Colour Sequence...

[Disappointed]

Hi all,

What difference does colour sequence make to a job?

I know it does make a difference as a print engineer proved it with a hard-to-match purple when he swapped the Cyan and Magenta around and it worked much better.

We are still printing K – M – C – Y as he left it but what would Y – M – C – K do to the jobs?

The reason for asking is that since swapping C & M we get better purple and blue hues but also suffer very bad yellow contamination with cyan.

My suggested order would prevent any risk of contamination but I don’t want to risk it if it’s proven to be a bad idea.

Any views?

Dave

 

[spigot]

id be looking at talking to the ink rep first about it, maybe changing brands or changing to a mix that has a yellow that doesnt want to pull back so much. Failing that, and depending on what kind of work you do, i used to run c-m-y-k on an older press that had doubling between units one and two, this sequence worked fine for a couple of years.
I would not put yellow down first if i were you!

Also, how good is the prepress there? I assume the purple you were matching wasnt looking "blue" enough? Maybe have a look at what screening was under it, and other factors that go into the job before altering colour sequence. Mainly because if you swap inks to fix a problem, you may cause yourself another later.

 

[nhprinter]

Hi Dave,

If you want to run your yellow first and your black last you need to order a "first down" yelllow and "last down" black so that the tacks can be corrected to run in that order. That will prevent any contamination. The tacks on the magenta and cyan are the same most of the time so you can swap those between each other anytime, but if your presses are "profiled" you could have a hard time matching your proofs.

Dave

 

[Disappointed]

Thanks all,

point tested, the light coverage jobs look good but dark ones do not as the black does not trap onto the other colours.

Interesting test but fruitless in the end.

Thanks again

Dave

 

[Laxmi Kant Kuthiala]

Wet on wet trapping is what causes the shift in colour. The second ink in a wet on wet will always transfer less efficiently. So if you want a blueish purple print cyan first, and if you want a magentaish purple print magenta first. You could also reduce the tack of the second ink to get a better transfer

 

[HachiZenki]

Well what kind of press are you running? We're running 4-HI's with the Y-M-C-K config. and it's fine except for some contamination of the yellow with the magenta.

 

[gordo]

Well what kind of press are you running? We're running 4-HI's with the Y-M-C-K config. and it's fine except for some contamination of the yellow with the magenta.

ISO says that the ink sequence should have the chromatic inks laid down in CMY sequence with K being either the first or last ink down. Often Y is laid down first (with K last) in newspaper work because in a traditional color separation there is usually a great deal of Y coverage. So, it acts a bit like a varnish and helps to seal the paper and provide a better surface for the chromatic inks. Also, in newspaper work, K is usually a poor quality ink. It is usually laid down last since if it is laid down first it could cause contamination of the chromatic inks following it.

On a sheetfed press, laying Y down first (if it's a traditional color separation) will usually cause trapping problems with C next down (i.e. poor greens) and probable contamination of the C and/or M printers depending on which ink is next in sequence (M or C).

This web page gets into more of the ink CM sequence issue: Quality In Print: Ink Sequence - 4/C process & beyond - part 2 of 4

This web page post gets into more of the ink CM sequence issue: Quality In Print: Ink Sequence - 4/C process & beyond - part 3 of 4

best, gordon p

 

[tmason]

I love this question.

Prior to G7, we ran everything K,M,C,Y because the purples look much better and
uncoated stocks print cleaner with less mottle. We are short run printer and switch papers all day so this sequence saved us from washing up the press and moving the inks.

Now that we are G7, we print K,C,M,Y and sometimes switch to run K,M,C,Y because of trapping issues in purples. I would like to run this sequence all the time but that would defeat G7 and the proofs match better running K,C,M,Y.

We tried to profile the K,M,C,Y sequence but even with adjusted inks, the color match is still not as close to the proofs. It tends to be heavy on the reds requiring the Magenta density to be run lower.

Some people will tell you to adjust the tack to run the purple colors as C, M but with certain paper surfaces it will still have a mottled look unless you switch the sequence and run M, C.