Ink order for 4 colour process...

[Disappointed]

Thanks D,

But surely having a weaker ink will mean I need a thicker film on the job to achieve my target SID value? This would sound like a recipe for set-off etc, I could be exchanging one problem for another? Also as I would be running a thicker film on the plate, my TVI values will be shot to bits and need calibrating to compensate.

Today I have been running coated stock, 14 runs of 1600sheets, all of which I would describe as difficult forms - mostly black text with the odd thumbnail here and there.

I tried opening the outer magenta and yellow duct keys a little and was impressed to find that at the end of the day the yellow ink contamination was far better, pretty much where I would expect it to be, thanks for that tip.

 

[D Ink Man]

It would actually be a more normal film, across the width of the unit. An ink film that resides too long in the ink train is subject to severe bomabardment from the fountain solution and all the other chemistry going on in the offset process.

It is certainly the lesser of the 2 evils, and is a practical short term remedy for the problems of light coverage.

People that practice the daily rigors of lithography understand this, that sometimes you have to deviate from the normal transcript and do what it takes to deliver a quality job for print and ease of runnabilty.

Some do not understand this and that is why you got a 'like' on your last reply. A theorist engineer who was never responsible to put out one piece of sellable lithography.

This is your job, and also extended as my responsibility, for good ink product and service.

That is what I can offer.

Best Regards,

D Ink Man

 

[Deleted member 16349]

It would actually be a more normal film, across the width of the unit. An ink film that resides too long in the ink train is subject to severe bomabardment from the fountain solution and all the other chemistry going on in the offset process.



Best Regards,

D Ink Man

I believe the discussion is about a waterless press.

 

[white rabbit]

The setup - B3 Waterless Offset machine.

Can anyone tell me why I should not alter my ink order from K-C-M-Y to Y-M-C-K??

What are the possible side effects of doing so?

Is there a specific reason for running K-C-M-Y?


Many thanks


Dave

Sees to me the tack of the individual color ink has to be in the correct order as well, for trapping purposes.

 

[D Ink Man]

Actually it is even worse in a waterless situation with the critical temperature windows.

Hang up in the ink train = DEATH.

Comprendo?

Either way, it is still offset printing. It is a chemical process.

Like dat all.

D

 

[jason3791]

In my print operation I would rather not change out the yellow for different strengths depending on the coverage or print area..... Plates on and plates off, and on to the next job. Cleaning out the fountain to change the strength of my process colours seems absurd to me. Doubling the ink film on the sheet (theoretically speaking) would definitely require new plate curves whether the hue was consistent or not. I cannot imagine how we might think that any significant increase in dot gain would not effect our process work in a dramatic way. I feel sorry for the operator that has to match a standard that was created with the stronger ink and calibrated dots, when he is handed a pail of ink cut by 50% with trans white. On a press running water (which is not an issue in the case being discussed) I do believe that more ink typically means more water. More ink and water equals an even heavier film on the forms. Heavier film on the forms which oscillates into the non image area or outside the sheet edge means faster travel up the unit to the ductor, and we all know what this means, especially if those keys are still closed up! If you have an ink tack issue deal with it methodically...... you know what I am talking about.

This could go on forever and I have had these discussions many times in the past. I remember the days of trans white and linseed oil in a bottle, that seemed to solve lots of different problems in the minds of many. The bottles in our shop are gone and the ink stays consistent. So does my dot funny enough.... It is nice to know however that we do not need engineers in the industry, and that all of our problems can simply be solved by our ink "man". I suppose that back in the days of linseed oil and trans white, it was the loudest bully in the shop that knew the most. Some of us seem to be incapable of removing ourselves from that era and chose to slander and ridicule rather than attempt to understand that there is possibly a need for the information an "engineer" can provide. I agree that the information is sometimes not practical, but I cannot think of a reason that one would attempt so lamely to discredit and dismember for no apparent reason...... Give it up.

 

[D Ink Man]

@jason3791,

OK then just add 20% trans white. I can see we're going to have to go slow with you.

D

 

[jason3791]

You might as well keep on driving by...... Nice of you to throw one at me though......

 

[Disappointed]

In my print operation I would rather not change out the yellow for different strengths depending on the coverage or print area..... Plates on and plates off, and on to the next job. Cleaning out the fountain to change the strength of my process colours seems absurd to me. Doubling the ink film on the sheet (theoretically speaking) would definitely require new plate curves whether the hue was consistent or not. I cannot imagine how we might think that any significant increase in dot gain would not effect our process work in a dramatic way.

THAT is how it should, and usually does, work. We have NO chemicals, NO additives, NO reducers, NO tackifiers etc in my shop, these were disposed of long ago. We only use one brand of ink, I only ever run process as well - no pantone, no metallics, no varnishes, I can expend all my effort on producing accurate colour work.

When running a calibrated system, you really cannot add anything at all to the ink, doing so is guaranteed to affect TVI and result in a poor match, yes you may get the job done without contamination but it will not pass muster at the certifying stage.

Moving on, I have had contact from our supplier and the ink manufacturer and they are bringing me a new formulation of inks to test very soon, if these work then i will install them as my standard choice. The yellow is too tacky and the whole set is not duct-fresh at present so they are working to alter the make-up to remedy this. AFIK I am the only user doing this testing on my press in the UK so its quite interesting to see what happens as things are tweaked here and there.

Dave

 

[jason3791]

Excellent! Let us know how you make out. Great discussion. Wishing you well.

