oxalic acid presoak

[philsweeney]

Using a 2% oxalic acid presoak on arches watercolor hot press for kallitype I was able to get good and sharp results. Without the presoak the paper just did not do well. Though the presoak helped, the print is a little blotchy. The blothchyness may be due to the pot. dichromate. I soaked the paper for 2 minutes. Could I have soaked the paper too long, where the oxalic acid affects the sizing and causes the blotchyness? Curious how long others presoak when they do so? And could the presoak be effective with a 1% solution vs the 2%.

 

[nze]

Hello Phil

% of acid bath depend on the paper and the process. Some paper just need to be brush with a 1% acid oxalic solution and other may need an 5% bath for 5 minutes. This is link to he buffer in the paper.

On some paper this bath could play on the sizing . But this depend on the quality of the paper. I don't think it will happen on arches watercolor hot press which have a quite heavy gelatin sizing.


Another thing I think about is that normally you got to use a free acid oxalic ferric oxalte solution , for you kallitype . If you did so, the acid you put inyour paper perhaps act with your sensitizer. I am not a kallitype user so I am not sure of the effect of some acid oxalic in the sensitizer.

 

[wm blunt]

I have found with some papers, such as Platine, that I get better results when I brush on the oxalic acid instead of doing a dip and dunk. I figure the soak is affecting the sizing in the paper. I place a sheet of paper on a piece of plexiglass and hold it at a glare angle to see that I am covering the printing area when I brush the acid on. I use a 2% solution but a 1% may be fine, never tested that. I spend a whole evening precoating sheets and the next day I'm ready. I guess you could coat one sheet at a time and force dry but I haven't tried that. I use for Platinum/Palladium printing so that may make a difference. Hope this helps. Good luck

 

[PJC]

I've had mixed results with Arches paper. I too would get some blotches and believe it's caused by the sizing. The blotches would occur after long wet times and would be present regardless if an acid presoak was done or not. I think some batches of Arches are not evenly/consistently sized and the blotches result. I've never had this problem with Arches Platine, but it would frequently happen with Aquarelle hot press.

Regards, Pete

 

[philsweeney]

PJC: I should have said the highlights and midtones were mottled versus individual blotches. I tried to use the paper again with a shorter oxalic acid bath and the results were poor. I was able to get reasonable results on this paper with brown print sensitizer (double coating). Wondering whether anyone has tried to acidify paper with other acids like citric acid?

 

[PJC]

Phil, when I tried Aquarelle, I tried both an oxcalic acid and citric acid bath and got the same result. The blotches I got were most noticable in the highlights and mid tones, but were present throughout. The blotches were definitely caused by the Aquarelle paper as a different batch of paper processed in the same chemistry at the same time came out just fine. I'm convinced it's the sizing.

Regards, Pete