[theory] What makes white ink so hard to print?

[Screened Gear]

What do ppl think is making the white ink so difficult to print with?
Pigment load and the amount of time it takes to work up the ink

What does it take to make it print better?
Ink needs to be printed about 50 to 100 times to get the viscosity and temperature of the ink correct to have the right flow characteristic. You can use fixes for this like S-mesh, higher tension, lower mesh counts, reducer and even more pressure. What is the ideal way to print a white ink? It should print like every other color.

What are the parameters that need to be controlled in order to get the best print?
Ink needs to be worked up by printing or mixing. There is a point when ink will stabilize. At that point you have an ink that can print for hours at the same setting giving you the same results. When I print I am doing slight adjustments to the press on high end designs to keep the same coverage and opacity until about 100 prints. At that point the ink is stabilized and I am printing as soft as I can and still clearing the screens.

How much are we falling short of what the inks can really deliver by either not following the manufacturer's recommendations or not putting in the time to figure
Manufacturer make ink. They only state safe performance and use of the product guide lines. This way they don't get sued. It is our job to figure out how to use the product the best way. You don't ask ford to tell you how to win a race. Race teams push the cars way past what the manufactures think is possible.

how to print better? Is the difference in results negligible or is it significant?
The real question is why? Why do you need to get better? Are your clients asking for better? Will you get more money for this high level of printing? What is your goal? I personally think going after the unreachable is a waist of time and money if it does not have a equal pay off.

[blue moon]

many, many good points and a lot of it points in the right direction, so keep them coming!

As far as why do this, we did a little bit of testing and have figured out how to print the white ink at 4 times the speed we used to do with significantly better opacity and deposit control. So there will be a savings in the amount of ink used, increase in productivity by printing faster (and using less ink while at it), being able to deposit in one stroke what we needed two swipes for (equals even more production speed) and in many cases not needing the highlight white any more. Let me put down one real number here. Our max speed printing on top of an underbase was 450-500 shirts per hour (full front). In most cases we were at low 400's per hour. Right now we can run those at almost 900 per hour. That is a significant increase in production capability! So that's one of the reasons. . .

pierre

[starchild]

If 50 - 100 prints are required to get the ink moving then that's a color shift in that many shirts compared to the remainder of the shirts in the run. In this case, the ink's Yield Stress (measured in dynes/cm) is high.. So a bodied ink, with a low yield stress value, that is just sitting in the mesh, will immediately become fluid by a gentle push by the squeegee blade. The low yield stress value tells you that the ink will flow with minimum squeegee angle, pressure and speed..

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[blue moon]

oh oh..... I need a lot more time to respond to that question Pierre.

Let's start with printing the ink at optimal temperatures.  Remember all lab testing is done with the ink at 72-75 degrees.  Also, right from the mixer.  A retain is kept from every batch for at least a year.  All ink will body up over time but it usually will follow a curve reaching max body within a few days to a few weeks.  But the labs only test the retain if someone has a complaint about the ink.  Of course long term testing is always done when a new ink is created.

So, one big issue is trying to print white ink is: Printing when it is not at optimal printing temperatures.

There are more and I will try to get to them later.

Good post to follow!

how many  of you out there print with ink at 72-72 degrees? White ink especially! (think hot/cold weather, hot platens while flashing)

pierre

[blue moon]

The only issues I have with white plastisol:

1. Gumming up and climbing the squeegee, even on the creamiest inks, more than any other color.
2. The way it reacts to static electricity and flings off little strings that pull away from the mesh.

The actual printing is pretty straightforward with the right variables.

why is it climbing? do we need the feature that causes it to do that? would you (everybody here, not just mimo) sacrifice printability for less climb, or would you rather there was a lot more to clean up but it printed better?

pierre

[blue moon]

1: Lack of understanding/control of variables. 
2. Understanding and controlling ALL the variables which seriously impact labor and materials costs.
3. What's the most important variable when printing white ink?  The same as any other ink--all of them.
4: I'd rephrase--how much are we falling short of what inks can deliver by not understanding and controlling the variables?
That depends--on what variables you understand and control.  Tough to know what you don't know you don't know, however.

this has to be one of my favorite post in a very long time, thank you!

so what are the variables that we can control?
so what are some of the things that are preset in the ink and we have no control of?

again, these are questions for everybody, not just SF!

pierre

[blue moon]

I'm not sure about counting on the information and  suggestions of the suppliers/tecnical support/manufacturers as they have no knowledge of the specifications of the tools used in your operations.

we actually talked to the lab ppl, so yes, we dug deep!

What the ink manufacturers should be providing the printers is the Inks analysis data.. These test are done and then technical support sells the ink as- awsome, creamy, good coverage, nice hand, low flash and a bunch of other adjectives and platitudes..

An ink should be selected based on our constructed pump's ability or our pump should be constructed to match the inks personality.. In any case it must be orchestrated..

printficient just called me with a similar comment just few days ago! So I am reading this as, "Damn it, give us some data so we can buy the right pump!!!"

To understand the personality of the ink we need to Know it's properties:

Optical Sepcifications-
L, a, B
Delta E
Peak Spectral
Gloss percentage
Opacity Per Mil
Bleed Resist
xy Chromaticity Coordinates

Rheological Specifications-
Relative Viscosity
Yield Stress
Plastic Viscosity
Shortness Ratio
Thixotropic Index
Tack Percent
Servers Viscosity

Thermal Specifications-
Low Viscosity
Gel Point
Fusion
Remelt
Hot Tack (after flash)

Physical Properties-
Grind
Emissivity
Specific Gravity
Surface Tension
Critical Surface Tension
Percent Plasticizer
Shore A

I have to admit, I only made it two lines in before I had to start googling stuff. Definitely gets me thinking on what we are to measure and why, thank you!

