As an outdoorsy person (we’ll make that assumption, seeing as you’re reading this site!) you probably own one or more pieces of clothing which contain synthetic fleece. Invented in the late 1970s by Polartec, synthetic fleece – and it’s more modern brother the microfleece – is a fantastic fabric for keeping in warmth, fending off a bit of drizzle and letting out your sweat, and as such has been used by pretty much all outdoor manufacturers in some way.
The re-formulated Polar Proof from Nikwax is a wash-in waterproofer which protects fleece garments from picking up damp, wet mud and dirt by coating each fibre in a layer of secret-squirrel wax. OK, so synthetic fleece can be fairly water resistant already, but the Polar Proof ramps up this repellency and makes rain bead up and run off like it’s late for a date.
What’s noticeable about running a garment treated with Polar Proof under a tap is the lack of small drops which grab on to the pile, and of course the way that the stream of water flows off like it is being repelled somehow. I compared this to an older fleece garment which I own and the main difference is those small dots of water which stay on the fabric and in some places cause a wetting-out (where they sink in). You can see the little dots of water (they look white) on the untreated green fleece below.
So, Polar Proof does make a difference. I’d say it’ll be most effective in combating prolonged drizzle and the aforementioned dirty water splashes, which in turn should have maintain the insulating properties of the fleece itself and keep you warmer.
SUMMARY: Polar Proof is a wash-in waterproofer for fleece (and wool!) which helps stop water clinging to fibres and a garment wetting out. The difference is noticeable, but I’d still be wary to use a treated-fleece as an outer layer on a very wet day since it doesn’t add any form of windproofing.