Matsui Under Base Blocker 301-LG Black | Maximum-Density Water-Based Dye Migration Blocker for Aggressive Polyester, Sublimated Garments & Performance Fabrics — Works Under Water-Based AND Plastisol Inks
Matsui
Matsui Under Base Blocker 301-LG Black is the maximum-density dye migration blocker in the Matsui acrylic system — the escalation product for the most aggressive bleeders that standard gray blockers cannot hold. Deep black, carbon-based formulation provides the highest blocking density available for stopping dye migration on 100% polyester, sublimated garments, aggressive camo patterns, deep red and royal blue polyester, and any bleed-prone fabric that overwhelms lighter blockers. Works as an underbase under both water-based Matsui inks AND plastisol inks. Also the building block for DIY Blocker 301 Gray: blend 90% Black LG + 10% Matsui Stretch White.
Price range: $29.99 through $399.99
Description
Maximum Blocking Power — When Standard Gray is Not Enough
Blocker Black LG is the escalation product. When Blocker 301 Gray is letting bleed through on your most aggressive polyester jobs, Blocker Black LG provides the maximum blocking density available in the Matsui acrylic system.
Carbon-based deep black formulation provides the highest blocking density available in the Matsui acrylic system. The dense carbon layer creates a maximum-strength barrier against the most aggressive sublimation dye migration.
Deep red polyester, royal blue polyester, sublimated all-over-print garments, dark camo patterns on polyester — these are the fabrics that overwhelm standard gray blockers. Blocker Black LG is built specifically for these situations.
Compatible as an underbase under both water-based Matsui inks and plastisol inks. Plastisol shops can replace stiff PVC plastisol blockers with Black LG for a softer, more flexible blocker layer while maintaining the same or better dye migration protection.
Maximum blocking with zero visual impact when printing dark colors over dark polyester. The deep black blocker disappears under the top color layers.
Blend 90% Blocker Black LG + 10% Matsui Stretch White to create Blocker 301 Gray. Shops that stock Black LG can always make gray blocker when needed, eliminating the need to carry two separate blocker SKUs.
PVC-free, OEKO-TEX Standard 100 certified (suitable for baby products), CPSIA and HR4040 compliant.
When to Escalate from Gray to Black LG
For standard poly colors (navy, forest, heather grey) — Blocker 301 Gray handles these. Flash fully, test the dye migration over 24-72 hours. If the gray holds, stay with gray.
Deep red polyester, royal blue polyester, sublimated all-over-print (AOP) garments, dark camo patterns, or any garment where you see dye migration breakthrough despite using gray blocker. These colors have the most aggressive dye chemistry.
Stock Blocker Black LG always. Keep Stretch White always. When you need gray blocker, blend 90/10. When you need maximum blocking, use Black LG straight. This gives you both products from one SKU.
Best Use Cases
All-over-print sublimated garments are the most extreme dye migration challenge. The entire garment is saturated with reactive sublimation dyes. Blocker Black LG at maximum deposit is the required solution.
These garment colors contain some of the most aggressive reactive dyes. Standard gray blockers often fail. Black LG provides the blocking density needed.
Dark camo prints on polyester — particularly those with dark olive, forest, and black zones — often have aggressive bleeding. Black LG handles these reliably.
For shops printing plastisol colors on polyester, Blocker Black LG provides a softer, water-based blocker alternative to traditional plastisol blockers — with the same or better dye migration protection.
Pro Tips & Critical Notes
For maximum blocking performance, print through 110-120 mesh with a thicker-than-normal stencil. More ink deposit = thicker blocking layer = better dye migration resistance.
The blocker layer must be completely flashed before printing the next layer. Insufficient flashing leads to cracking under subsequent heat and potential bleed-through at the cracks.
90% Blocker Black LG + 10% Matsui Stretch White = Blocker 301 Gray. This gives you gray blocker from the same product.
Always test on each specific garment. Check dye migration immediately and again after 24-72 hours. Dye migration varies significantly by brand, color, and dye lot.
Technical Specifications
Matsui Under Base Blocker 301-LG Black — Technical Specifications
| Specification | Value / Detail |
|---|---|
| Product Type | Maximum-density water-based dye migration blocker |
| Color | Deep carbon black |
| Mesh Range | 110-305/inch (thicker stencil at 110-120 preferred for max blocking) |
| Cure Temperature | 320F (160C) |
| Best For | Deep red, royal blue, sublimated garments, dark camo, aggressive bleeders |
| Compatible Top Inks | Water-based Matsui inks AND plastisol inks |
| DIY Gray Blocker | 90% Black LG + 10% Matsui Stretch White = Blocker 301 Gray |
| Retarder MG | Retarder MG 1-5% for screen open time |
| Compliance | OEKO-TEX Standard 100 (baby safe), CPSIA, HR4040, PVC-free |
| CAUTION | Always test on specific garment. Dye migration varies by brand/color/dye chemistry. |
Technical Sheets / Safety Data Sheets / Documents
FREQUENTLY ASKED QUESTIONS
What does Under Base Blocker 301-LG Black do?
