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Fusible Interfacing for Face Masks: Good Filter? Safe? Breathable?

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Today I’m investigating if you can use fusible interfacing in your face mask. Is it a good filter? Is it breathable and safe? Is it washable? And what type of fusible interfacing should you buy?

I’ll also suggest sew-in interfacings if you want to avoid glue.

I am only using data from credible lab studies and interfacing manufacturers like Pellon and Vilene/Vlieseline.

Overall, technically you can use fusible interfacing in face masks. It will provide some filtration (to block out particles) and it’s breathable.

However, the safety of the glue is unknown. We don’t know what chemicals are used in the glue and whether or not they’re toxic.

I have only seen 1 manufacturer discuss this. A customer service representative for Pellon said: “our fusible coatings are all non-toxic and acid-free.”

Best interfacing for face masks:

Manufacturer Vilene/Vlieseline recommends 4 of their interfacings for masks. However, they accept no liability.

I recommend buying a light or medium weight type for easier breathing.

Here’s where you can buy them on Amazon (these are affiliate links):

A customer service representative for Pellon suggested some Pellon interfacings.

These products have not been “specifically tested as surgical grade”, however.

  • 905 sew-in lightweight
  • 910 sew-in featherweight
  • 930 sew-in midweight
  • 40 midweight stabilizer
  • 360 E-Z stitch
  • 380 soft-n-stay
  • 915 cambric
interfacing for face masks

What is fusible interfacing?

In case you’re wondering, fusible interfacing is a material used to strengthen and stabilize fabrics.

One side has glue dots on it. This allows the fusible interfacing to attach itself to fabric.

Fusible interfacing can be made from many fibers, however, Polyester is the most common.

You can get woven, non-woven, and knitted types of fusible interfacing. Plus different weights.

Contents list:

Related article: 20 DIY Face Mask FILTER Materials Tested & Compared (Study: April 2020)

Related article: Sew-In Interfacing VS Fusible – Which is Better?

Related article: How to Use Fusible Interfacing Correctly (Apply & Prewash)


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Is fusible interfacing a good mask filter?

black fusible interfacing with white glue dots

Particle-testing company TSI and fashion designer Chloe Schempf decided to find out.

Schempf sent the company samples of popular filter materials.

TSI tested them using the same machine and test procedure used to give N95 masks their NIOSH certification.

Schempf told me this is a more accurate way to test the materials:

Many universities and labs are giving results that are not totally accurate – a spectrometer or a laser particle tester are not the best instruments for this testing and TSI filtration engineers have given me some very good info why this is – but I haven’t had a chance to add this to the site in a less technical form.”

C. Schempf via email correspondance on 8 May 2020.

Their study tested 1 type of fusible interfacing:

  • It was fusible, which means it had glue on it that melts and sticks to the fabric it’s stabilizing.
  • It’s medium weight.
  • It’s non-woven.
  • It’s made by the brand Pellon.
  • It’s most likely made from 100% polyester (based on Pellons product description for interfacing that meets the above criteria. However, I can’t be sure that it’s the exact product the study used).

The lab results:

pellon interfacing for face masks
Please note, this may not be the exact product used in the study.
% efficiency% penetration
2 layer Pellon Medium Weight Fusible Interfacing17.2482.76

They tested how well 2 layers of Pellon medium weight fusible interfacing captured particles.

The results weren’t amazing.

The 2 layers captured 17.24% of particles. So it’s better than nothing. However, it let 82.76% of particles through the material.

If you combined it with 2 layers of quilting cotton it would capture slightly more.

You could do this by making a 2-layer face mask from cotton and then inserting 2 layers of interfacing inside.

How this compares to other face mask filter materials:

Here’s an article where 20 face mask filters were tested and compared. The results are explained in an easy to understand way. And I talk about the safety of popular filter materials: some materials are risky!

Here’s the full set of results from the TSI/Schempf study. They have tested a lot of materials!


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Is fusible interfacing breathable?

Yes.

The TSI study tested 2 layers of medium weight fusible interfacing.

It was one of the easiest materials to breathe through in the study, with a pressure drop of 1.08 mm H20.

Wait, what’s that?

mm H20 is a way to measure a material’s resistance to airflow, aka. “pressure drop”.

The higher the number, the harder the material is to breathe through.

