Four colour process colour sequence

[Paultheprinter]

Does anybody run Magenta before Cyan, if so have you ever experienced any problems with the yellow pulling the cyan into its duct?

 

[Green Printer]

Re: Four colour process colour sequence

Tack sequence is what matters. 1 to 2 points tack difference between each color in sequence.

This occurs in any printing process with a wet trap.

On aluminum cans the colors do not touch in a wet trap printer or the colors will contaminate

On a dry trap usually this is not a problem

Unitac inks can work if the service layer of the sequence has tacked up enough to accept the next ink.

When tack sequence is out of order inks will partially be pulled off of the sheet and contaminate the next color down.

For instance

say your magenta has a tack of 12 and your cyan a tack of 14. The cyan will have trouble adhering to the magenta and the next blanket will tend to pull some of the cyan off of the magenta and contaminate the next color in the sequence.

Pat Berger

 

[gordo]

Re: Four colour process colour sequence

Switching the cyan/magenta units is sometimes used as a fix to hitting blues and purples for specific jobs where the press is having problems with those colors. Laying magenta down before cyan will distort your color space - it can have a dramatic impact on color. Blue skies, for example, will be more purpley - skin colors may look like road rash.

best, gordo

 

[dremaley]

Re: Four colour process colour sequence

For color, the 'correct' sequence is C-M-Y / Black can be first or last. This sequence was studied by PIRA and others. The 'color' of Reds are better with this sequence but the greens are not. If you change the sequence the green becomes better but the Reds are lousy. We're more sensitive to Reds than Greens.
Dan

 

[madhura mahajan]

Re: Four colour process colour sequence

I have printed with a sequence of K,C,M,Y. 'K' is Black unit. We have experienced excellent trapping of green but poor trapping of red. So does it mean that yellow has been contaminated with magenta. Not because of tack but due to very short span between magenta and yellow that resulted into poor drying of magenta.

 

[gianotten]

Re: Four colour process colour sequence

This is not a reply to your last question. However, let me make some remarks. The sequence KCMY was used to generate the Output Conditions or Characterization Data. This public information (www.color.org) was used by ECI, Adobe and others to generate their specific profiles such as ISOcoated_v2_300. It was made from Fogra39 characterization data. These profiles are used by your customers, designers and most probably your own in-house prepress department.
The secondary colors depend on these profiles. By changing the sequence you break the chain. Color Management by ICC profiles is possible due to the fact that we agree on standards. The sequence is part of the ISO 12647-2. One can only change the K. Dan already explained that. So KCMY or CMYK is the sequence for sheet fed offset and heatset web.
The "Output Condition" in application software such as Illustrator, Photoshop or CS2/3 is very important. It determines the other views of CMYK. Hard- and softproofing depend on the profiles and sometimes on the Device Link Profiles to simulate output CMYK on other media.

 

[Paultheprinter]

Re: Four colour process colour sequence

Thanks everyone for the input, we have ran the sequence magenta before cyan for years and this was ok until the last six to nine months, but recently the yellow has pulled the blue into its duct and sends it green forcing us to wash the duct when it becomes unacceptable.

This problem started after rejuvenator was used in the auto roller wash and i am trying to find out if this trapping problem is something due to the sequence or the condition of the yellow unit rollers. The hardness of the rollers is 35-40 shaw a and the rollers do look shiny but when i reduce the tack of the yellow the blue still traps back?

All help appreciated

Paul

 

[Caled]

Re: Four colour process colour sequence

We run CMKY with yellow being last in the sequence. This stops any "muddying" of colours if your press has common impression cylinders.

 

[ian]

Re: Four colour process colour sequence

We have trapping problems with yellow.. anyone know of a solution
The issue we have is KCM are low tak and yellow is medium tak, if we use lowtak yellow then we get toning because of the IR dryer

 

[Paultheprinter]

Re: Four colour process colour sequence

HI, the inks should always run softer as you head towards the delivery, so if there is no option of reducing the tack of the yellow the only option would be to increase the tack of the three previous colours, or investigate why the yellow is toning and reduce or cure this.

 

[rbailleu]

Re: Four colour process colour sequence

put in more fans to suck the heat away from yellow. or put in an insulated plate over the ir dryer. or add another cooling unit to the yellow inking unit.

 

[Atlee Yarrow]

Re: Four colour process colour sequence

I liked all the different ideas placed by others, I however have never tried M before C and agree with the order KCMY. I will point out that I have run Heil. 102 F to AB Dick 9810's without a problem in four color process either one, two, or four colors at a time. My solution is being clean and detailed first with three color washes if need be (common blanket on smaller presses) and the pumice wash/scrubb. Then I follow this by thinning the Y down ever so slightly being careful not to spread the dot (user beware). I like to think gravity helps me here as water seeks its lowest point. Lastly I am absolute in the pressure between the blanket and cylinder as not to over squeeze paper and dot.

In more extreme cases I've been known to use patch blankets and/or take the rollers out for manual cleaning to adjusting stripes. Basically I do whatever it takes to make the customer happy and comming back.

Edited by: Atlee Yarrow on Dec 24, 2007 5:47 AM

Edited by: Atlee Yarrow on Dec 24, 2007 5:49 AM

 

[John]

Re: Four colour process colour sequence

Most pressman will change sequence from kcmy to kmcy when they are trying to match a screen tint match. In this case, the combination of c&m. A lot of times the cyan is almost always solid with a tint of magenta. Running magenta down first makes this combination look better because of trap. Ink traps better to paper than it does to ink. The yellow becoming contaminated could be a multitude of problems. Tack of inks, ink/water balance, condition of rollers in the yellow unit, and even pressure between blanket and plate and/or blanket and impression cylinder. Of course roller settings in the yellow unit are important.