It stops dye sublimation migration — the process where polyester garment dyes re-gasify under heat and migrate into your ink, discoloring your print. Black LG is the maximum-density blocker in the Matsui acrylic system — the escalation product for the most aggressive dye migration situations that standard gray blockers cannot hold.
When should I use Black LG instead of Blocker Gray?
Use Black LG for the most aggressive bleeders: deep red polyester, royal blue polyester, sublimated all-over-print garments, dark camo patterns on polyester, and any garment that has bled through Blocker Gray in your testing. Also use Black LG when your top colors are dark — the black underbase is invisible and you get maximum blocking without needing a white layer.
Can I use Black LG under plastisol inks?
Yes — print Matsui Blocker Black LG first, flash at 320°F, then print your plastisol colors on top. The water-based blocker cures softer and more flexible than a plastisol blocker. That gives you maximum dye blocking with better hand feel.
Why is Black LG stronger than Gray Blocker?
Blocker Gray is a premixed blend of 90% Black LG + 10% Stretch White, so the white dilutes the carbon concentration. Black LG is the full-strength concentrate with maximum carbon density. More carbon means more dye barrier.
Can I make Gray Blocker from Black LG?
Yes — blend 90% Blocker Black LG + 10% Matsui Stretch White. Stock Black LG and Stretch White, and you can make Gray on demand while keeping Black LG available full-strength for aggressive bleeders.
Will the black underbase darken my light top colors?
It can if your white layer does not provide complete coverage over the black. Use a heavier white deposit or double-stroke your white over Black LG to fully hide it. For dark top colors, this is not an issue because the black underbase is invisible.
What mesh count should I use?
110–305/inch. Matsui specifically recommends up to 120 mesh with a thicker stencil for Black LG to achieve the heaviest deposit and maximum blocking. A thicker stencil means more blocker on the garment and a stronger dye barrier.
Which garments need a blocker?
100% polyester, especially dark and bright colors, poly blends with 50% or more polyester, Dri-Fit, sublimated garments, and camo on polyester all need a blocker. 100% cotton typically does not need one. 50/50 blends should be tested. Always test 48 hours out, because dye migration can take up to 72 hours to fully appear.
Does Black LG work on sublimated garments?
Yes — this is one of its primary use cases. Sublimated garments contain the most concentrated sublimation dyes, and Black LG provides the maximum blocking density to stop them. Always test before production.
What about Kombat Blocker?
Kombat Blocker is another Matsui blocker option for polyester dye sublimation. Test both to determine which provides the best results on your specific garment brand and dye chemistry.
Is there a blocker for the 350 Series polyurethane inks?
Yes — the 350 Series uses Under Base Blocker 350. The 301 Gray and 301-LG Black blockers are for the acrylic system and for plastisol compatibility.
Is Black LG safe for children’s clothing?
Yes. Blocker Black LG is OEKO-TEX® Standard 100 certified, suitable for baby products, CPSIA compliant, and HR4040 compliant. It is PVC-free and environmentally safe.
Why is the hand feel softer with Matsui Black LG under plastisol than with a plastisol blocker under plastisol?
The blocker layer is always the heaviest, thickest layer in the print stack. With a plastisol blocker, that heavy layer is stiff PVC. With Matsui Black LG, that heavy layer is soft, flexible, water-based acrylic. The plastisol color layers on top are the same, but the foundation underneath is dramatically softer.
Reviews
Only logged in customers who have purchased this product may leave a review.
You May Also Like
Related products
-
Matsui Under Base Blocker 301 Gray | Water-Based Dye Migration Blocker for Polyester, Performance Fabrics & Sublimation-Prone Garments — Works Under Water-Based AND Plastisol Inks
Price range: $29.99 through $399.99 -
Matsui 301M Matte White | Semi-Opaque High-Mesh Water-Based Matte Mixing Base for Custom Colors on Colored Cotton Screen Printing
Price range: $29.99 through $3,199.99 -
Matsui Gold Shimmer 620 | Water-Based Metallic Gold Shimmer Ink for Soft Luxury Screen Printing on Cotton & Blends — Tintable with Neo Pigments
Price range: $39.99 through $699.99 -
Matsui Pearl Binder 301 | Water-Based Pearlescent Iridescent Ink for Soft Luxury Screen Printing on Cotton & Blends — Tintable with Neo Pigments for Custom Pearl Colors
Price range: $34.99 through $99.99
Reviews