The Axe is a Japanese inspired cloth face mask which can come in handy if you are chopping charcoal, playing ninja-and-seek, traveling, or navigating a worldwide crisis at the end-of-days. A well made cotton mask can be surprisingly effective at filtering out many unwanted materials in the air from pollen to charcoal dust.
The name comes from the similarity of the pattern shape to an axe (ono in Japanese). Aside from a cool style, three important interconnected aspects of an effective mask are a proper fit, filtering ability, and breath-ability.
- A proper shape, size, and fit ensures that air goes through the mask rather than leaking around the edges.
- A material or combination of materials that have the ability to block more particles decreases exposure for the wearer.
- A less restricted airflow allows the wearer to breath easier and wear the mask comfortably for longer.
For example, tea towels have filtering properties approaching surgical masks but have much more air resistance so t-shirt or pillowcase material is often recommended as the best trade-off between properties for this purpose.
Other materials used for the mask are hair elastics or rubber bands for the ear straps and a short piece of malleable aluminum wire to form over the nose area. Note that two straps that go around the head work much better to create a seal, especially at the chin. The design has an internal pocket which can optionally hold an additional layer of material such as a poly-fiber hvac allergen filter.
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Accurate fit is very important in order to get the maximum filtration value of the cloth in a mask. A pattern template is a starting point but making a prototype from scrap cloth or even paper is a good way to dial in the proper fit and size before making a mask. In terms of fit testing and seal, this pattern compares more to a surgical mask than a respirator design. This pattern uses a half template for the outside and a half template for the inside, two halves are cut from each to make one mask.
Testing has shown that tightly woven cotton can perform at more than half the effectiveness of an n95 filter, in the range of an ~n50-n70 equivalent. One of the best widely available materials is a sturdy cotton t-shirt fabric or high thread-count pillowcase, other possibilities might be quilter’s cotton, tight woven muslin, or old twill pants. The inner layer can be made from a thinner material such as tenugui or hankerchief to keep the airflow from being too restricted.
Pins should not be used to hold the fabric together in order to keep the fabric weave as tight as possible. Halves are joined together first, seams are ironed and topstitched down, then the edges of the inside (lining) fabric are folded and seamed.
Good side of the fabric should face inwards for the inside work stages. The front (self) and back (lining) are carefully aligned and joined together before turning right-side-out.
The mask is turned right-side-out by pulling it through one of the openings in the side of the pocket. A chopstick is used to ensure the fabric is fully opened around the edges. Ironing the edges flat prepares them for the next step of stitching around the outside edge. The width of the seam across the top must be large enough to fit the nose contour wire inside later.
Without a nose contour wire the mask will not seal very effectively. There are many options that could work, tin ties (from coffee bags), copper wire, pipe cleaner, heavy twist ties (but no paper for the wash), floral wire, folded strips of aluminum cans. Soft aluminum will not rust or poke through the cloth and is light and easy to bend. The wire shown below is 1.5-2.5mm (16-14awg) dead soft aluminum, edges filed or sanded round to remove sharp edges. Each time it is bent it will get harder by the process of workhardening so it should be left as-is until the wearer is ready to fit it to their face.
At this stage the careful testing of a prototype will pay off. The finished mask should end just before the ears so that a small elastic loop can provide enough tension for proper fit. Note that though ear elastics are easy to wear, two tight straps that go around the head work much better to create a seal, especially at the chin.
Several materials may be useful for the straps as long as they are not too wide and not too tight on the ears. Hair elastics or rubber bands should be about the right length to go through the folded clean finished seams at the ends of the mask. Head straps work better when they have some stretch, particularly the lower of the two.
For extra performance an appropriate filter material can be cut and placed inside the pocket of the mask. Some vacuum and hepa filters may contain glass fiber so careful research should be done before using a filter material for something other than the original intended purpose. There is a type of hvac ultra allergen furnace filter made from poly-fiber, of which some types are rated to capture very small particles (perhaps mpr 1500 or higher would be in the range of n80-n90). Bonded cellulose found in the form of certain brands of blue shop towels has also been tested to filter well in double layers.
Links & Information
Some recommendations for using a mask properly in a medical situation:
- To put on: Clean your hands with soap and water or hand sanitizer before touching the mask.
- Hold the mask by the ear loops and place a loop around each ear.
- Mold or pinch the nose contour wire to the shape of your nose.
- Pull the bottom of the mask over your mouth and chin and check the fit. Avoid touching the front of the mask while wearing.
- To remove: Clean your hands with soap and water or hand sanitizer before touching the mask.
- Consider the front of the mask contaminated. Only touch the ear loops.
- Hold both of the ear loops and gently lift and remove the mask to a safe resting location.
- Clean your hands again with soap and water or hand sanitizer.
Some further links that may help in the research and design process…
best recommended diy materials
do not wash charged synthetic filters
paper bag drying for 72 hours or more
growing collection of links to research and info
a very promising alternative mask pattern, info on filter testing with drc shop towels
fit tested quick mask (#2) using Halyard sterilization wrap
has some links and info on the use and effectiveness of masks
tea towel best filtering cotton material
better results when masks worn by the healthy rather than the sick within a home
reducing transfer within households
n95 mask composition
filtrete ultra allergen hvac filter msds