Care and feeding of a white ink

[Joe Clarke]

White ink seems to be 50% of the consumption but at times 95% of the issues on press.
Here are a few generic suggestions about managing your whites prior to & during production.

White ink:
Never intermix brands or series.
High fabric-mass-easier to bridge.
Longer staple lengths-easier matte.
When using a barrel pump, don’t stir.
If print 100 matches print two, don’t stir.
The slippery slope is 115°F, DON’T EXCEED.
Summertime in Nashville, mosdef don’t stir!
Ink thins during press run, wait it out … ouch!
Hand stir quarts, for gallons & fivers;  automate.
Helix mixing paddles raise the lower ink to the top.
5 - gallon paddle types don’t, and they run ~ 60 RPM.
Helix type, 3/8” drill 600 RPM >100x shear-rate vs paddle.
The cheap, meat thermometer works well to monitor temp.
2-min. helix cooler than ~ 2-hrs. on paddle, same shear-rate.
If helix ink doesn’t clear well the problem is tack, not viscosity.
Peanut Butter, Honey, Suntan Oil are high tack, Cold Cream isn’t.
Stirring can break-up weak, temporary bonds, tack is permanent.
No amount of stirring, warming or pumping will reduce the ink tack.
Stirring is meant to redistribute the particles, heating is a by-product.
Warming is short lived, increases tack but doesn’t redistribute particles.
The warming process can be prior to production or during from the flash.
Higher tack ink is directly proportional to overheating and increasing tack.
When we flash curing, NEVER return used white ink to the virgin container.
Ink thickens during press run, reduce flash distance first then its temperature.
Proper high-shear, high-speed ink transfer runs cooler than traditional transfer.
Shear thinning white inks w/ >5.0:1 ratio can be printed at top print stroke speeds.
Inks w/ tack level greater than 35% should be stirred and printed at very slow speeds.
Curable Reducer will increase flash time, causes after tack and compromises durability.
After proper stirring print #5 won’t clear, wrong; ink, mesh, blade, stencil, press settings.
Low tack white [<35%] on high ink transfer mesh, fitted blades & press; clears on first pass.

[ScreenFoo]

Interesting list.

I have never seen tack expressed as a percentage, or shear thinning as a ratio like that.
How does one go about measuring them?

[tonypep]

This, my friend, is why we love white discharge and colors. My printers don't like dealing with dealing with plastisol, especially white. Its also why we were referred to for large volume contract continuous business by an ink manufacturer

[Joe Clarke]

Both tack and shear-thinning properties require lab equipment to quantify but it is equipment every ink maker should have. It is most certainly "the hard way" but we gauge tack [~how the white adheres to iteslf VS how it adheres to something else] every day on press. Ink which has excessive tack won't bridge or matte-down easily, it requires a lot of squeegee angle and / or pressure, doesn't clear the mesh well and tends to leave a rough surface. Shear thinning is a ratio of two viscosities [~the friction between two fluid layers of ink]; flooded viscosity and transferring viscosity. We want the tack ratio to be low as possible and to a limit we want the shear-thinnning ratio to be as high as possible.

[Joe Clarke]

Interesting list.

I have never seen tack expressed as a percentage, or shear thinning as a ratio like that.
How does one go about measuring them?

Both tack and shear-thinning properties require lab equipment to quantify but it is equipment every ink maker should have. It is most certainly "the hard way" but we gauge tack [~how the white adheres to iteslf VS how it adheres to something else] every day on press. Ink which has excessive tack won't bridge or matte-down easily, it requires a lot of squeegee angle and / or pressure, doesn't clear the mesh well and tends to leave a rough surface. Shear thinning is a ratio of two viscosities [~the friction between two fluid layers of ink]; flooded viscosity and transferring viscosity. We want the tack ratio to be low as possible and to a limit we want the shear-thinnning ratio to be as high as possible.

[3Deep]

This, my friend, is why we love white discharge and colors. My printers don't like dealing with dealing with plastisol, especially white. Its also why we were referred to for large volume contract continuous business by an ink manufacturer

Yeah Tpep, but you can't discharge everything or cannnnnnn you LOL,  using discharge white is very nice if I could I would use it on everything and not use plastisol white at all.

darryl

[tonypep]

Pretty much everything except performance wear which we don't do. We have several DC/UB formulas for the stubborn ones. Also expanding the DC color offering to accommodate new business.

[farmboygraphics]

So you're saying I can use cold cream to reduce tack...sweet!! ;-)

[Joe Clarke]

So you're saying I can use cold cream to reduce tack...sweet!! ;-)

Only if you first warm the cold cream in a hot oven or preferably a ceramic kiln then gently stir.

[farmboygraphics]

So you're saying I can use cold cream to reduce tack...sweet!! ;-)

Only if you first warm the cold cream in a hot oven or preferably a ceramic kiln then gently stir.

Well I now have cold cream all over the bottom of my kiln and it stinks to high hell in here. Should I have used one of the glass jars? Dang!

[starchild]

Both tack and shear-thinning properties require lab equipment to quantify but it is equipment every ink maker should have. It is most certainly "the hard way" but we gauge tack [~how the white adheres to iteslf VS how it adheres to something else] every day on press. Ink which has excessive tack won't bridge or matte-down easily, it requires a lot of squeegee angle and / or pressure, doesn't clear the mesh well and tends to leave a rough surface. Shear thinning is a ratio of two viscosities [~the friction between two fluid layers of ink]; flooded viscosity and transferring viscosity. We want the tack ratio to be low as possible and to a limit we want the shear-thinnning ratio to be as high as possible.

So share thinning, is how easily the ink inside the mesh funnel, separates from the top layer of itself, as the squeegee's edge passes over the mesh opening? If this is interpreted this way, if the ink tack ratio is low, one of the attributes of the ink would be that the shear-thinning ratio would be (on the positive side of things) high? So one measurement does not work independently of the other- right? Like you said a high tack ink won't separate from itself well.

And what causes the ink to be high tack in the first place?

[Colin]

Certain liquid components and resin choices.

One example is Mineral Spirits.  Its a filler liquid. 

I personally hate it....

[tonypep]

I know of one 3rd wld op that siphoned gasoline from a jeep to thin ink for..............get this......................kids wear

[Ross_S]

Tony;

I'm not surprised at all by that.  I know I've seen some crazy stuff in my earlier years working for people (Flat Stock and graphic printers are the worse).  Also, bet that people in this country are oblivious to how some of their kids apparel is produced and more than likely paid double for it.

Joe;

I'm bowing through your ink like crazy so I hope your making a crap ton if that stuff cause I'm averaging a gallon to two gallons a day of that stuff (Good Ink)

[mk162]

Reminds me of the shop that cleaned screens with gas.  Gallon container under the press...paper towels soaked in it...and they smoked in the shop as well.