ink/water balance

[ar17]

is there a way to check if printing is overly applied or starving with water? any special control strip i can attach with my color bar? thanks...

 

[gordo]

Ink is designed to take up a certain amount of fountain solution (water).
Too much water - solid ink densities drop, solids become orange peel looking, dot edges or other hard ink/non ink transitions become soft or fuzzy, small areas of ink ma wash away/go blind, trapping is poor
Not enough water - the non-image area of the plate will start to take ink resulting in scumming in the presswork.
Solids and dots in your color bar or live image areas as well as non-printing areas are what you use to check ink/water balance.

It's a bit more complicated since there are 9 different combinations possible:
1 Not enough ink, not enough water
2 Not enough ink, water just right
3 Not enough ink, too much water
4 Ink just right, not enough water
5 Ink just right, water just right
6 Ink just right, too much water
7 Too much ink, too much water
8 Too much ink, water just right
9 Too much ink, not enough water

best, gordo

 

[dana]

fogra had come up with a test form, I originally found this info on heidelbergs website in their "heidelberg news" section

http://www.fogra.org/products-en/download/Extra10web.pdf

-Dana

 

[Lukew]

That test form will only help to show you that all your roller settings are correct..
Your damp feed rate will be dependent on a few things.
1) % coverage of ink on the sheet (more coverage = higher damp feed rate / less coverage = lower damp feed rate)

2) Speed that your running the machine - Faster you run the press the higher the damp feed rate needs to be.

3) Heat in and around the machine will also effect where you need your damp feed rate.

4) Certain PMS colours will need Higher/Lower damp feed rate.

One simple way is to run a certain % screens in certain areas of your colour bar strips.

Check along the lead /tail of the plate there should be a 1mm strip of ink on the plate at the bend of the cyclinder after printing the job, this tells you that you have your fount feed in a good area.

When starting off with a new ink that you havn't used always start off with the minimal fount feed and also ink feed and gradualy bring them up in unison untill both correct density has been achieved and there is a smear free print

Also if you have inked up and find you have had to suddenly raise your damp feeed rate a lot higher, chances are you have put too much ink on, and from then on you will struggle to achive a crisp sharp print without mottled orange peal poor trapping looking print,

Finally your aim should be to print every job with just enough fount to prevent scumming up.

 

[jlind]

There was a test image in the far past made by GATF with the innocuous name of "the QC strip." Don't know if it's around or in a digital form. It was small but let me describe it. There was a solid bar parallel to the cylinder, and then narrow fingers of lines and spaces coming out of the solid at an angle, like 45 degrees. It was important that the lines and spaces were equal width, about 4 mils each. Not enough water, and the fingers would fill in. Too much water and they would look snow-flaked. Probably no place for this target today, but it could be in a color bar.

A star target, the old optical resolution target, could be used in the same way, and this is often on a color bar, maybe the best visual target ever invented for the press operator.

The wise old press operators of the past, probably all laid off by now or retired, would start up the press and cut back the water until there was just visible scumming on the lead edge of the plate. Then the water would be increased by 5%. That should be the running point.

When a plate manufacturer does a press trial for a new product, they establish this low water mark (sic, no pun intended) and then increase the water feed until the density of a target solid density drops 10 points, calling that the wash out point. Sometimes the wash out point never shows up, but the low water point is very distinct.

John Lind
Cranberry Township, PA
724-776-4718

 

[Albert Noel]

The wise old press operators of the past, probably all laid off by now or retired, would start up the press and cut back the water until there was just visible scumming on the lead edge of the plate. Then the water would be increased by 5%. That should be the running point.

this is the method i usually use.

ar17, like said already, if you have good balance the best visual is a small (about 1mm) band of ink at the bend at the gripper edge of the plate that is even all the way across.

 

[Deleted member 16349]

is there a way to check if printing is overly applied or starving with water? any special control strip i can attach with my color bar? thanks...

A method taught by "John Davies" the head printer and trainer at a place where I worked, was used on web presses. It might be also useful on a sheetfed press.

