Gas/Gloss ghosting with Aqueous coating

[bhm8hwcm]

I am running a Presstek 34 DI machine (4 colour) printing gang run business cards, postcards etc. Up until a few months ago I was printing a flood varnish, but I then switched to running an ink train AQ gloss coating. It has worked great and the drying time is much better than the varnish.

I recently switched from running a 12PT gloss cover to a 14PT gloss cover...same brand of stock, just thicker. On the last couple of jobs I have run, we have been getting gas ghosting on the first side of the AQ that we print. The gloss of the AQ is less wherever there is heavy ink coverage on the reverse side of the sheet. If there is light coverage on the back then the gloss is high. We are not ghosting in the printing of CMYK, only ghosting on the AQ first side. We back up the AQ pretty much right away and we do not ghost on the second side I assume because the front side AQ seals everything.

I have tried reducing the IR or turning off completely (usually I run low IR on first side and then turn off on 2nd side). I printed the AQ on a job that sat for about 24 hours as well as one that sat only for about 4 hours and the results were pretty much the same. Turning the IR completely off helped a bit but it is still there a bit.

Any ideas? So far things maybe are pointing to the change of paper as I can not see what else would do it. I do not usually run the press much anymore as I have a new pressman. He seems to keep his delivery pile quite tight and the sheets seem to deliver hard. Could this be slowing ink drying and trapping escaping ink gases?

 

[Bob Peterson]

Re: Gas/Gloss ghosting with Aqueous coating

Barry,

Gas/Gloss Ghosting is usually a function of the oxidation process in caused by high solids inks i.e. (Low VOC) in conjunction with excessive drier loads i.e. (Cobalt & Maganeese). Also, Press room conditions, paper, and quick turn around times.

I have a white paper that was done by GATF pertaining to gloss ghosting causes and cures that I would be willing to email to you if you would like as it is too large to attach to this message. Let me know if you want a copy.

Regards,
Bob

Edited by: Bob Peterson on Jun 19, 2008 9:31 AM

 

[bhm8hwcm]

Re: Gas/Gloss ghosting with Aqueous coating

Hi Bob thanks for the help.

Yes if you could please send me a copy of the white paper that would be great.

You can email to [email protected]

Thanks.

 

[Amer Hasan]

Re: Gas/Gloss ghosting with Aqueous coating

This is a hot topic these days. If you can email me that white paper to my attention that would be great. [email protected]
Just had this problem occur on a 10,000 sheet run of 100# dull cover. Went to the press ok - no problem. By the time it got to the lettershop. ghosting on 1/2 the background. Light Pastel color PMS 7452

 

[csmith]

Re: Gas/Gloss ghosting with Aqueous coating

I would also appreciate a copy of the white paper. We have had a couple of jobs on our CD102 go south recently due to gas ghosting.

Regards,
Chad Smith
[email protected]

 

[ian]

Re: Gas/Gloss ghosting with Aqueous coating

can you please email me a copy of it too.. we have a DI and have the same problem, our temporary fix was to buy a UV coater

thanks
ian
[email protected]

 

[bhm8hwcm]

Re: Gas/Gloss ghosting with Aqueous coating

Thought I would follow up since my original post. I continued to have my ghosting problems for a couple of weeks and tried a number of different things but nothing seemed to solve my problem. Then one day I may have solved the problem unexpectedly...or atleast temporarily.

In my opion it seems as though I may have been running too "cold" in the delivery. I have my press in an air conditioned room. A little while back (maybe around the time I started having problems) I put in an exhaust fan and more AC (use both dependent on conditions) and overall I have been having better results controlling my room temperature. Recently though my room got very hot and when I ran the AQ I noticed I did not ghost. I have a thermometer in my press delivery and the temperature was up around 45-50 celcius in the delivery (Canadian). Becuase I was still trying to sover my problems I paid close attention to everything I was doing and the only thing different was the hot temperature. Anyway I was happy I did not ghost.

The last couple of times I have done the AQ I have let my room temperature creep up, and I have started cranking my IR up to increase the overall temperature in the delivery. So far I have not had ghosting.

When I was having my problems I kept thinking the IR heat may be causing problems and so I was running it very low and even running without it at all thereby keeping the delivery temperature low. By running it much hotter perhaps the jobs are drying much quicker and therefore not allowing time for the ghosting to happen...just a theory.

Apparently pile load temperature is important but I don't have a probe to properly measure it. I will keep running hot as long as it works.

Good luck.

 

[Paul Hastilow]

Re: Gas/Gloss ghosting with Aqueous coating

Hi there,I have been following your discussion with interest,pertaining to Ghosting.
I am Production Director for a Print Finishing House in Cape Town South Africa.
we are in our Winter season now when all our drying problems appear.
A customer of ours has had a problem with ghosting on Magazine covers he sent to us for Spot Gloss UV varnishing .
We first put a textured matte uv down and then spot on top
when the job arrived from them there was slight evidence of ghosting on the back/inside pages where there was a heavy solid black advert.
The reversed out type on the front cover and the Bar code was the ghost image on the inside cover.
To save the job we ended up doing a satin matte uv varnish as a spot (leaving the glue spine open)
this is obviously expensive and time consuming for the customer.
We have experienced similar phenomena from 4 or 5 customers of late,and the ONE common denominator was the ink used.
The ink supplier is trying to sort out the problem (but where to start!)
we know that the heat from the uv lamps makes the problem worse,wheather through "Gas Ghosting" or "Migration" of mineral oils to the otherside of the sheet ,released due to the heat.
any suggestions as to the correct sequence to proceed to overcome the problem for the printer. Bearing in mind the covers are printed on an 8 colour press ,one pass. how long must we leave it before finishing.(deadlines permiting) what colour sequence is preferable.and what inks did you use when the problem arose.
best regards
Paul Hastilow

 

[Paul Hastilow]

Re: Gas/Gloss ghosting with Aqueous coating

could you please e,mail me a copy of the "white Paper" concerning Gas Ghosting as compiled by GATF
regards
Paul Hastilow

 

[Indexx Printing]

Have any of you guys ever tried K&E waterless Ink? I have run it on a DI with great results. I have Also ran Tanaguchi with similar results but am not a great fan of Asian Ink. Both of these inks perfromed well and even with AQ coating I never had a problem with ghosting. However temperatur of the roller train and the emviroment are big time issues in waterless printing. Just my 2 cents.

Todd

 

[tim253]

could you please e,mail me a copy of the "white Paper" concerning Gas Ghosting from GATF.

Thank You

[email protected]

 

[madjock]

I would like to say that I have seen gas ghosting more times than I care to remember, but never once have I seen it on a job with in-line aqueous coating, in fact I have been led to believe that conventional wisdom says that coating almost completely elliminates gas ghosting.

 

[Komoriopr]

In my experience you are right on the money about temperature. Run your first pass at 100 degrees fahrenhiet and your 2nd at 90 to 95. Your stock dictates the amout of IR but usually 40% on light stock is sufficent. Aqueous cures thru evaporation so your hot air knives are very important. I run those at 85%. if these don't solve the issue consider changing your AQ. vendor.The polymer in your current vendors AQ may not be correct for your enviornment. these temperatures hold true on varnishes as well. As for methods to measure with, a simple meat probe slid into the side of your load will work.

 

[Denny]

Bob,

I would appreciate you also sending me a copy of the white paper that was done by GATF pertaining to gloss ghosting causes and cures. We've had our first ghosting issue with aqueous coating in years and forgot some of the basics. Please send it to: [email protected]

Many thanks.

Denny

 

[aqazi81]

Please email me a copy too at [email protected].

Regards

Asif