Chrome roll sensitizing

I just started operating a 02' komori 28 lithrone. The chrome roll is picking up ink when running pms reds but not magenta.After wash up they apply an etch solution to the roll. The shop uses Four Star fountain solution 2.5 oz. and hydro plus alcohol sub 12oz. and 2 oz of Allied dryer per 5 gals of water. Any advice would be helpfull. Thanks

 

Sensitizing often occurs when the hydrophilic layer on the chrome is broken down in some way Are the inks you having the issue with, by the same manufacturer as the standard cmyk set? Are they vegetable oil, petroleum or rubber based? Are the recirculator and water pans clean? Do you have infra-red dryer? If so why do need to put additional dryers in the fount? Is this a new problem or a recurring one?

By etch - do you mean gum arabic? Normal action we would take assuming all the above check out OK.

1 apply gum arabic after every shift - leave overnight
2 if you still get ink picking up - try mrc or equivalent (metering roller cleaner) directly to the chrome - apply gum and leave to dry

If you still get this issue you may need to change ink or fount. We get great results from VARN products but you need to check the quality of your incoming water supply.

Have you checked ph and conductivity of the fount solution?

Hope this helps...

 

We have the same issue on some PMS colors. For us there were 2 solutions. Which one you ise depends on which cause was the issue. For some colors this issue stopped just from adding an extra ounce of etch per gallon to the fountain solution, thereby cleaning the ink from the chrome roller on the fly. Careful not to use too much though. Also make sure that you clean it more thoroughly when you stop to clean it. We use a special CHROME ROLLER CLEANER ( Prisco ) and then we apply pure gum arabic to the chrome roller and allow it to dry. That will keep it from happening as often even if you don't add extra etch. Also...of course....make sure your fountain solution is not contaminated with any solvents or cleaners.

 

I had the same problem a few years ago. Alcohol is your problem. Alcohol and it's substitute are for lowering ph. 12 ozs is an obsene amount! 1 to 2 ozs. is normal, 3 or 4 is the most you should ever try. Time for a different fountain solution if you ask me.

 

Err? Alcohol is for lowering the surface tension of the dampening film not for controlling ph. PH is controlled by, usually, buffered fount additives.

We found that 2in1 Fount eliminates the need for fount additive and for IPA.

We were sceptical at first (based on our experience using an alternate alcohol substitute that didn't work for us) but 7 months in andd we're well impressed with it. A fount solution that actually lives up to the claims!

Didn't ever think I'd be enthusiastic for a fount additive but there you go!

 

I also use the prisco chrome roller cleaner, its excellent. Normally put it on the rolelrs on a friday after washing up, once a week.

 

I second that. Which PMS ink is it? Some PMS inks have different ingredients that might conflict with the etch you are using. We had issues with our Magenta taking ink on the chrome and metering, and rollers going blind for a little while in the spring, come to find out that the ink supplier had switched ingredients and didn't notify us. There were conflicts between the etch and the new ink. We ended up changing out the etch.

 

It sounds like a back trapping issue. Use to encounter a similar problem on the magenta unit at high speeds. Always blamed it on the chemistry, temp. etc... Gummed the chrome roller till I was blue in the face. Finally solved the problem, their were minute scratches on the chrome roller causing the initial ink build up and on top of that, the chrome to water form setting was a little too tight on that particular unit. Remember, lighter the stripe or nip more transfer. There's a fine line in the water system though but you have to play if you don't want problems. I'd be willing to bet that you have an imperfect surface to your chrome. You can throw all the cleaners and fountain solutions at it that you want but I feel that you have a mechanical issue.