trouble with rod coating

Json · Sep 3, 2017

Hi all, I was hoping to get some advice on rod coating onto paper.

I've just got myself a nice looking glass rod from wetplatesupplies that has bent upturned handles on either end and have been practicing with cyanotype. Unfortunately it was not as easy as I imagined!

Basically, the solution is being left in streaks rather that a solid coating as I draw it down the paper. The only way I'm able to get a complete coat is by alternating vertical and horizontal strokes or shifting the rod around. Does anyone have any idea why this might be happening? is this normal on the first few up and down motions?

I don't think the streaking is consistently in the same area and to my eyes the rod and the table I'm working on are both flat and straight.

Any help is appreciated

Alan9940 · Sep 3, 2017

Don't know about cyanotype because I've never done it, but I had the same issues with rod coating for pt/pd. I always contributed the streaking to the paper; that is, as the paper moistens it "buckles" causing it to be relatively not flat. I've read that some printers put several sheets of newspaper under the paper to be coated to provide some "give" to the surface. Bottom line for me is that I've tried rod coating several times and finally gave up in favor of brush coating. Never had any issues with a brush.

Photo Engineer · Sep 3, 2017

The surface of the paper may be repelling the coating medium, or soaking it up too fast. I cant tell without seeing it. If it is the former, use of a surfactant such as Photo Flo might help. You would only need about 1 drop in 100 ml of coating solution.

PE

ced · Sep 3, 2017

Perhaps you are not putting enough chemical under the rod and the workplace must be level, also maybe do a degreasing of the rod...

Json · Sep 3, 2017

Thanks for the helpful suggestions guys.
I will try out degreasing the rod first since it seems like an easy thing to rule out (plus I have been handling it quite carelessly). And I'll definitely have some surfactant on hand next time too.

Hopefully I can figure this out because I much prefer the idea of rod coating...

dwross · Sep 3, 2017

Following up on ced's suggestion, you might try raising the glass rod with a few wraps of tape at both ends. It sounds like the rod is scraping the paper (especially a problem if the paper is CP or otherwise textured).

Json · Sep 3, 2017

Thats an interesting idea dwross - I'll definitely keep that in mind next time too. The streaked areas without solution looked bone dry so I'm not sure if the rod is scraping the paper or something else is going on but I have lots to think about now

jeffreyg · Sep 3, 2017

I don't do cyanotype but I do platinum/ palladium and have used both a glass rod and brush. I find it best to slightly moisten the paper before coating. For the rod I mix the sensieizer and draw it up into a small syringe a d slowly express it against the syringe, lift the syringe slightly and then put it back against the paper having made sure there are no voids and then coat.

http://www.jeffreyglasser.com/

pschwart · Sep 3, 2017

- what size rod?
- what is the image size?
- how much solution are you using?
- what paper are you using?

Json said:
Hi all, I was hoping to get some advice on rod coating onto paper.

I've just got myself a nice looking glass rod from wetplatesupplies that has bent upturned handles on either end and have been practicing with cyanotype. Unfortunately it was not as easy as I imagined!

Basically, the solution is being left in streaks rather that a solid coating as I draw it down the paper. The only way I'm able to get a complete coat is by alternating vertical and horizontal strokes or shifting the rod around. Does anyone have any idea why this might be happening? is this normal on the first few up and down motions?

I don't think the streaking is consistently in the same area and to my eyes the rod and the table I'm working on are both flat and straight.

Any help is appreciated

Vaughn · Sep 4, 2017

I rod coat pt/pd up to 8x10.

Some papers' sizing does not allow the solutions to enter evenly. I work like Jeffery, using the syringe, and lifting the rod slightly and wiggling it to distribute the solution along the whole rod. Sometimes it takes two or three passes to get all the area wet -- at which time I switch to a brush and lightly move the solutuion around.

I have a board wrapped with a layer of felt that I coat on -- I like the slight give under the paper as I pull the rod across.

Json · Sep 4, 2017

pschwart said:
- what size rod?
- what is the image size?
- how much solution are you using?
- what paper are you using?

rod size: 7.5"
image: 7.5x6"
solution: 1.7ml
paper: Hanemuelle platinum rag

I think I'm using enough solution because after managing to coat it completely (after doing horizontal and vertical coatings) there was a puddle left over to blot

Dan Dozer · Sep 4, 2017

I've found that coating with Pt/Pd is much easier than with Cyanotype regarding getting fully even coverage. Pt/Pd is a thicker solution and flows on more evenly, especially with the glass rod. However, your "problem" might not be with your technique, it might be with using the rod itself. With the thinner/watery solution that Cyanotype has, getting the right pressure and amount of solution between the paper and rod is more critical. If your paper is softer, it may be soaking up the solution very quickly and only the area with the most amount of solution gets the good coverage. Those areas with less solution might be soaking in too fast for the rod to effectively coat. Another thing you may look at is that when the glass rod was heated up to bend the ends, it might have bowed out a little in the wrong direction when the bends were done. Take a very close look a the rod from end to end to see/ensure that it is perfectly flat/straight and that neither end has any bows in it. I use the push rod from Bostic and Sullivan have never had any problems coating Pt/Pd with it at all. However, because the Cyanotype solutions is thinner, I've always just brushed it on.

trouble with rod coating

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