A group of high school pupils, a retired railroader and three second world war veterans have created a self-sanitising varnish.

A group of high school pupils, a retired railroader and three second world war veterans have created a self-sanitising varnish.

They found that adding cetavlon, a common ingredient in shampoo, to paints and varnishes created self-sanitising surfaces that killed germs for months and presented this finding at the 105th general meeting of the American Society for Microbiology, in Atlanta, US, today. 

Before making this discovery, the team of students tested different metal dusts, salts and organic chemicals in clear, alkyl-based durable varnish to see how quickly they killed the microbes applied to them. Colloidal silver, well known for its antimicrobial properties, was the most effective self-steriliser but its high cost is prohibitive. 

Varnishes made with 25 per cent copper I and II chlorides self-sterilised within seconds but the copper salts added colour to the coating. Quarternary ammonium salts at a two per cent concentration also self-sterilised in seconds and did not discolour the varnish. Metals aluminium, iron, nickel, tin and zinc and their salts took longer to kill bacteria. 

The varnish containing cetavlon was the clear winner: it killed microbes within seconds of their application to the surface and could be used in much lower concentrations than the copper chlorides. In addition, the shampoo ingredient is proven safe for human use and the coating was still active five months after application and still self-sterilising within 30 seconds. Detergent cetavlon was especially effective because it has good dopant properties, the researchers said.

Although the team, which collaborated through the website www.science-projects.com, made self-sanitising paints and varnishes it hasn’t been able to do the same for floor and furniture polishes.

Carl Vermeulen is a retired microbiologist who runs the science-projects website. ’Public buildings, and especially schools, are at the centre of the epidemiological web for spreading common upper respiratory diseases that cost the US hundreds of billions of dollars annually in lost productivity. While it has long been know that our coinage possesses the quality of being self-sterilising, little thought has been given to making frequently handled surfaces such as railings, doorknobs, push-plates, desktops, and faucet [tap] handles in public buildings similarly self-sterilising through the addition of rapidly effective agents,’ he said.

Fiona Salvage