Ink density - anilox or formula impact?

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Ink density - anilox or formula impact?

Postby barb » Mon Sep 25, 2017 4:28 pm

Sorry guys but I need your help again, I can't seem to find any useful literature on this subject and our ink supplier is not much of a help on this matter...

The problem is - our ink densities are mostly lower than they should be, especially black - at most time and speed we have about 0,9-1 density.
Viscosities are monitored through the machines automatic system and for all four process colors are kept around 20.

As a prepress operator I've been shouting that our black is way too weak, and at most time more gray than black but each time I would get an answer that we can't get it stronger because we have too fine aniloxes for cmyk jobs but I just can't accept that answer and I think no one until now has taken the time and will to figure it out.

Aniloxes are 450 l/cm, 4,5 cm3/m2 and our ink formulation is for example: 50% base black, 25% technical varnish for lamination, 10% base varnish and 15% alcohol.

Since I really don't have any knowledge on what precisely those components do I'm stuck on messing with formulations. I tried one blind test with 60% base black 15% technical 15% base and 10% alcohol but got the same result. Then we added about 2 deciliters of methoxy (that one that 'slows' the ink) into 15kg of ink and I measured 1,30 density but right after the second stop and run it dropped again to 1,05.

I also tried googling some info on ink formulation but most of it is for water based, ours is solvent based.


I know this is to much to ask but I really can't seem to find any help around me and I'd appreciate any of your advices.
barb
 
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Re: Ink density - anilox or formula impact?

Postby Gory » Tue Sep 26, 2017 10:01 am

OK, I'm guessing reverse print for lamination - do you use a backing white? are you checking densities off press? or after lamination? or after 'faux' lamination?
Anilox volumes look reasonable.
The way you measure densities greatly affects the values you get, and should be aiming for, on clear film, with no white ink, un-laminated, over a white tile, numbers will be significantly lower than laminated or backed with white ink (Black density of 1.1 would be reasonable using this method) - same is true for any blended colors, they are going to look much different after lamination.
You quote a viscosity, but we need to know what method you are using? (Zahn 2, Zahn 3, Shell cup...)
Not knowing your ink system (other than it is solvent) I can only guess any further.
First off get the 'blend ratio' recommendation from your ink manufacturer - that would be how much base (base black and base varnish in your stated example) to how much technical varnish they recommend (60:40, 70:30, whatever) the alcohol (is it just alcohol, or a blend?) is just there to achieve viscosity, doesn't impart any properties to the ink as such, other than making it thinner and altering the drying speed in the case of blends.
Best guess is leave out the base varnish and proportionally increase the black base (but maintain your 65:25 ratio, rounding up that's approx. 70% base and 30% tech. varnish, then add solvent to achieve viscosity)
As far as what the components do, your 'base' imparts the color (in the case of base varnish, this would be used to reduce color strength) and your 'technical varnish' imparts the properties you need (makes it stick to the substrate, allows lamination bonds...) that is why maintaining a recommended base: tech varnish ratio is critical, and why I would hope your blind test with a base to tech varnish ratio of approximately 83:17 was not in production, chances are properties were adversely affected if this is outside of your ink manufacturers recommended ratio.
Gory
 
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Re: Ink density - anilox or formula impact?

Postby barb » Tue Sep 26, 2017 12:50 pm

I can't thank you how much I appreciate this explanations, this really helps me to understand the whole system better...

Yes, reverse for lamination - forgot to mention it. Not sure what 'off press' means but operator starts the run for the job, cuts a sample and we mesaure the densities with spectrophotometer.

The test mentioned in my post was measured on film with toned white underneath so that 1,05 we got at the end was still too low/too gray.
I understand the variation between clear, with white and after lamination, but since most of our jobs require backing white, my goal is to set the formula so I get about 1,30 ink density for the black on film with toned background white. Then I can run a couple of meters without the white, measure it and next time if a job comes up that doesn't have white underneath - the operator still knows if the densities are close to what we want to achieve.
After we solve all this issues at the beginning of the print process I will deal with measuring the differences before and after lamination.

Viscosity is measured with Din #4 cup.

The only thing my previous coworker managed to find out from our ink supplier is that they reccommend 25% technical varnish, nothing else, but I will give it a try myself and contact them to see if I can find out anything else useful.
As for the base varnish, forgot to mentioned that I was told that we use 'base varnish slow' for process ink and 'base varnish fast' for spot inks? Doesn't make much sense to me at the moment, but nevertheless first I'd go for a 65-70% base black, 25% technical varnish and add 5-10% base varnish if needed. Alcohol is I think about 90-95% and the rest is acetate.

Our boss insists that our formula MUST have alcohol in it, but I'm thinking, if the machine already has it's automated system for maintaing the viscosity, then the alcohol isn't necessary in the formula itself and we can have much greater control and possibilities in messing with the formulation?

