Ghosting has me stumped

robbg439

Well-known member
I'm running a job on carbonless in two passes on my 2 color ryobi. First pass is black and a spot (pantone 292). As I'm running the second pass (two more hits of black, this is a weird job), I'm getting weird repeated ghosting of a mark I printed in the pantone during the first pass. Its a regular, repeating ghost above and below the mark (see attachment). It seems to come on very gradually after a couple hundred sheets. Nothing else on the page printed in the spot color are having this problem. Its an easy enough problem to solve (just clean the blanket every couple hundred sheets). I am mostly just curious as to what could be causing this, as I've never had anything like it happen. If the mark were wet, it would be hitting the blanket in the same spot on the blanket on the second pass, so I can't figure out why its repeating like this. Any ideas?
 

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gordo

Well-known member
I'm running a job on carbonless in two passes on my 2 color ryobi. First pass is black and a spot (pantone 292). As I'm running the second pass (two more hits of black, this is a weird job), I'm getting weird repeated ghosting of a mark I printed in the pantone during the first pass. Its a regular, repeating ghost above and below the mark (see attachment). It seems to come on very gradually after a couple hundred sheets. Nothing else on the page printed in the spot color are having this problem. Its an easy enough problem to solve (just clean the blanket every couple hundred sheets). I am mostly just curious as to what could be causing this, as I've never had anything like it happen. If the mark were wet, it would be hitting the blanket in the same spot on the blanket on the second pass, so I can't figure out why its repeating like this. Any ideas?

I don't know the vagaries of your press, but typically, ghosting like you seem to have can be caused by over emulsification of the ink (the fuzzy edges of the type suggests this). The ghost image may occur at a distance of exactly one form-roller’s circumference away from the original and corresponding image.
 
D

Deleted member 16349

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I don't know the vagaries of your press, but typically, ghosting like you seem to have can be caused by over emulsification of the ink (the fuzzy edges of the type suggests this). The ghost image may occur at a distance of exactly one form-roller’s circumference away from the original and corresponding image.

Gordon, if I understand the original post, the ghosting is happening in the printed pantone ink of the first pass, but it is happening during the second pass. Something strange is happening.

Maybe the original description of what is happening is not clear.

If on the second pass, the pantone ink is still very thick and wet, I could see it going back onto the blanket and up onto the plate, if the plate is almost dry and then be picked up and ghosted by possibly a dampening roller contacting the plate. Since it also comes on gradually, this seems to support such a possible cause. For sure not the normal ghosting. Other than that, I have no other ideas.

I am not sure about the issue of how the black is printing. It may not be the issue since the post is mainly taking about the pantone. Maybe the original poster can comment on the text being so bad and if that is related to his problem.
 

robbg439

Well-known member
The ink film isn't thicker than normal and I left the prints to dry overnight before I did the second pass so its not especially wet either. As you can see in the image, the ghosting begins a lot closer to the original image than the circumference of the form roller and then repeats at regular intervals. The black text is printing totally fine and the first hit of black isn't ghosting during the second pass. (also sorry, I should have explained, this job has three different texts in black printing right on top of each other so it supposed to look unreadable like that, like I said its a weird job to begin with!). Also strange is that everywhere else that the spot color was printed on the sheet isn't ghosting like this (I lucked out there).

And yes, Erik, you are right, the ghosting is happening during the second pass to an image that was laid down on the first pass. Come to think of it, thats also weird, since I laid down the pantone in the first unit, so why didn't it ghost like this on the second unit during the first pass, when the pantone was really wet?!?

If the water form rollers were the source, I feel like I would be able to see the blue text ghosts on the form rollers after printing for a while, but I can't. The ghosts only appear on the blanket and on the prints. Its so weird! Could it have something to do with the carbonless paper?
 

Alois Senefelder

Well-known member
Puzzled..........


1) The Pantone Spot colour - you are printing with "Emulsified Ink" 2) ARE you talking about the "Doubling on the Black Text" Ghosting is a different problem !

re the Paper..... forget that


Regards, Alois
 
D

Deleted member 16349

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The ink film isn't thicker than normal and I left the prints to dry overnight before I did the second pass so its not especially wet either. As you can see in the image, the ghosting begins a lot closer to the original image than the circumference of the form roller and then repeats at regular intervals. The black text is printing totally fine and the first hit of black isn't ghosting during the second pass. (also sorry, I should have explained, this job has three different texts in black printing right on top of each other so it supposed to look unreadable like that, like I said its a weird job to begin with!). Also strange is that everywhere else that the spot color was printed on the sheet isn't ghosting like this (I lucked out there).

