screen-printing

HOW TO REDUCE PLASTISOL INK

7 July 2026

This is the guide we'd hand a new starter on their first week around the ink room. It covers what a reducer actually is, when to reach for it, how much to add, how to mix it properly, and how to prove the print still cures. Take the ten minutes. Reducing ink is one of those jobs that's dead simple to do and just as simple to do wrong, and the wrong version doesn't show up until a customer washes the shirt.

What a reducer is, and why "curable" matters

Plastisol ink is basically PVC particles suspended in plasticiser. It doesn't dry in the screen, and it doesn't cure until you take the whole ink film up to fusion temperature. A reducer is an additive that lowers the ink's viscosity so it flows, clears fine mesh, and lays down a thinner, softer deposit.

The word that matters is curable. A curable reducer is made from the same family of chemistry as the ink, so it fuses and cures right alongside it at the ink's normal cure temperature. Avient, the company behind Wilflex and Union, puts it plainly in their reducers bulletin: curable reducer added at the recommended amounts will not alter the cure temperature of the ink.

Non-curable modifiers are a different story. They thin the ink, but they don't become part of the cured film. International Coatings warns that their own non-curable plasticiser, used in excess, "will cause fusing or curing problems" and will greatly lower the bleed resistance of low-bleed inks. Random solvents and thinners that were never made for plastisol are worse again. If the label doesn't say curable, it doesn't go in the ink. That's the shop rule.

Before you reduce anything: stir and warm

Here's the thing most new operators don't know. Plastisol is thixotropic, which means it has a false body when it's been sitting. Straight out of the bucket it reads far thicker than it actually prints. Shear breaks that false body down: stirring it, working it with the squeegee, even the heat the stirring generates all loosen the ink into its true, creamier viscosity.

Avient's reducers bulletin puts it first in their printing tips: stir inks thoroughly. Ink makers keep repeating that line because printers keep skipping it, and they too frequently add reducer to ink that never needed it. A minute or two of proper stirring with a stainless steel spatula fixes more "thick ink" problems than any additive. Pigments also settle over time, so stirring redistributes them; stiff ink is not spoiled ink.

Temperature stacks on top of that. Cold ink always reads thicker than it prints. Warm the ink to production temperature before adding any reducer, because judging cold ink almost guarantees you over-thin it. If the shop's cold, get the bucket near the press (never near the dryer or flash) and stir it before you judge anything.

A quick consistency check: park a stir stick in the ink. If the stick stands up on its own, the ink is too thick. At a good printing consistency, ink mostly clings to the stick with a slight drip, without stringing a thick thread back into the bucket.

So the order of operations is: stir first, warm ink, judge again. Only then decide whether the ink actually needs reducer.

When to reduce, and when not to

Reach for curable reducer when:

The ink drags or skips through a high mesh count
Fine detail and halftone dots are filling in
You want a softer hand feel on the finished print
The ink is genuinely too heavy-bodied for the job after a proper stir

Leave it alone when:

You haven't stirred yet. Stir first, always
The ink is cold. Warm it and re-judge
You're trying to rescue ink that's old, contaminated, or half-cured. Reducer dials in good ink, it doesn't resurrect bad ink
You're printing a low-bleed ink on polyester and your reducer isn't rated low-bleed. More on that below

How much to add

Every manufacturer publishes a range, and they're tighter than most people think. By weight, not by eye:

Avient Curable Reducer (K2915), the one on the shelf at Jones Brothers Printechnology: up to 10 percent. Avient's bulletin says a 5 percent addition by weight lowers the viscosity of most plastisols by around 25 percent, which tells you how little you actually need. Within range it will not shift the ink's cure temperature. Past 10 percent you are trading away opacity, bleed resistance and cure
Avient Viscosity Buster (K2910) and Viscosity Buster LC (K2912): 0.5 to 3 percent, hard cap. Concentrated reducers, best kept for heavy-bodied whites and blockers. Start at half a percent and move in half-percent steps
The other big names run the same way. International Coatings' standard curable reducer is 1 to 10 percent and their low-bleed version 1 to 5, FN-INK says no more than 5, Ecotex Rapid Cure is 2 to 5. Different labels, same discipline

The pattern across every data sheet: start at 1 to 2 percent, work in small additions, treat 5 percent as your everyday ceiling, and never pass 10. Past 10 percent you're trading away opacity, and on low-bleed inks you can compromise bleed resistance and even shift cure behaviour.

One more thing the data sheets agree on: reduction is one-way. You can't un-reduce an ink. Over-thin a bucket of navy and you now own a bucket of slightly lighter, slightly weaker navy. Mix small batches in a separate container rather than dosing the whole tub.

Practical maths: 2 to 5 percent by weight is 20 to 50 grams of reducer per kilo of ink, or 0.2 to 0.5 grams per 10 grams if you're testing small. Zero the scale with the container on it, weigh the ink, then weigh the reducer in. A cheap kitchen scale makes every batch repeatable; eyeballing makes every batch a guess.