PS. my blind test was not in the production, it was just a quick random test to see if 'anything' will happen, but we replaced it exactly because we didn't want to risk isuses with the rest of the production process. We also today found out adding the methoxy wasn't the best idea (also caused lamination issues but fortunately at small cost).
barb
 
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Re: Ink density - anilox or formula impact?

Postby Gory » Tue Sep 26, 2017 1:16 pm

Ok, so max strength you will be 75% black base, 25% technical varnish, then add solvent to print visc.
Fast and slow base varnishes, if I had to guess (which I do) will refer to their drying rates, slower drying tends to run cleaner for process and screen. Having said that, the % solvent in these will not shift drying rate of ink too far (at least I would not think so, 10% varnish in your ink, maybe equates to 5% solvent in the ink, then you chuck 25% or so more solvent at it to reduce to press viscosity)
Do you have fast and slow technical varnishes? If so, use the fast for line and the slow for process/ screen, if not try running it without the slow varnish, see if it runs clean, it certainly ought to increase your densities as you have 10% less 'clear stuff' in there.
Your point on not adding reducers (for this is what I will call what you refer to as Alcohol, being that it is a blend of alcohol and acetate) is kind of redundant, if you don't mind me saying. The reason being that it is needed to reduce your inks to print viscosity, and whether you add in the ink room, or the viscometers add on press the end result will be that the ink has the same amount of reducers added to it, to achieve the same viscosity, and therefore there are no gains in density to be had.
DIN #4 cup, maybe someone else can chip in I've not used one in forever - more used to solvent flexo in the 25" to 30" EZ zahn 2, and I do not know how they correlate.
next to last thing, and this isn't ink, but what are the condition of your process aniloxes? how long since they were engraved, how many running hours on them. Most shops leave them in the same decks for a long time, until they become damaged are just too worn to achieve densities. Do you have a way to evaluate them on-site? can your anilox vendor help you to do so? do they all put down the same amount of ink? (hint, if you can get the press time, put black in all process decks and draw down individually - do you get the same density from each deck? if you do, this suggests they are all in the same condition, if not, figure out which is best and reserve it for the color you have the most issues achieving density, and use your worst for, probably, cyan - of the process set that is typically the one with the most varnish in it.
Last thing, you refer to a toned white, could you elaborate? is it white, or white with a color added?
Gory
 
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Re: Ink density - anilox or formula impact?

Postby barb » Tue Sep 26, 2017 3:39 pm

Nope, in terms of 'technical varnish' we have them only as 'TV' that is used for 'outside' print, and 'TV lam' that is used for reverse print for lamination.

Yes, the plan is to go for a max possible strength first and from then on we'll see what to do with the base varnish/drying part - if necessary.
It think I get the background of these base varnishes but it's hard for me to fully understand it's behaviour until I test it out on a press (hopefully, all of these tests will happen on Monday and I'll have much more knowledge for further research).

Thank you for the clarification on the 'reducer', that was a general thought of mine but wasn't sure if there's any difference as you say at what time and place is it added to the ink.

We get these cups from our ink supplier so don't have much to say on this subject, but it would be great if someone could compare this to other systems. Lots of stuff we have as guidance wasn't even checked or tested but only stuck with it because 'someone once told us so'. That's also a thing I'm not so sure about, someone years ago told that would be best to keep all visc levels at 20, and no one didn't ever thought about getting them lower or higher to test the result.

I must admit I have no idea how many hours/meters have they ran so far, all I know for now is that we have them as long as the machine - about two and a half years. Just recently I found out our operators don't clean or maintain them as they should so they might as well be damaged/worn. Great idea for the testing - goes on a list for a backup test.

Sorry for some of my expressions, not sure sometimes what's the proper translation. We use the term 'toned white' when we use a sleeve to 'tone' it on the film compared to when using a plate to print it. So yes - it's a clean white ink.
barb
 
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Re: Ink density - anilox or formula impact?

Postby Gory » Wed Sep 27, 2017 7:15 am

Nothing wrong with the DIN cup, I just couldn't remember the values it gave. I found an online conversion table for viscosity cups, it suggests 20 in a DIN 4 is about 25" in an EZ 2, so your visc is reasonable, but you could probably run a little thicker and squeeze a bit more strength, try 22" in a DIN 4, no higher than 24" DIN 4.
Not knowing your operation, nor the hours the press runs, nor a number more variables that can challenge us in flexography, I can't say whether two and a half years is excessive for your aniloxes (assuming the press was purchased new, not with old or used aniloxes) - but it sounds like a long time, do you have any new ones where you could just do an anilox swap on one deck (process black?) and measure the differences in density?
Gory
 
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Re: Ink density - anilox or formula impact?

