Last week I purchased a packet of "Thermilate" insulating paint additive. This cost AU$43.64 from The Natural Pain Place in Newton Sydney. The packet holds about one litre of white power and is intended to be added to four litres of paint. The power consists of what are claimed to be small hollow ceramic spheres, which contain a partial vacuum and therefore have a high insulation value. The effectiveness of this material for insulation has been called into question, but my intention was to try using the reflective properties of the material for a projection screen painted onto a wall. This was after the failure of my attempt using White Knight "Reflect-All" light reflective paint.
However, Christmas intervened before I could try the paint as a screen. I had far more of the paint additive than needed for tests. There was a small concrete deck to be painted before a Christmas party, and the additive was gritty, so I used some of it as a non-slip additive for the deck paint.
The material has a chalky texture and I was worried it would not mix well with the oil based heavy duty deck paint I was using. But it mixed in easily. The resulting paint was of a different consistency with the grit clearly visible in the paint.
The paint when on well using an ordinary roller. However, when it dried there were white chalky streaks visible in the high gloss dark green paint, showing the individual roller marks. Also the paint was a noticeably lighter colour that the original. The paint also had a slight white sheen, which was not really wanted for a deck, but indicates it may work well for a projections screen.
I found that by using a cross hatch pattern with the roller for a second coat, I was able to get an acceptable finish with the paint. The white chalky patches were still visible, but broken up in a random pattern were aesthetically pleasing on the slightly rough finish of the concrete deck. Glossy dark green paint must be about the hardest to hide the white additive in and, if used with typical a semi-mat off white paint, the additive should not be visible.
The additive provided a very good non-slip surface and is comparable in price to the grit additives sold for paint. The surface felt less cold than untreated paint on the same concrete, suggesting that the additive has some insulating effect.
The insulation claims for the material appear excessive and not credible. However, tere have been some independent tests which suggest some value for the material. Assuming the packet contains 1 litre of power, dispersed in 4 litres of paint this would cover about 10 square metres of wall (assuming two coats), forming a layer about 0.1 mm thick. The spheres would have to have exceptional insulating properties for a layer this thin to have a insulating value comparable to conventional insulation, which is hundreds of times thicker.
However, in situations where no conventional insulation can be installed, the paint may have some value, as discussed in Paul Teather's 2004 thesis: "A study of Ceramic Microsphere Insulation with a consideration of the wider implications". Applying insulation is a complex business, whereas adding the powder to paint is not. As an example if there is an uninsulated solid brick or concrete wall, any insulation would be better than none. However, it is not clear if this additive is much more effective than just a thicker layer of paint.