milling of offset ink

[kbarz]

kind of embarrassed to ask this question after being a pressman for 40 years, but some of the things we don't talk about in my work place is THE INKS... I know some of the basic's of offset ink, but always want to learn more, could some of fellow lithographers explain why we mill our inks , what benefits it does, and in todays printing world should we or do we.. now my shop does not mill our inks( why ink manufacture says it is not necessary) new ink supplier here and we have encountered some strange things,, having to run some of our controlled pms colors of different shades on units 4 or 3 instead of last down, to make them print smoother. looking at the print with loop, I con see grit in the ink which leads me to think the ink needs to be milled.. what are your feels on this topic.. tks kbarz

 

[Cornishpastythighs]

here is some information you might want to discuss with your ink supplier. You as a customer should not be milling your ink in my opinion (I have never worked at a place that did). that is the job of the manufacturer to supply you with 'press ready' inks. They should have a whole bank of testing equipment and procedures and have good technical support to stand behind their products. Get them in and show them your concerns and see what kind of support you get, that will tell you whether or not they are serious about your business.

Testing Your Ink | Printing Industries of America - Printing.org

ZGR 2020 - 2024 Zehntner-Grindometer - YouTube

 

[Asures]

You should not be concerned about being embarrassed regarding this subject.

The bottom line is that if you are having "Performance Concerns" with the product that you are using, your vendor needs to step up to the table and address the issues. This is where service comes into play. There are plenty of "Order Takers" in the game but few that will actually provide "Technical Support", without question.

Depending on the colors that you have to run on the 3rd and 4th units, you could be looking at a strength and transfer issue as apposed to a bad grind. A bad grind would most likely appear as scratches in the plate or premature image wear of the plates (in particular, light screens).

Hope this helps!

 

[Cold]

Hi kbarz,

As mentioned above, the inks should come to you press ready. The three roll mill is not a piece of equipment suitable for a printer. It disperses the ink at a micron level and is typically the final mixing process done before you, the customer, sees the ink.

The graininess you see in your loop could be "weak mottle". So if the ink you are currently running is weaker and higher tack than what you were used to, it could be printing "nappy" intead of smooth. That nappy look will appear grainy when looked at with a loop.

To test this, pick a pantone color with trans white in it and go to the next stronger color, eg. if you want to print pms 121 then get a can of 122 and print at the density of pms 121. Add a couple of percent of reducer to the can and see if it doesn't print smooth at the lesser ink film. If it does print smooth, then you know what you got and can order the inks accordingly strong and lower tack.

Keep in mind, this is just my 2cp and just a shot in the dark at what your print issues might be.

Best,



Cold

 

[D Ink Man]

kind of embarrassed to ask this question after being a pressman for 40 years, but some of the things we don't talk about in my work place is THE INKS... I know some of the basic's of offset ink, but always want to learn more, could some of fellow lithographers explain why we mill our inks , what benefits it does, and in todays printing world should we or do we.. now my shop does not mill our inks( why ink manufacture says it is not necessary) new ink supplier here and we have encountered some strange things,, having to run some of our controlled pms colors of different shades on units 4 or 3 instead of last down, to make them print smoother. looking at the print with loop, I con see grit in the ink which leads me to think the ink needs to be milled.. what are your feels on this topic.. tks kbarz

The job of milling inks is the responsibility of your ink manufacturer or to the delegation from your ink supplier, who likely has no role in the manufacturing process. There are way too many middle man dealers of ink in the marketplace today who know less about the mechanisms of offset ink than you kbarz. These dealers often sell almost any pressroom supply or consumable you are willing to purchase. My recommendation is to stay away from these type of dealer arrangements and purchase your ink through a legitimate company that manufactures and SERVICES what they sell.

Moving on to the milling of ink and the purposes. Milling, i.e., three roll mills are used to grind the pigment portion of the ink formulation into the vehicle portion. The proper wetting out of the pigment particle is paramount in the production of offset paste ink. Without the proper 'wetting' of the pigment, inks will not develop their potential color strength, their gloss properties and homogenous consistency that are the foundation of a good ink. Further this wetting necessitate is conceived well beforehand of the three roll mil process. Actually, t starts in the lab with experienced formulation technicians that engineer products with the proper drying oils, resins, properly micronized pigments and percentage amounts that allow for excellent wetting throughout the manufacturing process to the point where it resides in your ink fountain is ready for usage. Another critical step is the dispersion process which normally directly precedes the 3 roll milling. Dispersing or high speed mixing at the proper temperature, time and adding techniques is a critical process. When done properly, it actually allows the milling process to be much easier because the pigment is already 80-90% wet out. The roller mill than does the final job that will result in an ink with no larger than 3.5 micron particles which is ideal for offset printing. Beyond this micron size, you can run into a myriad of print and run problems that can impede your print production. One example would be premature wearing of plates, but many other problems, issues could be noted.

kbarz, if you would like me to elaborate on spot colors and address your second question, I will be happy to do so in another reply here. Just don't want to make this too long so you can digest it before the next course.

Hopefully as I go into thesis, Gordo and some others will allow and appreciate my contribution going forward. OK Erik?

Hope this sheds some light on offset ink and the milling, dispersion process. D

 

[Peter Welfare]

And have a look on YouTube for "How Ink is Made"

 

[D Ink Man]

And have a look on YouTube for "How Ink is Made"

It is a very good video Peter, the best.

I hope you are making lots of ink and filling your coffers.

Remember it comes down to TECHNICAL expertise, not putting the $ to the forefront of competitive activity, just because your competition is perhaps mired in this rut.

Words of wisdom to think about. Truly.

D Ink Man