Matsui Kombat Blocker — Built for the Hardest Bleed in Polyester

Standard dye migration is hard enough. The garment dyes in a dark red jersey start moving when heat hits them, bleeding through your white overprint and turning it pink. Every screen printer who works with polyester knows this problem.

But sublimation-printed polyester is a different level of difficulty entirely.

Sublimation printing works by heat-activating dyes. The entire sublimation process is simple: apply dye, apply heat, dye becomes gas, and the dye bonds to polyester fibers. That process is what creates the sublimation print in the first place. Now, when you screen print on top of that sublimation-printed fabric and run the garment through your dryer at 320°F to cure your screen-printed ink, you are applying the same heat that originally activated those sublimation dyes. The sublimation dyes re-activate. They become gaseous again. They migrate upward, right into your freshly printed screen-print layer.

The result is exactly what printers hate: your white turns pink, yellow, blue, or whatever color the sublimation design underneath contains. Your black gets a color cast. Your custom-mixed color shifts off-Pantone. The sublimation dyes contaminate every overprint layer they can reach.

Standard blockers — Under Base Blocker Gray and Under Base Blocker Black LG — are excellent at blocking dye migration from standard dyed polyester. But sublimation-printed polyester generates more aggressive dye migration because the dyes are specifically designed to be re-activated by heat.

Kombat Blocker is the enhanced-formula answer. Its formulation is specifically improved to block dye migration from sublimation-printed fabrics, which is the most demanding dye migration scenario in textile screen printing.

The Kombat System — Blocker, White, and Black

Kombat Blocker is part of a purpose-built three-product system for performance fabric printing.

Kombat Blocker — the enhanced dye migration barrier. Print it first and flash it. It blocks sublimation dyes and standard polyester dyes from migrating into the overprint layers.

Kombat White — the performance white. Print it over the blocker after flashing for bright, elastic white on performance fabrics. It offers superior whiteness, anti-foil stickiness, and can be mixed with Neo Pigments for custom stretch colors.

Kombat Black — the performance black. Print it over the blocker after flashing for deep, rich black with excellent elasticity on stretch garments. It is designed for both halftone and spot printing and meets major sports apparel manufacturer standards.

The production sequence on sublimation-printed polyester is straightforward:

Kombat Blocker → flash → Kombat White for white elements → flash → Kombat Black for black elements → flash → colors as needed → final cure at 320°F (160°C).

The blocker goes down first. Everything else prints on top of the blocker. The blocker is the shield between the sublimation dyes in the fabric and the screen-printed inks on the surface.

Kombat Blocker vs. Blocker Gray vs. Blocker Black LG — Three Blockers, Three Tiers

Matsui makes three dye migration blockers. Each one is designed for a different level of dye migration severity.

The escalation path: Start with Blocker Gray for standard polyester. If Gray does not hold, move to Blocker Black LG for more aggressive dyes. If Black LG still does not hold on sublimation-printed fabrics, move to Kombat Blocker — the enhanced formula built for the worst-case scenario.

Why Sublimation-Printed Polyester Is the Hardest Migration Challenge

Understanding why Kombat Blocker exists requires understanding why sublimation dyes are different from standard garment dyes.

Standard polyester dyes are heat-set during manufacturing. They are relatively stable at the 320°F cure temperature used for screen printing. Some migration still occurs, but a strong blocker like Gray or Black LG can usually contain it.

Sublimation dyes are designed to become gaseous at elevated temperatures, generally between about 350°F and 400°F, and they begin transitioning below that range. At 320°F, sublimation dyes are already mobilizing. They are at the bottom of their activation range but still generating significant gaseous migration. The dye literally turns into gas and rises through any layer above it, including your blocker if that blocker is not formulated to handle that level of migration pressure.

This is why you can successfully print on a standard dark polyester jersey with Blocker Gray, but the same blocker may fail on a sublimation-printed jersey. The sublimation dyes generate dramatically more migration force at the same cure temperature.

Kombat Blocker’s enhanced formulation creates a denser, more effective barrier against this higher migration pressure.

Pre-Test on Actual Production Fabric

This cannot be overstated: pre-test Kombat Blocker on the actual production fabric before running the job.

Dye migration varies across polyester types, dye lots, sublimation print densities, garment brands, and even different batches from the same manufacturer. A sublimation print with heavy, saturated color coverage generates more migration than one with lighter coverage. A deep red sublimation design migrates more aggressively than a pastel blue sublimation design.