For comparison, a typical N95 mask has a pressure drop of about 9 mm H20. The maximum that NIOSH will allow an N95 to reach is 35mm H20.

“If the pressure exceeds 15 mm H20 you start to gain a vacuum effect and essentially start to suck air from the sides of your mask losing the benefits of the mask. It will also be uncomfortable and hard to breathe.”

C. Schempf (2020). Source: https://www.maskfaq.com/test-results [accessed: 7 May 2020]

So the 1.08 mm H20 from fusible interfacing is very breathable in comparison.

I tested this myself.

I held up 2 layers of lightweight, knitted fusible interfacing to my nose. I could easily breathe through it.

I did the same with 2 layers of lightweight, non-woven fusible interfacing. Again, it was easy to breathe. 4 layers were harder to breathe through, but still doable.


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Is fusible interfacing safe to breathe through?

fusible interfacing close up

What interfacing manufacturers think:

I checked interfacing manufacturer’s websites.

I can’t find any information from Pellon.

*8 August 2020 update*: a reader showed me their emails with a customer service representative from Pellon.

The Pellon employee said, “our fusible coatings are all non-toxic and acid-free.”

Vlieseline/Vilene have also made a statement:

“As a leading manufacturer of interfacings we have been contacted about the best products [for face masks] and we wanted to offer some support with these requests.

After various test our sewing samples have shown that the products M12, L11, S13 & F220 are… best suited for the construction of a simple mouth guard.

However, we must be clear the products listed are for sewing into garments.

Therefore we cannot guarantee the suitability for use in a respiratory protection mask with direct contact to the skin and moisturized by breathing air – and accept no liability.

Our non woven materials are neither virucidal nor tested for their filtration properties in the medical device sector.”

Vlieseline Freudenberg UK via their Facebook page. Source: https://www.facebook.com/VlieselineFreudenbergUK/photos/a.1921419511478003/2698823110404302/?type=1&theater [published: 6 April 2020]

Their products are not designed for face mask purposes, so understandably, they have not been tested for this.

Is the glue toxic?

The open source project Created for Crisis mentioned some potential risks with fusible interfacing:

“Fusible interfacing contains a heat-activated adhesive, which can interfere with breathability.

Our primary concern, however, is toxicity.

Not all materials are safe to breathe through for an extended period.

Because information about which adhesives are used is proprietary, we don’t know what chemicals we’re dealing with.

Until a thorough investigation of heat-activated adhesives is conducted, we cannot recommend any fusible interfacing.”

Created for Crisis, https://www.createdforcrisis.org/projects/masks/faq/ [accessed: 29 June 2020]

*8 August 2020 update*: a reader showed me their emails with a customer service representative from Pellon.

The Pellon employee said, “our fusible coatings are all non-toxic and acid-free.”


Is fusible interfacing washable or reusable?

washable fusible interfacing
Wash and tumble dry signs on my fusible interfacing.

Yes, once attached to fabric, you can often machine wash and tumble dry it.

Check the selvage edge of your interfacing for the wash and dry clean signs (pictured above).


What type of fusible interfacing should you buy?

Vilene interfacing for face masks
The floral face mask is made using the fusible F220 from Vilene. The yellow face mask uses M12. Source: Vlieseline’s facebook page & Empress Mills.

You can get many different types of fusible interfacing. Here are the main ways they differ: by fiber, weight, and weave.

FibreWeightWeave
PolyesterLightWoven
BlendsMediumNon-woven
HeavyKnitted (stretchy)

Vilene

Vilene/Vlieseline recommends their M12, L11, S13, and F220 for face masks.

Only the F220 is a fusible type. The others are non-fusible sew-in’s.

Here’s where you can buy them on Amazon (these are affiliate links):

Pellon

The study mentioned above used a non-woven, medium weight type by Pellon. I believe it was the polyester Pellon 931TD (because it matches their description), but I cannot be sure.

*8 August 2020 update*:

A reader showed me their emails with a customer service representative from Pellon.

The Pellon employee said, “our fusible coatings are all non-toxic and acid-free.”

She also suggested some Pellon interfacings.

These products have not been “specifically tested as surgical grade”, however.

  • 905 sew-in lightweight
  • 910 sew-in featherweight
  • 930 sew-in midweight
  • 40 midweight stabilizer
  • 360 E-Z stitch
  • 380 soft-n-stay
  • 915 cambric


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