SEG Fabric Weight: 110, 160 or 260 gsm?

SEG fabric weight is measured in grams per square metre (gsm), and it is one of the first numbers a buyer should fix before ordering a light box graphic. Weight decides how much light passes through, how flat the face stays, and how the print reads up close. This guide compares the three common weights and tells you which questions to put in the RFQ.

What Fabric Weight Actually Means

Gsm is the mass of one square metre of textile. A higher number means a denser weave or knit, thicker yarn, or both. In backlit applications the fabric has two jobs at once: carry the printed image and pass light evenly. Those jobs pull in opposite directions, which is why weight is a trade-off rather than a quality grade.

Weight is not the same as opacity. Two 160 gsm fabrics from different mills can block light differently because the weave structure differs. That is why the RFQ should ask for weight plus a light transmission figure, not weight alone.

Why Buyers Care About Weight

The wrong weight shows up in three ways. A fabric that is too light lets the LED pattern show through as bright patches. A fabric that is too heavy swallows light, so the face looks dull unless the LED count rises. And a fabric with the wrong stretch behaviour relaxes after install, leaving ripples across the face.

• Light transmission. Heavier fabric blocks more light; the same frame may need more LEDs to hit the same brightness target.
• Print feel. Dense weaves hold fine text better; open knits suit bold colour fields.
• Tension life. Weight plus weave decides how the fabric relaxes over months of temperature change.
• Shipping. Weight per graphic adds up across a multi-store rollout.

How Weight Shapes the Light

A light box face is a three-layer system: LEDs, air gap, fabric. Light leaves the LEDs, spreads across the gap, then passes through the textile. The fabric acts as the final diffuser. A lighter fabric passes more light but diffuses less, so the LED pitch must be tighter. A heavier fabric diffuses well but absorbs more, so the brightness target must be set with that loss in mind.

This is why changing fabric weight after the frame is quoted can invalidate the brightness calculation. Weight, LED pitch and frame depth belong in one specification, agreed together.

Where Each Weight Fits

Weight class	Typical character	Where it works
Around 110 gsm	Light knits; high transmission; visible texture up close	Large ceiling or hanging faces viewed from a distance; budget campaign runs
Around 160 gsm	Standard backlit balance; even diffusion; good print detail	Retail walls, windows and most indoor SEG light boxes
Around 260 gsm	Dense weave; low transmission; near-blockout; strong tension	Double-sided boxes that must not show the reverse image; premium close-view walls

These are planning classes, not catalogue promises. Mills differ, and a 160 gsm knit can behave like a lighter woven fabric. Confirm the actual transmission figure with a sample.

110 vs 160 vs 260: What Really Changes

Consideration	110 gsm	160 gsm	260 gsm
Light transmission	Highest	Balanced	Lowest
Show-through risk	Higher on tight LED pitch	Low with correct pitch	Minimal
Print detail	Softer edges	Crisp text and gradients	Crisp; premium feel
Tension behaviour	Relaxes faster	Stable	Very stable; needs deeper groove engagement
Shipping weight	Lightest	Standard	Heaviest
Typical job	Long-distance viewing	General retail	Close viewing, double-sided

Fabric Weight vs Fabric Opacity: Not the Same Spec

Buyers sometimes write “heavy fabric” when they mean “no show-through”. Opacity is the property that blocks the reverse image; weight is only one of its inputs. Weave density, yarn type and coating all contribute. A purpose-made blockout fabric can out-perform a heavier standard knit. Ask for the transmission percentage and, for double-sided units, a sample lit from one side.

The related decision is backlit fabric versus blockout fabric for non-illuminated graphics; that comparison is covered in a separate guide and follows different logic.

