HK Mask

The mask is indispensable for COVID-19 diffusion control. This time, we will show you how to make a cloth mask, how to put it on, and how to clean it, based on the "HK Mask" invented by Dr. K. Kwong, a Hong Kong chemist. Let's try to control the spread of COVID-19 by wearing HK mask of "high effect", "low material cost" and "easy to make".

1. What is HK Mask?

The HK mask is a reusable cloth mask with a disposable intermediate layer filter, invented by Dr. K. Kwong in the year 2020, during the COVID-19 outbreak.

The design of the HK mask is based on the design of a 3-layer surgical mask available on the market, which consists of an outer and inner fabric mask and an intermediate layer filter that goes between the two fabrics.

We use tissue paper and kitchen paper for the middle layer filter, so it will always stay clean. It can clean and sanitize the outer and inner layer cloths so that the mask can be used safely and with peace of mind.

Quote from HK Mask Official Site

2-1. Safety of HK mask Experimental results of the intermediate layer filter


An experiment on particulate filtration efficiency ("filtration efficiency") and respiration was conducted on February 20, 2020. (Dedicated nanofibers will be developed in the future.)

The figure on the left shows the experimental results of filtration efficiency and respiration. With only the outer and inner fabric, the filtration efficiency is as low as 8.70% and is very sensitive to particulates. Adding one sheet of tissue paper to the middle layer filter increases the filtration efficiency by 45.75%, two or three sheets, and reduces the impact of particulates.

As you increase the number of sheets of kitchen paper, the efficiency increases, but the PD flow rate exceeds 60%, making it difficult to breathe.

2-2. Supplementation of the intermediate layer filter

This section explains (0+45°) and (0+90°) shown in Figures 2-1.

Every paper has the characteristic of changing the flow (direction) of fibers in the length and width. By taking advantage of the characteristics of the paper, the filtration efficiency is adjusted.

Along with filtration efficiency, the ease of breathing also changes. For example, no matter how efficient the filtration is, like two sheets of kitchen paper, you can't use it every day if it doesn't breathe well.

Find the right middle layer filter for your daily use.

3. How to make a mask

The HK mask has a 10-minute video explaining the process from cutting to sewing. Please take a look at it once and proceed to the following process.

For details, please refer to How to make HK mask (movie).

3-1. Materials

Materials: one outer layer of cloth, one inner layer of cloth, one piece of wire, two elastic straps, and two cloth straps. (The video shows it in the HK Mask Kit, but it is not distributed in Japan.

The size of the cloth will vary depending on the pattern.

Please bring a chalk pen, tape measure, paper cutting scissors, cloth cutting scissors, thread cutting scissors, needlepoint, and needlepoint.

If you have a sewing machine at home, you will be able to work more efficiently.

3-2. How to choose a stencil

There are five free HK mask patterns for babies, children, teens, women, and men: XXS, XS, S, M, and L. From these, choose a pattern that matches the size of your user's face.

The pattern can be downloaded from here.

*On the left, I would like an image of a person's face facing right with a mask.

3-3. Explanation and preparation of the stencil

The stencil has an orientation, with the center of the mask on the right side of the stencil and the sides of the mask on the left side.

In addition, since a dimension of 10cm is drawn on the right end of the stencil, let's confirm that there is no mistake in the scale by measuring it with a tape measure.

The outermost solid line on the pattern shows the outer fabric of the mask, and the thick dotted line on the inside shows the pattern of the inner fabric of the mask. The thin dotted line is a guide to the seam.

Plain paper is sufficient for the pattern. Print out two sheets of paper and cut along the lines of the outer and inner surfaces, preparing one sheet of paper for each.

3-4. Determination

Fold both the outer and inner fabric in half so that the lining of the fabric is facing outward. Place the stencil on the dough and fasten the stencil with a needle. On the outside, after cutting the edges, make a notch in the area marked "notch hole". On the inside, the edges are cut and the cutting process is complete.

3-5. Sewing (1) The center of the mask of the outer cloth and the inner cloth

The cut fabric will be sewn together. First, sew the center of the mask. Sew the inside 1 cm of fabric. At this time, sew with the fabric cut (fabric lining facing outward). When you're done sewing, unroll the fabric.

*Image: Wrong Side (bottom) refers to the fabric lining.

3-6. Sewing (2) Upper part of outer layer cloth

Next, fold the top side of the fabric 1cm inwards (back side), with the lining of the fabric visible. Sew to the position of the first notch hole so as to secure the fold position. Next, insert the wire into the notch hole and sew the fold position to the edge.

3-7. Sewing (3) Lower part of outer layer cloth

Similarly, with the fabric lining visible, fold the underside of the fabric inward about 1 cm. Sewing to the edge so that this fold position is fixed, and the outer layer cloth sewing is complete.

3-8. Sewing (4) Top and bottom of the inner fabric

Next, the inner fabric is sewn. Fold the top and bottom of the fabric about 1 cm inward (back side), with the lining of the fabric facing up. Sew all the way to the edges to secure the fold position.

3-9. Sewing (5) Attaching elastic to the outer fabric

Rubberize both sides of the outer layer cloth, with the outer layer cloth surface visible. Mark the position of the rubber at the ELASTIC PLACEMENT position on the pattern. Fix the elastic in the position shown in the image and sew about 1 cm from the edge of the fabric.

*Image: The right side refers to the surface of the cloth.

3-10. Sewing (6) Sew the outer fabric and the inner fabric

Place both the outer and inner linings so that they face outward, and sew the ends together about 1 cm. Sew the elastic in place as it was earlier. After sewing together, cut off the excess at each end (about 0.5 cm). After cutting, return the cloth to the surface.

3-11. Sewing (7) Thread the string through both ends

Thread a string between the outer fabric and the inner fabric and secure it to the end. Sew from the top of the two pieces of cloth about 1 cm from the edge, so as not to sew the string.

3-12. Sewing (8) Finishing

Make a small rectangle at the bottom of the mask, about 1 cm wide, so that the middle layer filter does not fall out from under the mask. At this time, sew from the top of the two pieces of cloth. Next, sew both sides of the wire so that the wire at the top of the outer layer cloth does not slip out. Finally, tie both ends of the string that runs vertically through both ends to form a ball, and the HK mask is complete.

4. How to wear the mask

Prepare HK mask, alcohol disinfectant and a middle layer filter (tissue paper or kitchen paper). First, apply the alcohol rubbing solution to your hands evenly. Next, attach an intermediate layer filter between the two cloths of the mask. Then, put the elastic of the mask over your ears, and finally, tie a string around your neck and the back of your head to prevent the mask from falling off.

Please note that the installation manual is available in multiple languages.

Installation Manual (English)

Installation manual (multiple languages)

5. How to clean and maintain the mask

HK masks are rinsed with soap and water, without chemicals, without removing the middle layer filter. Rinse thoroughly with water and let it dry. After it dries, it's ironed and the cleaning is complete.

It is recommended that the HK mask should be replaced every 4 hours, either by changing the intermediate layer filter or by changing the HK mask itself, as is the case with general surgical masks.

Dr, K. Kwong

BSc (Hons), PhD (Chemistry) The University of Hong KongD., Department of Chemistry, Faculty of Science, The University of Hong Kong. A former lecturer at The Chinese University of Hong Kong, he is now also an authority on chemistry examinations. Also known as the Godfather of Chemistry, he has been producing high-achieving students over the years and breaking records for the number of students he has enrolled. He is the author of several best-selling chemistry textbooks, including "Longman, The Mastermind Series" and "Effective Chemistry" and "Quick Revision Chemistry.

Source :