Print Kombat Blocker on a test garment from the actual production fabric. Flash it. Print your overprint layer. Cure it. Wait 48 hours. Check for migration. If the blocker holds, proceed to production. If migration is still visible, increase deposit thickness by using lower mesh or a thicker stencil and test again.

How Matsui Additives Improve Your Production with Kombat Blocker

Kombat Blocker is production-ready from the container. Matsui additives can help optimize the production process.

The problem: Blocker dries in the screen during production pauses. The additive solution: Retarder MG at 1–5% extends open time.

The problem: Overprint layers fade or degrade after washing. The additive solution: Fixer WF-N at 1–5% crosslinks the binder for improved wash fastness.

Additional additives include Thickener B at 0.25–1% to increase viscosity for better deposit control and RV Additive at 1–3% to reduce viscosity if the blocker feels too thick.

Browse the complete Matsui additive collection here.

Printing Tips for Maximum Dye Migration Blocking

Thick stencil = better blocking

Use multiple emulsion coats or capillary film to build a thick stencil. The thicker the blocker deposit, the more effective the dye migration barrier becomes. On sublimation-printed fabrics, a heavier-than-normal deposit is recommended.

Mesh selection

Print through mesh up to 120/inch (47/cm). Lower mesh deposits more blocker for better dye containment. For the most aggressive sublimation prints, use 80–110 mesh for maximum deposit.

Flash before overprinting

Flash the blocker layer before printing any overprint layers such as white, black, or colors on top. The blocker must be set before it can function as a barrier.

Full coverage

The blocker must cover the entire area that will receive overprint, including any bleed or trap beyond the visible design edges. Any uncovered area creates an open path for dye migration.

48-hour test rule

After your test print, wait 48 hours before evaluating it. Some dye migration is not immediately visible and develops over time as residual thermal energy dissipates. What looks clean at one hour may show migration at 48 hours.

Why Screen Printers Choose Kombat Blocker

I print on sublimation-printed jerseys and team uniforms, and standard blockers are not stopping the migration.

This is the number one reason Kombat Blocker exists. Sublimation dyes re-activate at cure temperatures and create more migration pressure than standard polyester dyes. Kombat Blocker’s enhanced formulation is built for this exact challenge.

I need the complete Kombat system for sublimation-printed performance fabric.

Kombat Blocker → flash → Kombat White → flash → Kombat Black → cure. These three products are designed to work together on the most demanding polyester substrates.

I screen print over sublimation prints, adding names, numbers, or sponsor logos to sublimation-printed jerseys.

This is one of the most common Kombat Blocker applications. The sublimation print covers the jersey, and then screen-printed names, numbers, and sponsor logos are added on top. Kombat Blocker goes down first to prevent the sublimation design from bleeding into those white numbers and text elements.

My Blocker Gray works on regular poly but fails on sublimation-printed fabric.

That is exactly the escalation path Kombat Blocker was designed for. Blocker Gray handles standard polyester dyes. Sublimation dyes exceed its blocking capacity. Kombat Blocker is built for that higher migration pressure.

I need maximum blocking with the best chance of success on unknown or untested sublimation fabrics.

When you receive sublimation-printed garments from an unknown source and cannot fully predict their dye behavior, Kombat Blocker gives you the best chance of containing migration. Use a thick deposit at low mesh and follow the 48-hour test rule before committing to full production.

Key Features

• Enhanced formula for sublimation-printed polyester — specifically improved for the most aggressive dye migration scenario in screen printing
• Part of the Kombat system — pairs with Kombat White and Kombat Black
• Blocks standard polyester dyes too — effective on standard dyed polyester as well as sublimation-printed substrates
• Thick stencil recommended — heavier deposit creates a better migration barrier
• Pre-test required — always test on actual production fabric before committing to the run
• Production-optimized with Matsui additives — compatible with Retarder MG, Fixer WF-N, Thickener B, and RV Additive
• Zero viscosity modifications required — prints from the container
• PVC-free and eco-friendly — environmentally safe
• Drop-shipped from Matsui — ships directly from Matsui in Gardena, California, with an additional 2–3 days processing time

Recommended Additives for Kombat Blocker Production

Browse the complete Matsui additive collection here.