Postby barb » Wed Sep 27, 2017 1:36 pm

Will give it a go.

Yes it was a new machine, but since it has a software that monitors most of the stuff I'll try to check if there's any data on run usage.
I don't have any extra to do a swap, but the test with the same color on all four of them as you advised is not bad for checking if there are any major differences.

Thank you again for your advices, I think I have enough now for a start and the to-do list is ready for Monday testing. I'll get back to this with the results!
barb
 
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Re: Ink density - anilox or formula impact?

Postby barb » Tue Oct 03, 2017 2:49 pm

Back on topic!

Testing is on-going so I have a question before I finalize my part on ink formulas.

Previous formula was: base ink+tech.varnish lamination+base varnish+reducer(alcohol/acetate).

Base varnish ingredients: methoxy propanol, ethoxy propanol, nitrocellulose, ethanol.

Recent formula: base ink+tech.varnish lam+methoxy propanol+reducer(alcohol/acetate).


From what I understand so far, methoxy and ethoxy propanol are basically same thing (retarders) so we decided to use methoxy as separate component. Now my concern is about nitrocellulose - I already have it as a ingredient in my base ink - but since there was a small percent in base varnish we used previously - do I still have to add it separately in my formula?

Base Black 58%
Tech. varnish 23%
Methoxy propanol 2%
Reducer 17%

gave us viscosity of 23 (DIN #4) and density 1,34 on 450 l/cm, 4,5 cm3/m2, at 250m/min speed. It was measured with white backing, over a white tile.

Gory - your advice on testing the aniloxes with same color worked perfectly. We found out the one we use for black was transferring the ink too weak so we replaced it with another one and the density jumped up from 1,15 to 1,34!
barb
 
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Re: Ink density - anilox or formula impact?

Postby guy de cafmeyer » Wed Oct 04, 2017 1:42 am

I would have the aniloxes cleaned ( professionally ) with ultrasonics or whatever is available ... ie. not just a brush on-site .
Then an anilox supplier closest to you can come in to give you the anilox spec wrt measured volume .
If the spec remains at your suggested volume , then it is without doubt an ink problem .
Locally our printers are mostly using 475's , volume of 4,6 . That suggests to me that your spec is fine , but is it still accurate .?
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Re: Ink density - anilox or formula impact?

Postby Gory » Wed Oct 04, 2017 6:57 am

Barb,
glad to be of assistance, but I think you have more room to increase your black density. The formula you give is excessive on the tech varnish, your vendor said 75:25, you are running 58:23 base: varnish (72:28, not much more to be had, but a little).
Don't concern yourself with the Nitrocellulase in the base varnish, it is a resin, but it should also be in your base colors, so you are not actually 'losing' any NC, just gaining strength by removing the base varnish (think of it as a transparent base color).
you are correct in that both Methoxy and Ethoxy are both retarders, but they have different evaporation rates, so do not consider them interchangeable. I would not recommend summarily adding either, rather leave them out and add a small amount at a time press side if they are needed (you can tell if they are if your print becomes dirty too quickly) record how much (if any) you add press side, and use that as a baseline for process. The reason not to add unless needed is that they are so slow they can be a cause of offset within a printed roll, and - more often - affect lamination bonds/ cause tunneling.
Gory
 
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Re: Ink density - anilox or formula impact?

Postby barb » Wed Oct 04, 2017 11:49 am

cufmeyer - thanks, we'll do some further testing tomorrow regarding aniloxes, and if needed - we'll call our supplier to come take a look.

gory - I might have somewhere incorrectly stated but, our vendor only said they reccommend 25% TV regarding the whole formula (base, varnish and reducer). But I see that as a problem so next week they'll probably come over and I'll insist they tell me what ratio towards the base they reccomend so I can apply your advice correctly.
Right now we have a 58:23 in black that gives 1,34, and 60:25 in magenta that gives 1,1 under same circumstances, so now I can only do a turn over to 65:20 on magenta and see if there's an improvement - if not, I'll wait for them to come and give their specification. I'm a bit afraid to lower the TV down any more than 20 because I don't know if it'll also cause problems on lamination part.
You are correct about the methoxy. So far we only add it to the black ink and we'll see in next couple of days how it behaves after lamination.

I'm actually satisfied on how well is this turning out, I've learned so much in the past few days and the only thing that's sometimes causing an issue is the drying part, but I'll do the research on my own first before I start bugging you guys again :smile:
barb
 
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Re: Ink density - anilox or formula impact?

Postby barb » Wed Oct 11, 2017 1:54 pm

Hi guys, just a small update on my issue here...

