variation

minch

Well-known member
Hi, first may I point out that I am a prepress guy and not a pressman and therefore this question may be stupid - please forgive my ignorance.

THE PROBLEM: many of the single Pantone colour print jobs we are outsourcing arrive back with a variation in colour across the entire print run. It is not a linear variation e.g. getting lighter as the run progresses. It is just random. When our client puts a spread of these items out on a table for people to take one then the variation in colour is off putting - even though it is only a small, but visually significant amount.

Example 1: business card, coated 300gsm, 2 Pantone colours on face which are fine, 1 Pantone colour on rear which is full coverage of business card with one piece of reversed out text of a website address. Run lengths: 250, 500, 1000 & 2000.

Example 2: postcards, 300 gsm stock, full coverage of 1 Pantone colour to face with reversed out type saying, "Summer Event Special" the reverse has two colours and is fine. Run lengths: 1k, 2k, 3k, 4k & 5k.

It appears to only be a problem when the entire area of the job is being coated with ink.

The business cards are not gloss varnish coated, but the postcards are.

Is this normal? How can we get rid of it?
 

gordo

Well-known member
The variation through the run is normal. Due to the short run length the press does not have time to reach ink/water and density stability.
The variation is likely also happening in the small areas of color but is just not as visible.

The solutions would be to increase run length, increase wastage, or run on an inkjet press.

best, gordo
 

Cornishpastythighs

Well-known member
Colour variation through a run is normal in Lithographic printing. Excessive variation however is not normal or acceptable.
As you are not the actual printer it is difficult for you to solve the printers colour control issues. You could of course try another printer and see if they do better but unless the printer has his process under control you will get the same result. I would be inclined to watch one of your press runs and see if you can spot anything that could be contributing to the excessive variation (Operator over control for instance) Maybe Digital is the way to go.
Good luck
 

saso777

Active member
It is normal to have variation on offset lithographic printing especially when you do short runs. There are variation also when yo do long runs who of course must not be out of standard's. Maybe for short runs you should tray digital printing.
 

Fii

Member
Short run, not equaly adjusted ink zones over the press sheet and postpress workers whoose mixed up your cards like playing cards before game, hoping this way client wont see colour variaton.
 

Lukew

Well-known member
With todays ever decreasing allowable overs per job, it is getting harder and harder to get a stable print especially on pms colours where by cip profiles have limited use.

We are a short run shop, some PMS jobs are down to 20 sheet runs if its business cards others up to 2000 for letter heads etc. we are allocated 50 sheets to get fit & colour.
This is where the problem starts, you can't get a stable ink water balance & the correct colour in 50 sheets ! So at times the battle continues into the run trying to stable it out..
It goes completely against my values, and I don't think sellable sheets should start until ink water balance & correct colour is achieved.
 

Cornishpastythighs

Well-known member
Just a quick question, who is going to be asked to pay for the extra sheets needed to get the press to 'stable' condition. On some old presses that maybe have'nt had the best maintenance etc it could take many hundreds of sheets to reach stable ink/water balance who will absorb this cost I doubt it would be the customer.
Just a question
 

Fii

Member
Are those b-cards in price of gold or platinum then ?

ok, its no problem to get colour right in less cost. if paper calipper is the same its likely to use already used paper for makeready. But enyway, set of plates for 20 sheets its awfully costly!
 

minch

Well-known member
The variation through the run is normal. Due to the short run length the press does not have time to reach ink/water and density stability.
The variation is likely also happening in the small areas of color but is just not as visible.

The solutions would be to increase run length, increase wastage, or run on an inkjet press.

best, gordo

Thankyou everyone for all your help - armed with this information I can now go back to the printer and renegotiate a higher cost price to include the required sheets to get a better ink balance on the job.

One last question: does it matter if the press is alcohol or non-alcohol? Will both types of press be capable of getting the ink balance required?
 

gordo

Well-known member
One last question: does it matter if the press is alcohol or non-alcohol? Will both types of press be capable of getting the ink balance required?
Yes.
But realize that offset presses can be stable - but not consistent. There will always be variation in the run. But when the press is printing in a stable condition that variation will be much reduced.

best, gordo
 

Erik Nikkanen

Well-known member
Yes.
But realize that offset presses can be stable - but not consistent. There will always be variation in the run. But when the press is printing in a stable condition that variation will be much reduced.

best, gordo
I pains me to hear some things but I will not go into the engineering view on stability, consistency etc. For the general audience the comments are OK. Ouch :)

Yes, there is variation. There is variation in everything, but that is not the issue with respect to offset printing. What is important is the level of variation. If the variation is so small that it is basically not noticed as a problem, one would not be discussing it. When the variation becomes large enough that it causes a problem, then one would hope to do some things to reduce it.

There is no level of variation in offset that is inherent to the process. The level of variation is usually due to the design of the equipment, environment and materials used in the process. There is always a reason for variation and if one knows what it is, then one has the potential of reducing it or even eliminating it so that it is at a level that is a non problem.

Process improvement is about eliminating the causes of variation and one should always be looking for causes. Never accept the condition where variation is a problem as being normal.
 
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kbarz

Active member
alcohol is very offset press freindly, but we here in u.s.a in larger shops must use alcohol subs which makes printing harder to control.. both types will work ,,alcohol the better of the two.. i have been alcohol free for20 plus years,so i find it to be just another day at the shop.. and both will balance out, and this is where the craftmanship of the press operator comes into play,knowing your press,inks,paper,rollor settings,water temps,ink rollor temps,running as fast as the job will let you, this and much more all comes into play very quickly to get that ink/water balance. i have 3-4 make readys a day/ 4/cp+2cc 600 sheet runs 24 up on sheet 26.50- 37.00. and we got to hold that color very very close, no more than 3-5 points on xrite hand held... kbarz
 

Alois Senefelder

Well-known member
Variations and Erik !

Variations and Erik !

Hello Erik,

In the interests of raising awareness of variations in Lithographic Printing, please give us your

estimate of input variables of printing Black Ink on Coated Paper on a single colour sheet-fed offset press,

then give us a figure for the secondary output variables, next the tertiary output variables.



Regards, Alois
 

Erik Nikkanen

Well-known member
Hello Erik,

In the interests of raising awareness of variations in Lithographic Printing, please give us your

estimate of input variables of printing Black Ink on Coated Paper on a single colour sheet-fed offset press,

then give us a figure for the secondary output variables, next the tertiary output variables.



Regards, Alois
Why? Alois, you are not going to believe what I say anyways.

The testing of my technology on a packaging press here in Canada will hopefully answer the main question for those who can't believe the explanations I have been giving for years.

My main hope is to get the press manufacturers interested. If that is successful, the printers will eventually follow as usual once they can see how it works.
 

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