Polyester Plates Inking Problems

[peewee]

Hi,

Just started using novadom polyester plates on a small A4 Rotaprint litho press. Got real problems inking - the plate seems to pick up background ink real quick and no matter how much damping I use it doesn't help.

I've checked the ink rollers pressure. I've tried using novodom fount & standard litho solutions.

Any ideas?

Signed,

Desperate & filthy hands

[kyprinter]

PeeWee,
I assume that you are talking about Novadom Laser plates, if not or if you are already doing the things I'm going to tell you then just ignore this post.
First, is the problem of toner scatter. Look at your plate with a loupe to see if there are tiny specks of toner in the background. These will need to be removed with laser plate cleaner (check with your plate supplier). I started out with the LaserMaster Unity for outputting laser plates and the excess toner was so bad you could never get rid of it. I switched to HP 5000 and this is no longer any problem.
Next, these plates need to run wetter than most other plates. Always wet the plate well before starting up even if you just stopped the press for a very short time.
Last, search this forum for laser plate related posts. There are a lot of good tips on here and one user has even made a tip sheet and will email you one if requested.

[peewee]

Ky thanks for replying,

Yes novadom laser plates, imaged one side and I'm sponging the plate to wet before running, I've tried damping from light right up to max and still no joy, using light ink. The plates seem clear from scatter and my laser printer (Oki 510 dn) is brand new and prints real crisp and clean.

The only thing I haven't checked is PH of fount which I'll do tomorrow when I've got some test strips. I'm even using the novadom fount and plate cleaner, blanket wash is water based though not novadom should be fine. I use it for letterpress too.

Another possibility (which I'm not sure as the plates are new to me) I'm using standard four colour process inks from Litho supplies - don't know if that's a problem or not. Maybe Vanson is better? I don't know.

I'll try and find the link to that tip sheet - sounds helpful.

Thanks for your help - I do appreciate it.

Pete

[voltage]

Try using some Van Son ink if you have it. It seems to work well with laser plates while I've experienced some other random ink not working well and doing things similar to what you're experiencing. At least you'll know that the ink is not the problem if you keep having these issues. I think you can get a can of black Van Son ink from a distributor for less than $5 so it shouldn't be a big investment if you don't already have it. Stick with oil-based ink. Is your novadom fount the kind with a 1:49 ratio?

[peewee]

Hi voltage,

Thanks for your help. I do have some black Vanson ink I'll give that a go, I'd happily replace my inks if that's the problem. I am using the novadom fount solution at recommended dosage & tried stronger solution too. I think my PH may be a little high in which case I'm going to use some citric acid to soften my water then make up the fount solution.

New day today, I'll try all these things and post back what happens!!

Thanks guys.

Peewee

[voltage]

If you want to eliminate more variables you could try using distilled water from the supermarket. I know many people say distilled water is unnecessary but tap water will probably cause problems in some areas. I can't speak with authority on those problems as I've never experienced them. I mention this only because you're concerned about the pH which in this day and age is something one shouldn't have to think about with all fountain solutions now being "buffered" to pretty much give you proper pH all the time.

[peewee]

Hi,

Well PH of local water is 7, when I added correct dosage of fount solution PH came in at 6, still to high. Using citric acid I've brought PH down to 4.5 and cleaned the damping rollers and today ran a clean plate! Even doubling the fount solution it still wouldn't bring the PH down.

Was it the PH? I presume so. Plus a careful balance with the ink & damping. I only ran setup's today but aim to run two plates on Wednesday and I'll post back.

Thanks Guys.

[peewee]

Oh... the other thing is to sponge the plate with fount solution before every start up!!

[Green Printer]

The University of Illinois at Springfield is all poly plates. I talked to Mr. Tom Slate and he said he use to have all the problems you are describing. Tom suggested getting in contact with BestChem & Supply.

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