News / Covid-19

Venessa van der Westhuizen
4 minute read
6 May 2020
11:05 am

Safety standards to follow when making cloth masks

Venessa van der Westhuizen

To sterilise a mask, it must be ironed at a high temperature.

Picture: Supplied

There are already a few much-appreciated groups in Potchefstroom that are diligently making cloth masks for essential workers and the elderly. All the effort means nothing, however, if the masks don’t adhere to the necessary safety standards.

The Herald approached a lecturer in Consumer Sciences at the NWU, Louise Wyma, to determine the basic standards of protective masks. She and her students are working on a production line to make masks, which they also donate to essential workers. Speaking from a consumer science and textile perspective the type of material used is critical.

Why is woven cotton recommended when making cloth masks?

Cotton is a cellulose fibre with the best characteristics for cloth masks. It has good absorbency, which makes it comfortable for warm weather.

Cotton fibres absorb more moisture and feel good against the skin in high humidity, since moisture passes freely through the fabric, thus aiding evaporation and cooling. When used in a mask, it will take longer to get wet than synthetic fibre, since moisture from breathing will evaporate.

Cotton can also withstand high temperatures, enabling it to be sterilised by pressing with a hot iron. It has low resiliency, which causes it to wrinkle badly, except when treated. This is one way of recognising cotton. It is a good conductor of heat, which prevents static build-up. It is flammable, ignites quickly, burns freely with an afterglow and grey feathery ash, and smells like burning paper, an easy way to identify cotton fabric.

Louise suggests the following when making or buying a cloth face mask:

  • Cloth masks should fit snugly.
  • Include multiple fabric layers, of which the outer and inner are cotton woven fabric in two different colours or patterns. This enables the user to differentiate between the inside and outside.
  • An inner made of non-woven, breathable laminate fabric, like spun-bond, should be used on the inside. You may also use a dried-out wet wipe or a tissue as a filter but be aware that tissue may get soggy after a while.
  • Allow for breathing without restriction.
  • The masks should be able to be laundered in warm soapy water and machine dried without damage or change of shape. It should withstand warm iron temperatures to sanitise before use.

A snugly fit calico (weaved cotton) face mask. A mask must be washed and ironed at a high temperature every day.

To sterilise a mask, it must be ironed at a high temperature. Other materials like polyester and olefin will not be able to withstand the high heat. Cotton is, therefore, more suitable for a mask. A more comfortable cloth mask would be made from 100% woven cotton (not knitted cotton, like T-shirt material) with a pocket to insert a spun-bond removable filter. The filter should be similar to what is used in surgical masks. Since the mask has to be washed and ironed after each use, however, the filter should be removable, as spun-bond will not withstand the heat and washing process.

A spun-bond filter is put between the double layer face mask. It must be removed when you sterilise the mask by washing it in warm soapy water and ironing it at a high temperature.

What is the difference between woven, knit and non-woven fabric?

Woven fabrics are made with two or more sets of interlaced yarns at tight angles. This makes woven fabrics relatively stable, with little stretch, less air, and water permeable. Examples are denim and calico.

Knitted fabric uses needles to form a series of interlocking loops from one or more sets of yarn. Knit fabric is mobile and elastic with open spaces between yarns that let wind and moisture penetrate. This fabric is less stable, porous and more susceptible to shrinkage. Examples are jersey knit and T-shirting.

What is thread count?

The density of fabric or the number of yarns in a square centimetre of the fabric. A higher thread count indicates a higher quality fabric with better strength. Woven cotton has a high thread count and is denser than knitted cotton.

What is spun-bond?

This fabric is made by continuous hot filaments laid down in random order and fused together at cross points. Spun-bond is durable, lightweight with good air permeability which works great as a filter. It is for example used for medical protective apparel.

Spun-bond is durable and lightweight with good air permeability.

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