Is Core-Spun Glass Fiber just Fiberglass? Yeah, Pretty Much. may earn commissions from Amazon and other affiliates through links in this article.

Mattresses containing fiberglass have been a hot topic for the past few years. Finding a mattress with no fiberglass is a big concern for many consumers when it comes time to buy a new mattress. The reason is that fiberglass can leak from mattresses, contaminate homes, and cause health issues.

Because of this, many mattress makers have removed fiberglass as a material used in their beds. However, some mattress makers have decided to be deceptive instead of removing potentially dangerous materials from their beds.

Some mattress makers hide their fiberglass by saying it is just silica. Other mattress makers say they do not use fiberglass, but say it is a core-spun glass fiber yarn instead.

What’s the Deal with Fiberglass in Mattresses?

Fiberglass is excellent as a sturdy building material for light-weight applications. It is also a superior flame-retardant material that melts instead of igniting, smothering flames before they can ignite other flammable material. It has also replaced other flammable insulation materials like horse hair and straw used as insulation in the walls of homes.

The dangers of fiberglass in mattresses started to grow in popularity after a lawsuit filed in 2020 against Zinus, and its retailers, which stated the mattresses suffer from a defect that can cause fire-retardant glass fibers to be released. Interest in the topic was re-ignited in 2022 when a second lawsuit was filed against Zinus that claimed mattresses were defective for allowing fiberglass to escape into consumers’ homes.

So, What is Core-Spun Glass Fiber??

Core-spun composite fibers have a filament material encased by a sheath made of different kinds of fiber. Core-Spun fiber is a common material that includes sewing threads, yarns, and stretchy materials like spandex fibers. Here’s an artist rendering that shows the basic construction of a core-spun fiber:

Example drawing of core-spun glass fiber, fiberglass strands wrapped in a sheath of a different fiber.

Below is a photo showing an example of a core-spun fiber. It is a flame-retardant fabric with a core-spun aramid/kevlar yarn strand removed from the fabric weave. The yellow untwisted sheath of kevlar fibers exposes the fiberglass strands.

Photo of yellow aramid fabric with core spun fiberglass filament core yarn

Core-Spun Glass Fiber is just Fiberglass

It’s easy to see in the photo above that core-spun glass yarn is still just fiberglass beneath its outer layer. No matter how much the mattress makers try to say their glass fibers are different, encapsulated, or technologically advanced – it’s still just fiberglass.

Core-Spun Fiberglass Can Still Contaminate Your Home

Core-spun glass filament yarn might encapsulate the fiberglass and contain it better than bare fiberglass strands. However, once the spun outer sheath is compromised, the fiberglass core can break apart into smaller particles and move around the mattress.

Once loose fiberglass particles move around freely within a mattress, it’s almost inevitable that they will eventually escape into the surroundings. Fiberglass particles often get released just by poking through the cover fabric.

This fiberglass shedding happens even faster if the mattress sees rough usage like being jumped on, moved around a lot, and other *ahem* activities. If the bed has a washable top mattress cover, the glass particles can escape even faster while the top is off for cleaning.

It’s true that core-spun fiberglass may be a bit safer than loose particles, like the kind Zinus used. It’s probably better than the bare fiberglass fabric that was in most cheap mattresses until recently. However, it doesn’t lessen the dangers of fiberglass once the particles have contaminated the home. Sleeping on fiberglass can cause skin, eye, and even respiratory irritation – so why even risk it?

Mattress Brands that use “Core-Spun Glass Fiber”

Many big brands stand by their decision to keep using fiberglass even though it poses a major danger to the health of consumers. Here’s a list of the biggest brands still using fiberglass while trying to shift accountability by calling it core-spun glass fiber, core-spun yarn, glass filament yarn, and other variations of core-spun fiberglass.

  • Leesa – Leesa uses a core-spun glass, but it’s okay because, according to them, it’s like a pool noodle. Here’s what Leesa says about their flame-retardant glass material on its support page:

    “The glass is a portion of the FR thread and is completely encased within other thread components. To get a sense of what that means, imagine a pool noodle. The central empty space of the pool noodle is where the glass would be in the FR thread. The other thread components would be the outside ‘shell’ of the pool noodle.”

  • Puffy – Puffy uses a fiberglass core-spun yarn in its flame retardant mattress covers. Here’s what Puffy had to say in a FAQ page before access to the page was revoked:

    “Fiberglass is encapsulated in the core spun yarn of the required fire sock which is a flame retardant to protect the mattress, however, no fiberglass is bare or exposed, making this safe for use.”

  • Sealy – Sealy uses a core-spun glass fiber material for flammability testing. Here’s what Sealy said about fiberglass in an email reply to me:

    “The glass fibers in our mattress products are comprised of a core-spun technology that encases the glass in a flexible protective sheath housed within the internal mattress design, and is completely safe and inaccessible in normal use, even if the cover is removed.”

  • Tempur-Pedic – Tempur-Pedic is the sister company of Sealy, so its description of core-spun glass is exactly the same as the above reply from Sealy.

Mattress Brands that are Fiberglass-Free

To learn more about these brands check out my Big List of Mattress Brands without Fiberglass post here on FiberglassFree!

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Last Updated on February 16, 2024

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