Mottling with Digital Negatives

[Jeremy]

I'm getting mottling in some of my prints and I think its from an interaction between the Pictorico OHP and the glass on my NuArc--like Newton Rings.

Has anyone else ever had this problem?

 

[Jeremy]

Oh, and suggestions to fix it?

 

[donbga]

Jeremy,

A few quick thoughts:

Reduce the vacuum level.

Make sure your ink is good and dry.

Place something stiff underneath the paper like a piece of matte board.

My 2 cents,

Don

 

[clay]

I was about to be a smart ass and recommend sanding the back of the negative. But really, I agree with Don: reduce the pressure. I run mine typically at 8-10 (not sure what units they use)

Oh, and suggestions to fix it?

 

[Jeremy]

I've been printing at 5psi, but will up ito 8-10 tomorrow and see if that helps.

The negatives had been printing 1-2 hours beforehand and I use a black piece of matte board underneath the paper.

I'll reprint the same negatives tomorrow without changing anything first and we'll see if it happens again.

 

[wiz]

The negatives had been printing 1-2 hours beforehand and I use a black piece of matte board underneath the paper.

One or two hours isn't enough, no matter what you do to the negative.

It's quite common for Epson negatives on OHP or HGWF to not dry completely (i.e. loose the "milky" appearance) even with days of open air drying at room temperature. A print dryer with good air circulation at 130 deg F will do the job. An easier way is to place the print's emulsion side against a piece of clean white paper, that will act as an absorber for the glycols and other nasties that give you the long drying times, and the negative will dry in less than a day.

Sandwich print and paper with some pressure. You can make a stack, alternating prints and paper, then place a large book on a stack of small negatives, or a rectangle of plywood and some bricks over a large stack.

 

[BillSchwab]

I'm getting mottling in some of my prints and I think its from an interaction between the Pictorico OHP and the glass on my NuArc--like Newton Rings.

Jeremy,

Is it possibly a ph issue with your developer? I've noticed now that I am using Platine that it seems less forgiving in this area. I was getting what I would describe as mottled prints, but upon mixing a new batch of Pot Ox, all problems ceased. I have now noticed this as several batches of developer have aged. I never experienced this with the other papers I have used.

Just a thought,

Bill

 

[clay]

You've noticed this too? Platine does seem to like fresh developer. Just another reason to mix it yourself CHEAP!

Jeremy,

Is it possibly a ph issue with your developer? I've noticed now that I am using Platine that it seems less forgiving in this area. I was getting what I would describe as mottled prints, but upon mixing a new batch of Pot Ox, all problems ceased. I have now noticed this as several batches of developer have aged. I never experienced this with the other papers I have used.

Just a thought,

Bill

 

[BillSchwab]

You've noticed this too? Platine does seem to like fresh developer. Just another reason to mix it yourself CHEAP!

I am with you Clay...

Happy to find you have had the same experience. I wish I would have figured it out a lot of wasted prints ago!

Bill

 

[Kerik]

Weird - I've had plenty of Platine problems before, but not this one. Although the stuff I have now is several years old as I haven't bought any recently.

 

[dwross2]

I am with you Clay...

Happy to find you have had the same experience. I wish I would have figured it out a lot of wasted prints ago!

Bill

Hi All:

Can you think of a way to make your experiences with Platine easily accessible to other readers (including future readers) of hybrid? That kind of information is invaluable and shouldn't be isolated to this one thread at this one time. (my opinion, of course)

re: drying digital negative: I fight humidity year-round and have found that small food dehydrators with pull-out trays and a thermostat are space-efficient and affordable. I tape a piece of greenhouse fabric like Reemay over the air intake and that really cuts down on the dust.

 

[BillSchwab]

Can you think of a way to make your experiences with Platine easily accessible to other readers (including future readers) of hybrid?

It is probably going to be pretty hard unless some sort of database is set up where each paper, process, etc. can be archived and easily searched.

Bill

 

[Jeremy]

I'm using Fabriano Artistico and haven't been able to get back to my studio yet to print again, but will make some new PotOx when I do!

 

[BillSchwab]

Weird - I've had plenty of Platine problems before, but not this one. Although the stuff I have now is several years old as I haven't bought any recently.

I've been going through a lot of it lately and this is the second batch I have noticed this with. All have been purchased within the last 2 months though and are most likely from the same run.

Bill

 

[Kerik]

Jeremy - If you're using FAEW, I don't think your issue is developer freshness. I've used developer dark enough that you can't see the bottom of the tray and never any hint of mottling. Can you post a scan of you issue so we can get a better idea what it looks like?

 

[rogein]

Jeremy,

Just for clarification - you're seeing this with 'premium' OHP cut from rolls vs the 'sheets'?

I'm getting mottling in some of my prints and I think its from an interaction between the Pictorico OHP and the glass on my NuArc--like Newton Rings.

Has anyone else ever had this problem?

 

[Jeremy]

Just for clarification - you're seeing this with 'premium' OHP cut from rolls vs the 'sheets'?

Yes. This is a 13" roll of the "new" OHP (Ultra Premium Fantasticamatic or something). Haven't been able to make it back to my studio yet this week due to work, but hope to be over there very soon.

 

[SusanV]

Hi Jeremy,

I'm familiar with what you're describing, and have the same thing happen with OHP (sheets), and my Nuarc's glass. In my case I've come to realize (after much testing) that the newton's rings didn't cause the splotches, it was the inked OHP bonding to the surface of my plates, not allowing all the air to escape out to the sides and be evacuated. After much experimentation by myself and others doing this process (photogravure), this is what's working for us...

Be sure the ohp and your paper are REALLY dry. Even when exposing ohp that's days old, I still heat it up with a homemade drying cabinet for about 10-15 minutes before an exposure to pull out any moisture it has absorbed. If possible with your process, you can do the same with your coated paper.

Use baby powder or talc between the ohp and your surface. Sprinkle it on, and then use a soft brush to remove most of it. You can experiment with using it on your surface, and/or on the ohp. The talc particles are small, but air molecules are smaller, and can escape your entire surface and be drawn out by the vacuum, giving you better contact.

hope this is helpful... report back and let us know how it goes for you.

Susan
ps... the gravure folks call these splotches "measles" )

 

[BillSchwab]

Great tips Susan... thanks!

Bill

 

[Jeremy]

It is w/o a doubt happening b/w the ohp and the glass. i watched as i raised the psi and more of them appeared. i turned the vacuum off and the ohp was stuck to the glass and the distortions were still there. i took a snap w/ the digital of the interference pattern. i think it's being caused by moisture in/on the OHP.

 

[Jeremy]

This is a picture showing the interference. As I *need* to get these images printed I have switched to just setting my contact printing frame on top of the Nu-Arc for the time being. No interference pattern in the contact frame.

 

[Jeremy]

I am incorrect, I was able to reproduce the interference patterns in the contact frame by the sandwiched paper very hard up against the glass. I have tried using the hair dryer on max for 5 minutes to dry them, but still no-go. Next I'll try 3-4 psi in the vacuum frame and see if this is low enough in addition to 10 minutes of hair drying to fix the problem.

I believe it is related to moisture as this has only happened in the last 1.5 weeks and the humidity here has been much higher than usual.

 

[Jeremy]

I am getting interference at 2.5 psi (according to my 26-1k's gauge).

 

[SusanV]

Jeremy,

Yes you're having a different problem than I thought, but it's also a problem I'm having as well. Check out my thread here about Nuarc, Newton and OHP for the discussion...

Susan