Triple-weave black-weft cloth achieves 85%–95% dimout without coating; 100% zero-lux blackout requires a 3-pass acrylic/foam coating or laminate.
Light-Blocking Test (AATCC 148 & JIS L 1055): Dimout vs Blackout
Light-blocking tests (AATCC 148 and JIS L 1055) measure the percentage of incident light blocked by a drapery cloth, separating 85%–95% triple-weave dimout from 100% coated blackout.
Weaverine weaves 180–280 GSM triple-weave dimout and 3-pass blackout base fabrics on extra-wide waterjet looms at 280–315 cm finished widths (5,000 m MOQ) for hospitality and contract drapery specifiers.
By Wren Thunderborn, Head of Content
AATCC TM148 and JIS L 1055 are the standard laboratory photodetector tests used to verify how much light a curtain or drapery fabric actually blocks (% Opacity or Shading Rate).
On hospitality and contract drapery purchase orders, naming the test standard prevents the most common sourcing dispute: expecting 100% zero-lux blackout from an uncoated triple-weave dimout cloth (particularly in white, cream, or beige colorways).
1. Triple-Weave Dimout vs. 3-Pass Coated Blackout
| Specification | Triple-Weave Inherent Dimout | 3-Pass Acrylic / Foam-Coated Blackout |
|---|---|---|
| Structure | 3-layer woven construction (75D face warp + dense 300D black middle weft + 75D back) | Woven polyester base (110–150 GSM) coated with 3 sequential passes of white/black/white acrylic foam (220–300 GSM total) |
Light-Blocking % (AATCC 148) | 85%–95% in medium/dark shades; 70%–85% in white/ivory | 99.9%–100% (0 lux pin-hole free across all face colors) |
| Hand Feel & Drape | Soft, fluid, double-sided textile drape; reversible | Firmer, coated reverse face; stiffer pleat memory |
Commercial Laundry (ISO 6330) | Machine-washable at 60 °C; no coating to crack or peel | Sensitive to high-temperature extraction and folding creases |
| Finished Mill Width | 280–315 cm (seamless railroaded floor-to-ceiling drops) | Typically 150–280 cm (limited by coating head width) |
2. How the Calculation & JIS L 1055 Grading Work
Both AATCC TM148 and JIS L 1055 measure incident illuminance () without the specimen and transmitted illuminance () with the fabric clamped across the aperture:
Light Blocking (%) = (1 − Et ÷ E0) × 100%
In Asian and international contract specifications, buyers frequently reference the JIS L 1055 Shading Rate classes:
JIS L 1055 Grade | Light-Blocking Range | Typical Construction Required |
|---|---|---|
Class 1 (1級 · Tier A) | ≥ 99.99% (0 lux visual) | 3-pass / 4-pass foam-coated blackout or laminated film |
Class 1 (1級 · Tiers B–C) | 99.40% – 99.98% | Heavy 280+ GSM ultra-dense dark triple-weave or 2-pass coated dimout |
Class 2 (2級) | 99.80% – 99.98%(older scale 99.0%–99.39%) | High-density dark-dyed triple-weave dimout (240–280 GSM) |
Class 3 (3級) | 99.40% – 99.79%(or commercial 85%–95% dimout) | Standard 180–240 GSM triple-weave dimout |
What to Put on the Purchase Order
- State construction + target % by shade: e.g.,
240 GSM Triple-Weave Dimout, AATCC 148 ≥ 90% on dark shades / ≥ 78% on ivory, or260 GSM 3-Pass Coated Blackout, AATCC 148 = 100%. - Pair
AATCC 148light blocking with light fastness (ISO 105-B02Grade 4–5+) so window-side curtains do not fade under UV exposure. - Specify wide-width 280–315 cm finished width and calculate panel consumption in the Curtain Yardage Calculator. See our blackout fabric catalog (
5,000 mMOQ).
Common questions
How is blackout curtain light blocking tested in a lab?
- Under AATCC TM148 (Photodetector Method) and JIS L 1055 (Illuminance Method), a specimen is clamped between a calibrated light source and a lux photodetector. Light-blocking percentage is calculated as (1 − Transmitted Illuminance / Incident Illuminance) × 100%.
Why does the same triple-weave dimout construction block 95% light in navy/charcoal but only 75%–82% in white/ivory?
- In an uncoated triple-weave dimout, a dense black polyester yarn sits in the middle layer while the face and back yarns carry the decorative shade. Dark face dyes absorb stray photons entering the surface, whereas white or pastel face yarns scatter light across the middle black weft.
What are JIS L 1055 Class 1, Class 2, and Class 3 shading grades?
- JIS L 1055 grades drapery shading rate into three classes: Class 1 (≥ 99.40% light blocking, subdivided into Class 1A ≥ 99.99%), Class 2 (99.80%–99.98%), and Class 3 (99.40%–99.79%).
When should a hotel specify dimout vs 3-pass coated blackout?
- Specify 220–260 GSM triple-weave dimout when the curtain must drape softly, wash at 60 °C without coating peel, and block 85%–95% of light. Specify 3-pass foam-coated blackout (or a separate 3-pass blackout lining behind a decorative face) when the room specification demands 100% zero-lux darkness.
Related Terms
Sourcing blackout light-blocking test or a polyester equivalent? We quote mill-direct programs from 5,000 m per specification.
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