Thanks to Jon (an Eco House Group regular) who has written a summary of his experiences with eco-friendly paint. Jon says...
I used some Earthborn claypaint recently, and was pleasantly surprised. I was a bit sceptical about trying out a new type of paint, and it was expensive compared with standard emulsion. I was painting new gypsum plaster (board finish) with a certain amount of white polyfilla spots where imperfections had been smoothed over.
I started with a 'mist coat' of 4 parts paint to 1 part water, as per the directions on the tin. The opacity was something else - it covered all of the polyfilla perfectly, unlike a normal emulsion mist coat. After overnight drying, I started to apply a second coat. I did some of the room but after lunch, when the second coat was mostly dry, it was almost impossible to see the difference between the walls with one coat and those with two. At that point I decided not to finish the second coat and it's definitely not noticeable (a few other people have looked at it and agreed).
I reckon that if you can get away with one coat then it probably works out much cheaper than conventional emulsion, and certainly so if the cost of labour is included. I haven't worked out what coverage I acheived, but I did a fairly large room, including ceiling, with 5 litres (plus 1.25l water) for the first coat. The finish is very matt and the colour very nice.
Application is just the same as emulsion - brush and roller - and washing equipment is done in water and probably marginally more easily than emulsion. Also the paint doesn't seem to suffer from the same problem of drying onto the sides of the roller tray.
All in all, I'd recommend it and would use it again. It's not readily available over the counter locally as far as I know, but I have contacts in Bourne, Lincs and bought it from a family-run decorators supplier there called Stringers. It can be purchased mail order. The website is www.earthbornpaints.co.uk.