And yes, Erik, you are right, the ghosting is happening during the second pass to an image that was laid down on the first pass. Come to think of it, thats also weird, since I laid down the pantone in the first unit, so why didn't it ghost like this on the second unit during the first pass, when the pantone was really wet?!?

If the water form rollers were the source, I feel like I would be able to see the blue text ghosts on the form rollers after printing for a while, but I can't. The ghosts only appear on the blanket and on the prints. Its so weird! Could it have something to do with the carbonless paper?


Yes, this is a weird problem. Of course there IS a rational answer but it might be that we will not find out what that answer is. The problem might just go away.

OK, back to the issues. You say the pantone ink was dry but you also said that it was ghosting on the blanket during the second pass. If that is correct, that means that is was not totally dry and could transfer ink to the blanket and probably somewhere else in the system.

In looking at your photo, I see about 4 ghost images. Equally spaced before and after the printed image. When one is talking about ghosting and circumference of rollers, one needs to look at multiples of the rotation of these rollers in relationship to the plate/blanket cylinder. So it is not just a matter of measuring the distance from the original print to the ghost but one has to calculate where that ghost image would go on the next or even the next few rotations.

In trying to find the ghosting roller responsible, one can do some calculations. Take the circumference of the plate cylinder and add or subtract the distance from the printed image to the ghosted image. Then take that total (both the added and subtracted result) and divide by the circumference of any of the rollers touching the plate. You are looking for an answer that is an integer, such as 1, 2, 3 etc. If you don't get an integer as an answer, then that roller should not be the one causing the ghost. This could get complicated if the ghosting pattern is due to additional rollers in the roller train but I would not expect this to be related to your problem.

Ghosting usually shows up in a solid printed area but your problem of multiple ghosts shows up in the non image area. Very strange.

If there is something strange about that pantone ink, one could print with some other ink in that unit and see if it also ghosts. If it goes not ghost, then maybe there is something strange about that pantone ink. If it does ghost, then this suggests something strange about the print units.

The fact that you don't get ghosting for other pantone printed images in other areas might just be due to luck in that maybe the location of those non affected printed images are close to the large gap in the blanket and plate cylinders that have changed the results. Strange indeed.

I can't think of anything more just now. I do hope that if you do find the solution, that you let us know. Good luck.
 

Alois Senefelder

Well-known member
Now the veil as been lifted from my eyes !!


What we are seeing are Roller Repeats, Erik pointed out there are 4 repeats... 2 before the Image - 2 after.

Check all your roller settings..... emulsified ink is a problem you have.

The Mechanics of this problem, begin with the roller repeats -- Sensitizing the Plate, Clean the Plate and Gum-up also

check your F.S. Chemistry is correct.


Regards, Alois
 

Alois Senefelder

Well-known member
For my next ............

OK - now measure the distance from the Grip Edge to the first Repeat ... (mm), divide the distance by 3.14 (Pi) this rough calculation will give

the suspect roller diameter


Regards, Alois
 

Cornishpastythighs

Well-known member
It could be that the blue ink is transferring off of the sheet to the blanket and then to the plate and causing the plate to become sensitive this ghost image would then be picked up by the rollers and deposited back on the plate then to the blanket and back on the sheet which accounts for the different positions of the ghost images.
I know I've lost the plot but its all I can come up with.
 

robbg439

Well-known member
why not stack the three layers of black text in prepress and do in one pass?

Printer does as client wants!

In response to Alois, the first repeat is actually right up against the gripper margin.

I was unable to repeat the problem when I did the same procedure to the other side of the sheet. I have to blame the weird clay coating on the one side of the "CFB" carbonless sheet. Although I still don't understand the mechanism of the repeating ghosts, I know it must have something to do with this coating, because the ink on that side of the sheet still isn't completely dry and will will smear if you rub it.
 

old guy

Well-known member
look at your feeder roller i bet you are picking up ink there and "reprinting" down the sheet until it lifts. try backing off the presure.
 

robbg439

Well-known member
If that were the case then cleaning the blanket wouldn't help, but it fixed the problem for another couple hundred sheets. Also it would seem that if the image were being picked up by the feed rollers, the repeats would run all the way down the sheet rather than twice above and twice below the original image. Finally, my machine has its feed rollers on the underside (non printing) side of the sheet.
 

old guy

Well-known member
the feed rollers pinch the sheet to push it into the infeed cylinder grippers they release about 3 to 5 inches down the sheet depending on how tight the buckle is set. if ink is transferring to the top roller and offsetting back onto the sheet it would transfer to the blanket also from the sheet itself. since you are running only black on the second pass the blue images must come from the sheet. If there was any kind of sensitizing of the plate the black ink on the rollers would make the ghost images black.
 

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