Dr Grau spent 18 months perfecting a “recipe” to convert recovered acrylic paint into new high quality paint in 14 colours.
She formed the company Circouleur in 2017 to start an industrial conversion process, and the first paints went on sale in Bordeaux DIY stores and to professionals last summer.
She said: “It has been very gratifying to see the reaction. We will be expanding into other DIY shops in the south-west and then, hopefully, across all of France.”
The paint left in tins in déchetteries has been separated out as part of the recycling industry for years, but until now it was sent away to be burnt, either in cement factories or in industrial incineration plants.
Now in the region around Bordeaux, tins that still have some liquid paint left, or thick paint under a skin, are sent instead to the Circouleur factory in the city’s suburbs.
There it is sorted by colour, filtered and then remixed with additives in a method developed and patented by Dr Grau.
The company produces 14 colours of interior paint, all chosen in consultation with a Paris-based design firm.
They are all muted tones, partly because of the difficulty of getting bright tones in the recycling process, and partly because the design studio advised that muted tones are coming into, and are likely to remain in, fashion. So far, the bestseller has been a shade of green called Eucalyptus.
Dr Grau was inspired to set up the company after decorating her own home and wondering what to do with the paint left in pots.
She investigated and was shocked to find it was destined for incineration, though a company in Quebec had been recycling paint for 10 years.
“I thought ‘you are a trained chemist and you should be able to use your knowledge to recycle this old paint’,” she said.
“For me, it made more sense to make new paint from old, rather than to try and mix colours and different thicknesses of old paint where the quality cannot be guaranteed.
“It was more complicated than I thought but I found a solution.”
She said she decided to recycle only acrylic paints, which use water as a solvent, because people were turning away from oil-based paints for environmental and health reasons.
“People now know that the strong new paint smell when oil paints are used is dangerous for health, as well as being unpleasant,” she said.
“All the trends in the market are for more acrylic paint to be used.”
The Nouvelle Aquitaine region awarded the firm a €68,000 grant to help it get established as part of its initiative to encourage recycling.
Prices of the tins of recycled paint are matched to those of existing brands – and the product is guaranteed like other paints.
“It is important to us that the use of recycled products is open to all, not just the well-off,”
said Dr Grau.
The environment agency ADEME estimates that 37,952 tonnes of paints, varnish and similar products were left unused by householders in France in 2017, based on the figure being 10% of the total amount sold.