The idea was to take the water feed off and count how long it takes to start to scum the plate. Since there is extra water on the roller train, it takes a short amount of time for that water to be used up and then the plate scums. For that press, I think the target time was about 4 seconds. I don't remember for sure. If the plate scummed up in more than the 4 seconds, then too much water was being applied. If the plate scummed up in less than the 4 seconds, then not enough water was applied.

For your press, when you think the water setting is good, stop the water feed and count until it scums. You might have a count of x seconds. Then see if you can use that method to maintain water setting for other runs by stopping the water feed and seeing if you are more or less than the x seconds. Of course, put the water feed on as soon as scumming starts to avoid waste.

The comment on having a scum line on the leading edge of a plate might be OK for sheetfed presses but it is not good for web presses. One does not want a line on the printed web like that.

I hope this works for you. When I heard of this technique, I thought it was simple and brilliant. And much safer than touching the running rollers with your finger.

 

[Sfdp2300]

Your best bet is when starting a Make ready start out with low water and ink . It is easier to add ink and water than to get ink and water out. Take water out till you scum and then add the water back till the scum cleans up.

The tint line one the lead edge of the plate works well as an indicator. Also if you are picking up the press from another operator and the job is in process of running. Look at all of your plates while running. If your plates look wet and shiny you have to much water. The plates should look dull and flat with no shine in your non image area while you are running.

 

[arfamoe]

The 3 golden rules of offset Lithography
Minimum amount of ink
minimum amount of water
minimum amount of pressure for good ink transfer.
Start water low so that small amount of scum is present, Adjust ink to get to required density, increase water slowly till scum dissapears, add one more click for luck and now you are looking at minimum ink and minimum water.
If you observe scum on one side of the sheet and not the other then look for mechanical issues Rollers/dampners etc.
If you follow the golden rules and still observe Scumming/Tinting look for possible Plate sensitivity issues, ink issues or temperature issues.
Its the mystery of ink and water balance that has long prevented Litho presses from being switched to Auto Pilot
My 0.02c worth

 

[Deleted member 16349]

Its the mystery of ink and water balance that has long prevented Litho presses from being switched to Auto Pilot
My 0.02c worth

It is not a mystery. It is just that the print industry does not want to believe in the explanation that was published over ten years ago. All offset presses do not properly control ink feed. Fix that problem and you will not have the balancing problem between ink and water. Ink will be set independent of water setting.

 

[arfamoe]

Yes but talk to any press operator 10 years ago and getting correct ink/water balance was a finely tuned art learned over many years and shrouded in mystery as to how it was accomplished much like making samurai swords.

 

[Deleted member 16349]

Yes but talk to any press operator 10 years ago and getting correct ink/water balance was a finely tuned art learned over many years and shrouded in mystery as to how it was accomplished much like making samurai swords.

Of course there is a lot of skill required. But what would be helpful is a SITB.
A Samurai Ink Transfer Blade to correct the inherent problem.

It would also cut through the piles of misinformation.

 

[Lukew]

Erik is there anywhere I can find info on this ITB of your's ? I'm just interested in how the concept works..
I can't work out how the ink can be set independent of the water settings..

In my thought's no matter how acurate the ink is transfered onto the rollers,, when ever the ink/fount has to form an emulsion there will always be a direct relationship between the two..
The transfer of ink from the ink duct be it accutate or not is only one part of the many parts that effects the ink/ water balance..

 

[Alois Senefelder]

Fundamentals - Ink - Water Balance

Fundamentals - Ink - Water Balance

Run sufficient dampening fluid to keep non-image areas clean, while trying to form a stable printing ink emulsion(water-in-ink)
A simple visual technique for locating near-optimum balance, using the GATF Star Target or the 70/80% Halftones on the Print Control Strip, watch that enough water is being fed to keep these TONES OPEN, too much water causes ---- "Snowflaky Solids" and "Wash Marks" print defects.

A too dry indicator is seen by checking the "Star Target" radial wedges at the centre for
"Ink Grains or Specks" pattern that begin to appear in the unprinted wedge area where the "Inked Wedges" are the closest to each other.

During the print run visually check the Plate Cyl. as they rotate, the plates should have a "Dull Sheen" look, at a press stop a "Thin Scum Line" on the plate lead bend about
1mm wide - even across is a good "Indicator" of correct Ink-Water Balance.

