Mottling on Arches WC Paper

What do you suppose is the cause of the mottling apparent on this print?



It's a Van Dyke printed on 140 Lb HP Arches paper. I normally print on FA and Lanaquerrelle with good results but I ran out and printed the above on Arches.

Thanks,

Thomas

Tom Taylor said:

What do you suppose is the cause of the mottling apparent on this print?

It's a Van Dyke printed on 140 Lb HP Arches paper. I normally print on FA and Lanaquerrelle with good results but I ran out and printed the above on Arches.

Thanks,

Thomas

Click to expand...

This has very occasionally happened to me before with Cyanotypes and Arches HP 140 paper, usually when the print was left face up, very damp on a surface or tray. Although I don't know the exact reason, I concluded it was due to washing as I often make test prints where I cut a large sheet into smaller pieces and the occasions it happened, the other pieces of the sheet were fine, and it affected the part of the paper where there was no sensitiser too.

I always just use tap water, and suspect it is a result of the chlorine (which can vary in level slightly) reacting with the buffer/chemicals in the paper. Although manufactures say 100% acid free, unbuffered, free from chemicals etc etc etc almost all modern papers in reality have something in there. You can usually see this by wetting watercolour paper for a long time then shining a bright light through it - you will the stuff they have added show up as white splodges in the paper which won't be visible if you again shine a bright light thought it when completely dry.

Too much tween-20 (if you use it) in the sensitiser solution can create a similar effect though it looks much more pronounced than your example.

These types of problems caused me to give up on VDB prints. I started with Arches watercolor paper, then tried papers for Pt printing with similar results. Reading the above reply, perhaps it was my water. Makes me want to try again.

I think something's terribly wrong with that paper (sizing?)...

Vandyke's not that much picky with paper but being an iron-silver process, it requires a neutral or acidic surface for best results - you can't get the best out of it with buffered papers. (Which Arches paper is that? Arches has many different papers...)

Can you please describe your (whole) procedure (and formulae) in a very detailed manner?

Thanks for the replies everyone

The paper is Arches WC color paper which I get from a local Art Blick store: http://www.dickblick.com/products/arches-watercolor-paper/

The paper is well senstized and allowed to "set" for a few minutes before using a hair dryer set on the low cool setting on the back side until the paper is "bone dry." Tween is not used. The first 5 minute wash is in distilled water with a pinch of citric acid. The second wash (2 minute) is in tap water with a pinch of cirtic, and the 3d, also 2 minutes, is in running tap water. The local municipal water source is snow melt from Hetch Hetchy (Yosemite NP) and using distilled water is probably not needed in my case but I use it for the 1st wash anyway. After washing the paper is hung to dry in a dark closet.

James says that Arches is "fair" for VD. I wonder if the mottling is a result of the citric acid?

Thomas

Ok thanks for the detailed description. Can you please try once more w/o blow drying the paper? Just coat the paper, let the sensitizer set until the surface becomes matte - takes 5-10 minutes (15 max!) depending on the humidity of your studio - and then hang the paper and wait further to complete 45 minutes total drying time and expose that way. From your description, it looks like the mottling was caused by (force) drying the paper blowing from the back, resulting a paper with uneven moisture content. *Let the paper dry in peace!* (Edit: Or, if you feel like you absolutely have to use the hair dryer, then blow both the back and coated sides of the paper.)

BTW, I personally don't prefer exposing bone dry paper with Vandyke; you get a much better dmax (and speed) with some humidity in the paper...

Let us know how it goes and good luck!

Regards,
Loris.

If you soak an unused sheet of paper in a tray of water for 10 minutes or so, and see the same blotchiness when you hold it up to the light, its the sizing. Otherwise I have no idea at all.

I had this problem a while ago and yes, just soaking the paper gives the same result. I ended up buying different paper.