Aniloxes were thouroughly tested and turned out fine, no major differences in densities with same ink.
The one we used for black that turned out 'weaker' will be inspected together with anilox supplier (difference between old one and new one was 0,15 in density - tested under same condition)

Our ink supplier answered on my question and their recommended formula for 'max strength' is 65% base + 25% technical varnish + 5% base varnish + 5% reducer which is not far from what we tested so in conclusion - there has to be something wrong with the base ink/concentrate itself or some other components we use.
Why I'm even more sure about that theory is because I found out some documented analysis from few years ago that with same ink, with formula containing around 40% base ink gave out densities around 1,70!

Even though it was very useful for me and the whole team to test and learn about all those chemical reactions and component ratios I will still try and force our ink supplier to get their technicians over here and solve this to the end.
barb
 
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Re: Ink density - anilox or formula impact?

Postby Gory » Fri Oct 13, 2017 1:29 pm

hi again Barb, looks like you have discovered a lot.
If your Anilox supplier are coming to evaluate the (previously) black cylinder, make use of the visit to have them evaluate all of your other aniloxes, then you know what you have.
Aniloxes do wear, variably according to use. If you question this, consider the doctor blades - they are made (typically) of metal and wear due to the friction against the anilox (amongst other reasons), logically they must also cause some wear to the aniloxes. Another way to think of it is if metal rubbing on metal did not cause wear, there would be no need for bearings and bushings.
How long an anilox is serviceable for is an impossible question to answer - it depends on many, many things (blade material, anilox circumference, press speed, run time, cleaning method....) I think you mentioned your aniloxes were two years old. If you only run 8 hours a day, 5 days a week they will still be worn, which reduces the volume of the cells, therefore how much ink they can carry and transfer, thereby affecting color strength/ density. I have visited accounts that wore out aniloxes in 6 months, running 24/7 (if we assume 15 to 20% lower volume than spec is too heavily worn to provide practical service)
Full disclosure - I am an ink guy, but as I am unaware who your vendor is I am most likely not affiliated with them. Although there may be some ink companies that reduce pigment volume to reduce costs, it is not a common practice, and one I have not seen, certainly to the extent your density drops suggest. I greatly suspect your aniloxes are near to or beyond their serviceable limits.
Gory
 
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Re: Ink density - anilox or formula impact?

Postby barb » Mon Oct 16, 2017 12:39 pm

Yup. I'll make sure they check them all thouroughly.

As for the inks - I don't know what to say anymore, I've heard both sides that there's no 'standard' practice to mess with base components but also that some suppliers take our market for granted and basically just send us 'crap' materials. We were until now also the perfect client for that because we had no quality control or checkup for input components whatsoever.
I don't know what's the practice around the world, but ours never gave us some documentation on viscosity of ordered bases nor did we have any detailed specification on ingredients.
I mean, if their 'standard' data sheet says the bases can have for instance 10-50% of ethoxypropanol how in the hell can I know later on why is our ink too fast drying on the press if can't tell if there's 10% or 50% retarder in the bases. That's actually what's bugging me the most. In this moment I have absolutely no clue on how much retarder there is in our base components that is, how much more can I add press-side if needed and not risk lamination issues, or how much more acetate can add to achieve resolubility and not risk 354636 other problems.
I don't know, for now I tend to belive that the inks or the ratios in components are the problem, just based on everything I read and tested so far on both of the machines we have.

Nevertheless, we'll know much more and I'll get back to you when both of our suppliers come in - for the inks and the aniloxes.

One other thing is right now at my mind if you maybe can help - I did some research and found out Sun Chemicals PDF which says that most of the inks for high-speed presses are now propanol based to slow down the drying.
- Does that mean if I change ethanol with propanol I might later have to add smaller amounts of retarder? (just checking, before I start mixing stuff again :smile: )
barb
 
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Re: Ink density - anilox or formula impact?

Postby Gory » Mon Oct 16, 2017 1:26 pm

Hi Barb, the components on the SDS are so broadly listed more as a way to prevent others (customers, other ink companys) from knowing exactly what is in the ink, and with good cause - if it listed everything by a specific percentage, one of their competitors could replicate it and sell it cheaper (they would be able to bypass any research and development)
I have worked in and with ink labs of the 4 major ink manufacturers for over 20 years, it is not common for them to just send crap, especially not to a lamination plant (maybe to corrugated, but lamination no) after all they do have a reputation to protect, and if they sell you crap you could just invite their competitors to trial and move your business to them.
Ethanol and propanol are both alcohols with similar properties as far as resin solution, but different evaporation rates. Propanol is very common in warmer climates, ethanol was common in colder climates, especially during the winter months. If you are already using a retarder to slow your drying speed, then switching to Ethanol would require the use of more retarder, which nobody I know would recommend, it can lead to increased retained solvents, which are your enemy as far as lamination bonds.
Gory
 
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