 

[RGPW17100]

When running process we are stuck with many jobs that require little ink. In my case it is usually Cyan. What D ink man is saying will work better in these instances due to ink not being replaced in the roller train. If the ink is not going on the sheet you will have all kinds of problems like ink drying in the roller train and the inability to keep the ink constant. Jobs that are paint jobs are easier to print then jobs that require no ink. Your TVI curves are useless in these situations and it is better to reduce ink pigment so you can apply a consistent amount of ink. However with the runs being only 1600 and some may have a lot of ink and some may have none you are better off not doping the ink and trying to print the best job you can with what you have. It is common for the yellow to gray out in the roller train. I have seen this and because yellow is so light it usually does not pose as big a problem hitting a proof as the other three inks. I would stay away from changing the ink sequence. Black should always go down first in my opinion. Usually this color is wet trapped better going down first.

 

[D Ink Man]

@RGPW17100

Explained excellently with intelligence, so the average homosapien can understand. Thank you.

D Ink Man

 

[Disappointed]

When running process we are stuck with many jobs that require little ink. In my case it is usually Cyan. What D ink man is saying will work better in these instances due to ink not being replaced in the roller train. If the ink is not going on the sheet you will have all kinds of problems like ink drying in the roller train and the inability to keep the ink constant. Jobs that are paint jobs are easier to print then jobs that require no ink. Your TVI curves are useless in these situations and it is better to reduce ink pigment so you can apply a consistent amount of ink. However with the runs being only 1600 and some may have a lot of ink and some may have none you are better off not doping the ink and trying to print the best job you can with what you have. It is common for the yellow to gray out in the roller train. I have seen this and because yellow is so light it usually does not pose as big a problem hitting a proof as the other three inks. I would stay away from changing the ink sequence. Black should always go down first in my opinion. Usually this color is wet trapped better going down first.

Great reply, thanks,

this is where we are lucky only being a B3 format user, due to the small sheet size I can set my press to run just the colour bar all day if wanted, and to ISO standard

We can't really disregard the TVI curves most of the time though as even on this fiddly sort of job, the thumbnails represented actual items so the colours were still important.

I am hoping the new ink mix will solve a lot of our problems and the tip with opening the duct keys in non-image areas will fix the rest.

 

[Disappointed]

Well, we are testing the new custom ink mix and so far the resuts seem promising. The colours are an almost perfect match to the ISO standard which is good, there are no signs of toning ether so the temperature range appears correct as well.

I do have a small issue regarding magenta / cyan trapping and we are trying a few things tomorrow to hopefully get this nailed. Currently the magenta is not wet-trapping very well over cyan and as there have also been some minor signs of picking with the magenta, my guess is that the magenta tack level is too high.

I'm going to try varying levels of tack reducer and see what results are gained.

 

[Disappointed]

Tried the tack reducer in the magenta, not so good so we have swapped the laydown order to K-M-C-Y and got a massive boost in C-M trapping which was good but now we have cyan in the yellow duct. This was mostly remedied by adding the tack reducer to the yellow and we now have decent C-Y trapping as well as minimal contamination.

Tomorrow I am cutting the reducer back out and instead increasing the press temperature a few degrees, this should have a similar effect according to the ink guy but without the use of additives.

See what we get....

 

[D Ink Man]

Weaken the yellow by 15%. Will curtail the blue contaimination.

 

[Lukew]

Our process isn't waterless but I assume results would be similar. When we used to run K+E ink it had to be run KMCY, this was the recommended sequence from the ink tech for that ink. If you tried running it KCMY you Cyan/Magenta trapping was horrible.
The issue we found running KMCY with that ink is skin tones didn't look as good, Grey's had a red hue to them and were a lot harder to hit. Comparing the same test forms against other ink sets run in the normal KCMY, you could see that KMCY didn't look as good.

I believe Gordo posted years ago as to the downside of running KMCY.

 

[Disappointed]

Thanks LukeW

there is a colour shift but so far it's been acceptable, we don't print many skin-tones as our work is mainly studio designed stuff, very few real-life pictures.

I guess this is one of the stumbling blocks of waterless - very poor support from the ink manufacturers, the major waterless ink is Toyo but is not ISO in any way and has a very cold look to the print, very hard to make it look warm no matter what you try.

The last one we had which was from Stehlin-Hostag was perfect for almost three years, we were in waterless nirvana until one day it stopped working once the press warmed up. This was either due to an ink formulation or plate change, neither one could we get a reliable answer on so we had to ditch the ink as there are no other plates.

That leaves us with just one other ink which we are trying now, but at least we seem to have the manufacturers on our side as we are the only people anywhere to be testing this mix which is kind of interesting in a sadistic way Hopefully it will prove worthwhile and we can get a reliable ink-set again with more technical backup for the future.

 

[Prepper]

If you have room on your sheet add a take off bar across it, as large or as small as you can fit. That pulls some ink and helps smooth out our low-coverage areas.

 

[Disappointed]

Thanks Prepper, we used to do that many moons ago, unfortunately nOt enough real estate on the sheet now.

Today I upped the press temperature to 23c and stopped using any additives, theory was that the increase in temp would also lower the tack level, the theory it seems was sound.

Managed a whole day with minimal contamination and also pushed the boundaries by running almost flat out all afternoon, this gets the press temperatures up to maximum and would usually resut in some toning on the old inks, even at the higher temps this ink held clean.

I will have to do some minor recalibration due to the increase in temperature causing an expected increase in dot gains, but I am fairly confident this formulation is pretty good.

We also printed some 'real' images and skin tones etc appear unaffected and easily correctable by running the yellow at the upper end of the tolerance range, this also gave better yellow/cyan trapping values. The trapping I am getting now are probably the highest values I have ever seen on this press, all 90-95% which I think is pretty good?

Good to have a positive outlook at last.