Why “Pre-Shearing” Your Plastisol Ink is Essential for Better Prints

When I’m not on the road working with printers in their shops, I’m often answering tech calls and emails for Avient inks. Many of those conversations cover the same few topics—so much so that my son, who’s been stuck in the car with me during these calls, could probably explain proper Plastisol handling to you himself.

One of the most common points I explain—sometimes several times a day—is the concept of pre-shearing.

What is Pre-Shearing?

Plastisol inks are both pseudoplastic and thixotropic. That means they shear-thin—their viscosity decreases—when subjected to stress or agitation over time. At rest, the ink regains body, becoming thicker and more resistant to flow through your mesh.

When you scoop ink from the bucket and put it directly into the screen without preparation, you’re trying to print with an ink that’s still in its “resting” state—thicker, stiffer, and harder to pass through the mesh.

Think Honey

Imagine a new bottle of honey you’ve just brought home. Turn it upside down and it won’t instantly flow. But stir it with a spoon and the structure breaks down—suddenly it pours much more easily. Plastisol behaves the same way.

How to Pre-Shear Plastisol

Before loading the ink into your screen:

• Use an ink knife or sturdy stirring tool.

• Stir, fold, and cut through the ink in the bucket.

• Work it until it flows off your ink knife like honey when lifted.

This mechanical action breaks down the internal structure built up during storage, making the ink more fluid and easier to print right from the start.

Why It Matters

If you’ve noticed that your prints look better toward the end of a run, that’s because the squeegee and flood bar have been shearing the ink in the screen with every pass. By pre-shearing before you start, you’ll get consistent flow, opacity, and print quality from the very first shirt.

Bonus Cold-Weather Tip

During colder months, Plastisol can develop excessive body simply from being stored in a cold shop. To prevent this:

• Store inks off cold concrete floors—on shelves or wood blocks with an air gap beneath the bucket.

• Avoid quick warming—don’t set buckets on top of a dryer or under a flash to heat them.

If the bucket feels warm to the touch, the ink is likely being damaged. While it may flow better warm, once it cools, it will body up even more and become increasingly difficult to print with—especially after returning excess ink to the bucket.

Bottom line: Don’t fight stiff ink—wake it up before you print.