Having this relatively short list of properties made available and technical support (job should be) making sure that printers understand what effect each spec have on the ink, then printers will not have a problem choosing the right ink to match their unique setup.

don't see it coming from the ink manufacturers as many of them do not know what the actual measurements are for most of those numbers!!!!!!!!!!!!

pierre

[blue moon]

Great points to understand if you are an ink chemist but will not necessarily make you a better printer.

you are right, the press operator does not need to know this, he/she can be told how to set up the press. The decision maker (production manager or owner operator) should understand as much of this as possible if they want to make their lief easier.

pierre

[ScreenPrinter123]

Joe Clarke you're needed at the front desk. Paging Joe Clarke - front desk.

[Homer]

Dr. Pierre, do have any findings you are willing to share? what has changed where you can print 4x the speed?

[blue moon]

Dr. Pierre, do have any findings you are willing to share? what has changed where you can print 4x the speed?

we changed the mesh to the 150/48 (LX in this case but regular S should work just as well) and stood up the blades. With a little bit of tweaking, we got it to work. But wile this might be the final result, or something approximating one, reality is we just made our ink work in our shop by using something more appropriate to it.

The point here is that if we measure the inks performance, we can KNOW rather than guess what are the correct parameters and tools we need to use.

pierre

[mimosatexas]

The only issues I have with white plastisol:

1. Gumming up and climbing the squeegee, even on the creamiest inks, more than any other color.
2. The way it reacts to static electricity and flings off little strings that pull away from the mesh.

The actual printing is pretty straightforward with the right variables.

why is it climbing? do we need the feature that causes it to do that? would you (everybody here, not just mimo) sacrifice printability for less climb, or would you rather there was a lot more to clean up but it printed better?

pierre

I could give a crap about the cleanup in this regard, and am more concerned with consistency.  I am probably more concerned with ink that performs consistently over time as I print on a manual and have plenty of other variables to account for on each stroke without worrying about adjusting over time for changing ink characteristics.  My main concern is the ink losing viscosity over time instead of gaining it.  My experience is likely different from most as I am printing on a manual, but I am still preheating metal platens and pre-mixing, etc.  White ink when properly prepared prints like butter for a while, but tenses up over time, causing it to ride up the squeegee.  It clears worse, and loses the sheering qualities that I want.  This does not happen with any other color/brand/type of ink that I have used, only white (and every brand of white I have tried).  I guess my original post described a byproduct of the problem, and not the problem itself.  Using S mesh and a triple duro squeegee helps of course, but the ink is the issue.

The static electricity thing is something I am noticing more and more and probably deserves its own thread...

[Screened Gear]

My main concern is the ink losing viscosity over time instead of gaining it. White ink when properly prepared prints like butter for a while, but tenses up over time, causing it to ride up the squeegee.  It clears worse, and loses the sheering qualities that I want.

That is strange. It is backwards. Ink breaks down when printing. It will become more fluid. I print manually about 30 to 50% of my week. What ink are you using. I just have a hard time understanding how an ink can get thicker over the course of a print job. I have always see them get less thick to the point when they stabilize. Water base and plasticharge inks will thicken up that is the only ones I have seen do that.

I used Union cotton white printing manually and that is the only ink that I saw the static charge making the ink dance on the screen. It would fling ink strands all over the place when the screen had non ink covered areas.  That ink always had a good smell to me. It was a strange almost nut like smell.

[Homer]

The only issues I have with white plastisol:

1. Gumming up and climbing the squeegee, even on the creamiest inks, more than any other color.
2. The way it reacts to static electricity and flings off little strings that pull away from the mesh.

The actual printing is pretty straightforward with the right variables.

why is it climbing? do we need the feature that causes it to do that? would you (everybody here, not just mimo) sacrifice printability for less climb, or would you rather there was a lot more to clean up but it printed better?

pierre

I could give a crap about the cleanup in this regard, and am more concerned with consistency.  I am probably more concerned with ink that performs consistently over time as I print on a manual and have plenty of other variables to account for on each stroke without worrying about adjusting over time for changing ink characteristics.  My main concern is the ink losing viscosity over time instead of gaining it.  My experience is likely different from most as I am printing on a manual, but I am still preheating metal platens and pre-mixing, etc.  White ink when properly prepared prints like butter for a while, but tenses up over time, causing it to ride up the squeegee.  It clears worse, and loses the sheering qualities that I want.  This does not happen with any other color/brand/type of ink that I have used, only white (and every brand of white I have tried).  I guess my original post described a byproduct of the problem, and not the problem itself.  Using S mesh and a triple duro squeegee helps of course, but the ink is the issue.

The static electricity thing is something I am noticing more and more and probably deserves its own thread...

mimo, sounds to me like your ink is actually cooling down, not necessarily getting thicker. I know when we print, there is a more consistent movement of the ink, between flood and print stroke so it stays up to temp. the ink is constantly moving and is at rest for only a few short seconds. I know you can print pretty quick on a manual but compared to an auto, I bet your ink isn't moving nearly as fast or often making it cool down....

[jsheridan]

I'll never forget what an ink manufacturer told me in my younger days..

Ink doesn't think..

the dummy holding the bucket does.