate process.
However, a few times I had to print cyanotype on PVA sized paper then apply gum layer over it. My observation was that PVA created a barrier and cyanotype emulsion was not absorbed completely.
It was easy to remove some of the blue areas with finger rubbing.

I will guess that it is similar in your case. Cyanotype emulsion (which is acidic by nature) was not absorbed into the paper fiber and therefore it did not react with the calcium carbonate.
What you have experienced is probably how your emulsion behaves when it is applied to a buffer free paper, I do not think it is PVA specific.

I use improved traditional cyanotype formula (oxalic acid and some dichromate in it like B&S formula). I have almost 2/3 stop printing time difference between buffered and unbuffered papers.
12min with buffered, 7,5 with unbuffered papers

Regards