Regards, Alois

 

[arfamoe]

Yes all good stuff, I knew a web pressman in the UK who just listened to the snap of the blanket and paper to tell whether or not he had the correct ink/water balance, loud snap=too dry no snap=too wet, as i say a timed learned skill.

 

[Deleted member 16349]

Erik is there anywhere I can find info on this ITB of your's ? I'm just interested in how the concept works..
I can't work out how the ink can be set independent of the water settings..

In my thought's no matter how accurate the ink is transfered onto the rollers,, when ever the ink/fount has to form an emulsion there will always be a direct relationship between the two..
The transfer of ink from the ink duct be it accutate or not is only one part of the many parts that effects the ink/ water balance..

Lukew,

The ITB technology has had a US patent # 6,857,366 for a while and now also
has a Canadian patent #2,288,354. You can look up the description at the US patent office. The description is in legal terms required for patents but you should get the idea.

I can understand why you have a problem with this. Part of the reason is in the misunderstanding of what happens now. You might assume that the ink feed now is accurate but this is not true. The ink key might feed ink accurately onto the ink fountain roller but the transfer of ink from the ink fountain roller to the high speed roller train is not at all accurate. You have never experienced accurate ink feed and therefore you have no direct experience. Without direct experience to a positive ink feed system it is difficult for printers to imaging what will happen. This is especially true when there has been decades of bad explanations of what is going on.

It is easy to think of ink emulsification as a factor but it is not. The ink is always emulsified. The process will not work if it is not emulsified. One of the problems with the existing inconsistent ink feed process is that when one increases water, that goes up to the ductor and actually starts to starve the ink feed. Increase water enough and you get wash out. The emulsification becomes lots of water but little ink. With a positive ink feed, you can not wash out the print. Print quality might suffer but only at extreme water setting conditions. The operating window is much larger than you would think.

The ITB is only one way to make the ink feed independent of the water, press temperature or press speed but it is a very low cost way to do it.

The ITB is not a product. My market is press manufacturers. I would not get one penny unless it worked. The biggest obsticle to overcome is changing the way people think about the problem. It is quite an easy problem when looked at from the right direction.

 

[Deleted member 16349]

Yes all good stuff, I knew a web pressman in the UK who just listened to the snap of the blanket and paper to tell whether or not he had the correct ink/water balance, loud snap=too dry no snap=too wet, as i say a timed learned skill.

There are at least two technical papers related to the acoustic analysis of the splitting of the ink film in the roller train related to ink water balance. So some researchers have followed that path of the skilled pressmen.

 

[Alois Senefelder]

What Rubbish !

What Rubbish !

A loud " Snap" equals POOR tension control of the Web - Too much Water results in A WEB Break + and a Blanket Cyl. wrap !!!!!!
Too much Ink also results in --- A WEB Break and a Blanket Cyl wrap !!!

Regards, Alois

 

[arfamoe]

A simple fact

A simple fact

A loud " Snap" equals POOR tension control of the Web - Too much Water results in A WEB Break + and a Blanket Cyl. wrap !!!!!!
Too much Ink also results in --- A WEB Break and a Blanket Cyl wrap !!!

Regards, Alois

Come on now you are citing the extremes of ink/water flooding and starvation which of course would cause blanket wrap up even on sheetfed presses, i guess this pressman knew his press and the sounds it made, very little technology on the press in the old days (early sixties) and running a litho press was not an exact science.Mixing our own fountain solution, ink that varied by the batch, Blanket technology nothing like it is today and offset plates, well they still give me nightmares. The bloke was from your neck of the woods and calling someones else's comments here Rubbish is not very sporting now is it old chap.
Regards Arf

 

[PatQcCa]

Every reply to the original post are single way to resolve ink/water balance.

Each explanation reminds me a problem that has been occured on a press or another one day or another time...

There is no ''one big solution'' it's a receipe between 3 things: goodwill, good running press and good operation...a lack of 1 ingredient or a part of the 3 ingredients may result in many problems.

I really like the way everybody try to explain the problem...great community.

Pat
(sorry for my bad english)