Ink/Water Balance

[Alex Arriaza]

Sorry im not a native English speaker so for me opaque is the appearance that lacks brightness, i just ask the pressman on the machine why he uses like 40 or 60 even some times he uses 80 percent of water, and the answer was " to make the image look brighter, and keep the impression clean.

[machineguy]

Sounds like you need to re look at everything you do, right down to the type of plates...grained or not....fountain solutions inks, and of course the paper (substrate) you print on.
Hard to help if I dont have all the facts
Martin

[Alex Arriaza]

for example we are currently running:
- Bond 60
- one color, not to many graphs in the paper
- Resista ink
- Fountain solution with glycol with out IPA
- PH 4.3
- F.S 1540u
- 40% water rate
- Almost 0% ink rate

why is the water so high ive seen other presses running full color with couche or texcote with that percentage of water, so why im trying to do is to understand (because i dont quite) the relation between this two factors so i can make better decision next time, ive heard that the optimal way to run its:
- Small amount of water
- Small amount of ink
- Not to much pressure

Try to explain to me if i has the pressman how to make the job, like the steps i have to follow so i can apply it and use that start point to fix the problem or to post what is going on.

[machineguy]

Sounds like you have a fountain solution problem, what happens when you cut the water right back, does the plate scum?
You are very right you should be running minimum pressures, minimum water and ink where you need it.
Martin

[Erik Nikkanen]

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- 40% water rate
- Almost 0% ink rate


- Small amount of water
- Small amount of ink
- Not to much pressure

.

Alex,

The job is has a low coverage % and that is very difficult to control. I have known of pressmen that preferred to run at conditions that were not perfect because of the possibility that if they made a change to the water setting to a better level, they might find themselves chasing the ink feed. Changes in water setting has the biggest affect on the ink feed in normal offset presses.

The terms
- Small amount of water
- Small amount of ink
- Not to much pressure

are terms that pressmen use but these should not be considered as actual conditions in an engineering sense. These terms are used due to the interrelationship of the ink feed and water feed on existing presses.

Break the interrelationship by using a positive ink feed and then what will happen is the ink will be adjusted for the required density and the water will be adjusted for the quality. To keep the plate from scumming or to prevent the ink from getting overloaded with water. With positive ink feed, the water can safely be adjusted to suit the conditions without the worry that the ink feed will be changed.

[George John]

Hi Alex,
Some inks loaded with wax compounds like PTFE and PE to impart better rub and scuff resistance. The more wax compounds in an ink, the less glossy it becomes. Also some inks pick up too much water on press by nature of the resins used in it and more the water, less glossy it becomes. Was the Reflecta ink more glossy than the Resista? It should be. If the body (rheology) of the ink is too soft, it can tend to pick up more water as well. If the ink keys are at Zero, you can change the ink sweep and that will allow you to carry more ink. You are absolutely correct; less is more in Lithography but on light coverage jobs, it could be a challenge. Most inks and fountain solutions are compatible with each other these days and I have seen this fountain solution working fine at other places. But I have seen some fountain solutions that are too aggresive and break the ink down and the ink water balace becomes a nightmare. If you have more questions, please call or post.
George John
269-216-8088

[povertycow]

Run a dry solid with the ink to compare before you blame the water. Many press manufacturers recommened running water between 40-60 %, it gives you more latitude. Roller durometers and settings will affect dampener speeds greatly. Offset stock might increase that number. Don't let the number blur the problem. You can't check emulsion with the dials.

[Alex Arriaza]

I have a question. does any one knows how the ink finds its way to go to the fountain rollers? i see the pressmen always struggling with this issue, they are alway cleaning them because they get dirty so quick, does any one know why this thing happens?

[Alois Senefelder]

Hello Alex,

Google - Sappi.com - on website choose "Central America" area then Tools and resources,

PDFs - Technical Tips, " Inkfeed Back on Dampeners"


Regards, Alois

[Alex Arriaza]

Thanks a lot great info.