Ink feeding back into dampers on spot colours

Hi Guys

We are having this problem on our Ls29 where when we are running heavy coverage spot colour jobs we get ink build up on our chrome and pan damper. I have seen a few simalar threads but with slightly different symptoms. We don't have any issue at all running process colour jobs and it isn't every spot colour either. We have talked to the ink manufacturer and he has tried adding aquapel to the mixes but this hasn't helped. There dosn't seem to be a pattern to the colours it is doing it on. Some times it has feedback by the end of the makeready sometimes a few thousand into the run. We had a job the other day where it was binding up badly after 1000 sheets so we tried mixing the ink here out of the same manufacturers bases and we then ran the rest of the job (15000 sheets) with no problem! We are running 2 percent combifix XL fount and 6 percent alcohol. I was thinking a bit more alcohol may help?

Any ideas much appreciated

Cheers in advance

 

try to desenseitise your chromes . with chrome cleaner and the n a mixture of fountain soloution and gum arabic
not the crap they use in the plate room use aclean sponge and go over the chromes for ten minutes everyday for one week.

 

Hi Spike, we have been doing that and it keeps it clean temporarily but it dosn't seen to fix the problem. If it was just a problem with the chromes senseitiseing up wouldn't it do it on any inks?

 

litho 1
I have have been running without alcohol for decades and all the issues I read about, I don't have, why? Alcohol dries out the rubber rollers, breaks down the ink, causes blinding on CTP plates, and is not good for air quality in the pressroom. Yes when you run alcohol free you have to set the roller with good strips, but your rollers will last longer and not shrink. Would you consider changing to a phosphate free etch and no alcohol(prisco 2451 plus 2), if when your putting new rollers in your damps that is when you can change over. In this town i would say only 2-3 % of the printer here still use alcohol, the hardest part of change over is getting the operator to stop thinking that you need alcohol to print. At this point for you your chromes are getting damaged by rollers that are turning into grind stones from running alcohol.
FSA

 

Hi Litho, Why are you only running the fount at 2% maybe try 4% like it says on the bottle ;-). I still think adding a little more alcohol(maybe to 8%) would help not hinder and won't change your press room conditions by much (but increase the fount first). And your going to have to monitor the weather and see if your issue starts getting better as weather improves over coming weeks.Your water supply will harden over summer and should improve things a bit. Chat later
Daz

 

litho 1 have you trired to decalcify your rollers some inks willreact diffrently from others to calcium for instance
the red unit is more likely give you a problem toning /stripping /feedback ect. you said the problem only happens on spot colors mayby you need to see how hard yourwater is. there are diffrent pigments in spots that are more sensitive to calcium and other minerals/ive been through this before its going to be a procsess of elimination good luck

 

Hi, to maintain a desensitized damper you should increase your fountain solution. If you have a conductivity meter, you should check your conductivity level and try and maintain 1500-2000ppm. I am aware that your process colours are ok but they may not be as affected as the spot colours especially with image that requires a lot of ink like a solid.

 

Hey,

We had a lot of the same issues you described. Do this simple test to determine what your next direction is:

Your first startup of the morning (or after washdown), before you engage your dampening system and everything is still clean, take a sponge and wipe the chrome roller with a little bit of gum arabic. If there is any greasy residue still left on the roller you will see the seperation right away.

We had to find this out through some trial and error, but sometimes there is a little bit of residue that you wont be able to see that is still on the chrome roller, no matter how good you wash-down. If you wipe your chrome roller over and there is no apparent spots that are not picking up water, then you can start looking in to the more complex remedies.

 

Hi Guys

Thank you for all the advice. Yes Spike we do decacify the rollers regularly. We know our water is a bit on the soft side which is why we don't run alcohol free.very few do in our part of the world. kaoticor the chromes seem fine but our conductivity may be a bit low so our first step is to tweak a bit more fount and alcohol and see how that goes. I will catch up tonite Daz.

Cheers

 

Seems to me the problem may be related to your supplier if you mixed in-house and ran problem free. Do you encounter the problem every time you use supplied PMS colours?

 

Hi Grant

We don't have the problem on all of the supplied pms inks but if we are going to have it it is only on certain supplied pms inks and usually when running heavy coverage. We do think there is an issue with what we are being supplied and are working with the manufactuer but want to make certain we are doing everything right on the press.

Cheers

 

does this problem occur when your running a weakly pigmented ink? Ive found that alot of ink manufacturers are mixing their inks on the weak side.When an ink is weak in pigment you will have to run a thicker film on your rollers to arrive at the same color. There are times when you can increase the strength of an ink in house. For example.... If an ink has transparent white in the mix just try reducing the percentage of transparent white so that you are running something a bit stronger. You should then be able to reduce your ink fountain feed and maintain the same color with a lower ink feed ,and a thinner in film on your rollers. If you find that this cures your issue of ink working back into your dampener then its time to give some thought to trying a new ink supplier. Ive spoke on here often of a trend ive noticed over the last dozen or so years where pms matches are being mixed on the weak side. Its a little more difficult to do on process colors as there is more of an industry standard to answer to.

 

If it is random pms colors
Look at the mixing products in the
Pantone book and c if there is a
Pattern. We had a similar problem
And discovered it was the mixing yellow
We also noticed it would be worse
If the density was screaming
There was just no where for the ink
To go

 

There is a problem on a certain cardboard. Simply I change inks for other producer..