Some maskers insert disposable filter materials (e.g. Filti) between the inner and outer layers of reusable cloth masks. For this reason, my Hybrid Mask has a filter opening! This offers the advantage of combining decent fit (through mask pattern) and filter efficiency (through disposable filters), but the disadvantage that filters are often complicated to insert, rarely cover the whole surface and easily slip. For me and my family, double masking, i.e. wearing FFP2 / KN95, surgical or self-stapled, same-pattern filter masks underneath, seems like a better option. Lately though, a lovely mask maker mentioned how complicated double masking is for kids, and I finally had an idea: Filter frames!
What is a Filter Frame and how does it work?
“Filter frame” means that top, bottom and sides of a mask are folded inside, so that pre-cut filter material can be placed directly on the very inside (instead of between inner and outer layer!) and therefore, the filter has full coverage and it is much easier to distribute into all corners and pleats. The inner frame holds the filters safely on all sides!
Depending on the pattern, you either fold the frame inside once, with an extra of min 2 cm / 0.8”, or twice, with an extra of min 4 cm / 1.6”. Pleated masks (e.g. Hybrid Pleated Mask) move along with the jaw and therefore, a double frame, where the filter sits not only inside the pleat, but also inside the folded-over part, which helps to hold the filter in place. Patterns without moving pleats (e.g. Hybrid Boxy Mask) have more stability, so a single frame is sufficient.
In the Hybrid Pleated Mask, the uppermost pleat segment is already folded inwards to form the reverse nose pleat, so that we do not need an additional segment for a secure hold. Therefore, we add just 2 cm at the top and 4 cm at the bottom. As the opening for the nose wire tunnel is part of the top seam, fabrics are shifted, so that the seam edge is 2 cm / 1.6” further down, and in order to keep the nose wire in place, we stitch under and also above it, in the ditch.
Making a Filter Frame for the Hybrid Pleated Mask
To sew your mask with a filter frame, enlarge the pattern: For the Hybrid Pleated Mask with nosewire tunnel, add 6 cm of length to the pattern and 3 cm of width to each channel strip (or simply download the PDF at the bottom of this post! :)). The dimensions in size M are 26 x 20 cm / 10.2” x 7.8” for the pattern and 8 x 10 cm / 3.2” x 4” for the strips.
After stitching the top and bottom seams as usual, 1 cm / 0.4” from the edges, press allowances towards the outer fabric, turn your piece right side out and move the fabric down 2 cm, so that 2 cm of inner fabric show on top of the outside and 2 cm of outer fabric show at the bottom of the inside. Press and pin / clip the edges, then stitch down the nose wire tunnel as usual, plus another seam up in the ditch, so the wire is held from both sides. Fold in 2 cm / 0.8” for the frame at the top, and then another 2 cm / 0.8” for the reverse nose pleat. At the bottom, also fold in 2 cm / 0.8” and then again, 2 cm / 0.8”, so that the front of your piece shows only the outer fabric, at about 16 cm / 6.2” height.
Now, you can continue pleating and sewing according to original instructions, until you get to the drawstring channels.
The first seam of the channel strips is sewn as usual, but after pressing the channels outwards, don’t fold the strips over 1 cm / 0.4” as usual, but so far that the edge of the strips meet the edge of the mask side. Then, fold tightly around the corner of the mask, so that the inner edge of the drawstring protrudes, and completes the frame on the side.
Using a Filter Frame with the Hybrid Pleated Mask
If your filter material is thin or flimsy, you can place a layer of heavy NWPP (70-80 gsm) on top, to keep it in place. If the pleats of the mask are opened before donning, the filter barely touches the face! If you nevertheless prefer natural materials for the innermost layer, you could sew envelopes for your filter material from thin cotton or silk.
To insert your pre-cut filters (you’ll find a pattern in the PDF!), turn the top and bottom edges of the mask with their double pleats inside out, insert the filter corners into the deep corners of the frame, then work your way down corner by corner, pleat by pleat, from top to bottom. When everything fits smoothly, fold in and flatten the frame!
The system works perfectly for my Hybrid Pleated Mask as well as my Hybrid Boxy Mask, so I assume it works just like a charm for other patterns too. If you try that, I’d be delighted to read comments about how it worked out :)
Depending on questions, I update parts of this post sometimes (last: December 6th, 2021). If you think that something is missing or unclear, please feel free comment below (or via Facebook, Twitter, Instagram) or send me an email!
Download of Instructions and Pattern as a printable PDF
Here you can download a printable PDF with the pattern for the Hybrid Mask with Filter Frames [V1 | Dec 4th 2021, 12:00] on 3 pages, in EU Din A4 or US letter format. Before download, make sure you’ve read the conditions below!
* Conditions of Use, Rights and Sharing
This design, pattern and instructions are protected by German copyright laws (© Iris Luckhaus | All rights reserved). I hereby agree to a non-commercial use of my design, which means that you may sew masks for yourself, your family and friends or for donating them to others for free, given that my copyright, name and website are always included!
Without my prior written permission, you may not reproduce, distribute or commercially use any of this material in any way. This means that you are not authorized to present this design (or modifications of it) as your own, and that you may not publish your own photo or video tutorials with my pattern! As long as it’s not a tutorial though, I enjoy seeing your pictures with my mask, and thank you very much for tagging @irisluckhaus and #luckhausmask! :)
For updates and further developments (which are sure to come!), please follow me on Facebook, Twitter, Instagram, Xing, LinkedIn, Pinterest or YouTube. If you’d like to share my pattern with your friends, feel free to use my posts!
I’m spending a lot of unpaid time on elaborating and explaining those instructions, helping the helpers to help. If you’d like to encourage this, I’d highly appreciate if you could buy me a little time via Paypal (firstname.lastname@example.org)!
If you’d like to use my instructions commercially (i.e. with the intention of making a profit), f.e. by selling masks sewn according to my pattern, please contact me and let me know more about your business, your location and your ideas!
Great thanks to Kimberly for that filter discussion which – finally – inspired this idea! Furthermore, as always I’d like to thank the countless volunteer sewists from various mask groups on Facebook, especially Rebecca, Hope, Jocelyn, Ania, Devon and Sophie, to whom I owe a large part of my mask education! You guys are all absolutely amazing.
Take good care of yourself and stay well! ❤