[Alt-photo] Re: Sulfamic Acid for Paper Acidification

[Loris Medici]

Hi Serdar,

The evaluation depends on the process too; for instance, pt/pd is more
forgiving about the acit pre-treatment operation but new cyanotype and
argyrotype aren't. A paper treated in HCl would work OK with pt/pd but not
OK witj new cyanotype or argyrotype. I'm personally more interested in the
latter right now, I wasn't printing argyrotype much because it was more
demanding (than vandyke) about paper, now that I make it work with many
papers, I'm about to dump vandyke forever in favour of  argyrotype...
Sulfamic acid pre-treatment made quite difference for me, because when it
works (or you make it work with sulfamic acid), I find argyrotype being a
lot better than vandyke in every aspect. (Dmax, tonal range and smoothness,
hue...)

Regards,
Loris.


2013/5/5 Serdar Bilici <sbilici at gmail.com>
>
> Hi Loris,
>
> I agree that there might be a sweet spot for dmax with HCl, but really
why fiddle :)  Sulfamic acid has a great advantage at storage, it is not as
corrosive as HCl to metals, so it is safer to work indoors, the prints have
better dmax in comparison.
>
> (You already know this bit, but I should include it for other readers)
> When I made a research about sulfamic acid and its uses, I have found out
that sulfamic acid is used in modern descaling systems to remove calcium
deposits instead of HCl. Due it is less corrosive but it has equally strong
acidic nature. As you said, probably sulfamic acid leaves the paper in
better condition compared to HCl due to its less corrosive nature.
>
> In terms of dmax, HCl treatment gave me the poorest results among the
acids I have tested. Although, it was the right choice theoratically,
(being a mono-acid, highly water soluble byproduct, fast reaction, good
capacity) practically the results were not so appealing. Considering that
the fumes of HCl would corrode the metals in the room it is used in time, I
understand why it is not the most popular choice to acidfy papers. Proper
ventilation is quite important when working with HCl (Dangerous chlorine
gas release), on the other hand Sulfamic Acid + Calcium carbonate reaction
produces only CO2 gas.
>
> Compared to HCl it is a WIN-WIN.
>
> Regards,
> Serdar