When Heavy Fabric Is Worth It — and When It Isn’t

Worth it	Skip it
Double-sided unit; reverse image must not show	Single-sided face where brightness is the priority
Close viewing under 1 m with premium finish	Large hanging banner read from several metres
Long campaign life with repeated graphic changes	One-off event with a short service window
Frame depth already matched to low transmission	Shallow 30 mm frame quoted for a light knit

How to Set Fabric Weight in an RFQ

1. Fix the brightness target first. Weight follows the light budget, not the other way round.
2. Ask for gsm plus transmission. Two numbers, from the actual mill lot, not a datasheet copy.
3. Request a lit sample. View it in the frame, at the viewing distance, before the batch prints.
4. Confirm the fire standard for your market. Ask which test standard the fabric carries and request the report for the specific lot.
5. Lock the edge spec. Weight changes thickness; the silicone edge and groove must still match.
6. Record the choice on the template. The next reorder should reference the same fabric, not just “SEG fabric”.

Common Mistakes Buyers Make

• Choosing weight from a photo. Transmission and texture cannot be judged on screen.
• Copying another project’s spec. Their frame depth and LED pitch are not yours.
• Ignoring the edge. A heavier graphic needs the right bead fit or corners pop out.
• Forgetting cleaning. Open knits hold fingerprints; dense weaves wipe clean.
• Assuming one weight fits every frame in the rollout. Mixed depths may need mixed weights.
• No retention sample. Without one, later batches drift and disputes stall.

Common Questions About This Topic

What does gsm mean for SEG fabric?

Grams per square metre. It measures fabric density. In backlit graphics it drives light transmission, print detail and tension behaviour, so it belongs in the RFQ next to the brightness target.

Which fabric weight should I choose for a light box?

Most indoor retail faces settle around 160 gsm because it balances transmission and print detail. Choose lighter knits for long-distance faces and denser weaves when show-through must be blocked or the viewing distance is short. Confirm with a lit sample before a batch.

Does heavier fabric make the light box dimmer?

It can. Denser fabric absorbs more light, so the same LED count delivers a lower face brightness. If you move to a heavier weight after quoting, ask the factory to re-check the brightness calculation.

Is fabric weight the same as opacity?

No. Opacity is how much light and image show through; weight is only one input. Weave structure and coatings matter as much, so ask for a transmission figure and a sample rather than weight alone.

Can I mix fabric weights across one rollout?

Yes, when frame depths or viewing distances differ between locations. Keep one template system and record which weight belongs to which frame type.

What fire standard should SEG fabric meet?

It depends on the destination and venue. Ask the supplier which test standard the fabric carries and request the report for the specific lot, because venue rules differ between markets.

The Bottom Line on SEG Fabric Weight

Weight is a system decision, not a fabric choice. Fix the brightness target, then let the frame depth, LED pitch and fabric weight settle together. Ask for gsm and transmission as two separate figures, view a lit sample in the real frame, and record the combination on the artwork template so every reorder lands identical.

Spec block to copy into your RFQ

• Fabric weight: ____ gsm (target class: light / standard / heavy)
• Light transmission: ____ % measured on the mill lot
• Weave: knitted / woven; finish: backlit / blockout
• Silicone edge: ____ mm bead, matched to groove
• Brightness target: ____ cd/m² at the face, measured at nine points
• Fire test standard and report number for the lot: ____
• Retention sample: one graphic per order, stored flat

A supplier who answers every line has the process to hold the spec. A supplier who answers “standard” has not measured it. That single reply tells you most of what you need before the first order.

Why Buyers Work With BrandMate Display

• Direct factory supply. Printing, framing and LED assembly run under one production plan.
• Written specification. Fabric weight, edge spec and light targets are confirmed on a drawing before production.
• Product-specific QC. Graphics are checked with the light on, not on the print table alone.
• Export packing planned. Graphics roll or flat-pack separately from hardware, with faces protected.
• Reprints and spares. Replacement graphics reorder against the original template.
• One contact. The person who quoted the job answers production questions.

We will reply within 2 hours.

You can also use the contact page and attach a drawing, a site photo or your artwork file.

Related Reading

• SEG fabric light box product page — sizes, frame depths and RFQ fields.
• LED light box technical specifications — brightness, uniformity and fabric parameters.
• SEG brightness targets — set the number the fabric must deliver.
• Contact page — send sizes, quantity and destination.