Mixing it properly

Use a stainless steel spatula or a proper ink mixer. Avoid wood and cardboard, which absorb plasticiser and mess with consistency
Add the reducer gradually while stirring, and stir thoroughly until it's fully worked through
Stop as soon as the ink moves the way you want. You can always add more, you can never take it out
Label the container with the ink, the reducer percentage, and the date, so the next person isn't guessing

The low-bleed trap

This one bites shops that print polyester and blends. Low-bleed inks are formulated to resist dye migration, the thing where the shirt's dye gasses into your white print and turns it pink. Generic curable reducers undo that protection. International Coatings states outright that their standard 1110 reducer "should not be used in low bleed inks since it can lower the bleed resistance", and FN-INK carries the same warning on their reducer.

If the job is on poly or a blend and you're running low-bleed ink, use a reducer specifically rated low-bleed (that's the entire point of ICC's 1099), keep the percentage at the bottom of the range, and wash test before the production run. If in doubt, ask Jones which additive suits the ink you're on before you mix. That's the whole point of a supplier who picks up the phone.

Prove it still cures

Reducing within range shouldn't change your cure temperature, but the print still has to be proven, because an under-cured print looks perfect coming off the belt and falls apart in the wash.

Know your number. Most standard plastisol fully cures at 160 degrees Celsius (320 Fahrenheit) through the entire ink film. Plastisol starts to gel well below that, from around 82 to 121 degrees, which is exactly why a print can feel dry and still be under-cured underneath. Low-cure inks run cooler, some around 127 to 132 degrees. The ink's technical data sheet is the source of truth, not memory.

Measure properly. The whole ink film has to reach cure temp, not just the surface. A laser temp gun reads reflective surfaces optimistically, so treat gun readings as a rough guide and aim above target. A donut probe through the dryer gives the real story.

Stretch test. Stretch the print to about two thirds of the shirt's stretch. Cured ink stretches with the fabric; under-cured ink cracks like dry earth and doesn't recover. Note it's unreliable on thick deposits, where the top cures and the bottom doesn't.

Wash test. The definitive one: hot water, strong detergent, five to ten washes. A seriously under-cured print will visibly deteriorate inside one to three washes. Wash test any new ink, any new additive combo, and any job on poly.

Over-cure is real too. If the print shows an oily halo (plasticiser bleeding out) or cracks and flakes after washing despite hot readings, you may be cooking it. Dial the dryer, don't just crank it.

The mistakes that keep happening

Reducing before stirring. The number one one. Half the time the ink was fine
Reducing cold ink. It reads thick, you over-thin it, and it prints like water when the shop warms up
Eyeballing instead of weighing. "A splash" is not a percentage
Dosing the whole bucket. Reduce a working batch in a separate container
Skipping the test print. Check bleed, opacity on a dark garment, and colour strength before production
Using a generic reducer in low-bleed ink on poly. That's how white prints go pink
Assuming every brand behaves the same. Ranges differ. Read the TDS for the ink and the reducer
Passing 10 percent. Opacity, bleed resistance, and cure are all on the line up there

Where to get it

Jones Brothers Printechnology in Campbellfield VIC carry the Avient Curable Reducer in quarts, gallons and 5 gallon pails, alongside the rest of the Avient additive range and the Maxopake and Avient mixing systems. Thirty-plus years in screen printing supply, and they answer the phone with actual answers: (03) 9357 5767 or info@jonespt.com.au. They're on Instagram at @jonesptaus
CCG Industries in Auckland ship across New Zealand and Australia and list the K2915 Curable Reducer alongside Finesse and Soft Hand Clear, plus plastisol ranges from Wilflex, Union, Rutland and FN-INK

If the job's on polyester, say so when you order. Either crew will point you at the right low-bleed combination before dye migration turns your whites pink.

The new starter checklist

Print this bit and stick it near the ink room scale.

Stir the ink thoroughly with a stainless spatula, one to two minutes minimum
Warm the ink to shop production temperature, away from dryers and flashes
Re-judge. Stick test: if the stir stick stands up, it's still too thick
Confirm the reducer is curable, and low-bleed rated if the ink is low-bleed
Decant a working batch into a separate container and weigh it
Add reducer at 1 to 2 percent by weight. Stir fully
Test the flow. Add in 1 percent steps only if needed. Everyday ceiling 5 percent, hard stop 10
Label the batch: ink, reducer, percentage, date
Pull a test print. Check opacity on a dark blank, edges for bleed, and colour strength
Cure at the ink TDS temperature (160 degrees for most standard plastisol) and verify with a probe or careful gun readings
Stretch test, then wash test anything new or anything on poly
Log what worked so the next batch starts from knowledge, not guesswork

Sources

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