not too sure but here's an article i found that might help:
"A shaving brush isn’t just a paint brush for your face. A good brush – and the best brushes are made of badger hair and start at $25 – absorbs hot water and then, after you dip the tip of the brush into your tub (yes, not a can, but a tub – I’ll explain later) the brush releases and mixes the hot water with the shaving cream as you skim the brush back and forth across your face and neck in and up-down motion. The combination of hot water mixing with the cream and getting beaten by the brush all over your face delivers a thicker, richer, more emollient lather that’s impossible to get with your fingers alone. A shaving brush also gently exfoliates, or removes the dead skin, from your face before shaving, which gets rid of anything coming between the blade and your whiskers. Finally, the up-down brushing lifts your whiskers and suspends them standing upright in the thick lather, which exposes the maximum whisker length to your blade as it skims along your face.
Genuine badger hair shaving brushes come in all sizes and hair types, costing anywhere from $25 for a basic pure-grade badger model to $550 for a monster-sized, high-end English hand-made job containing only the hair from the badger’s neck, which is said by some (though not by me) to be the finest and most rarefied expression of water-holding bristle known to man or badger.
Do you need a $550 shaving brush? Unless you’re Mr. Burns, the answer is no.
I’ve gone through a lot of shaving brushes over the years, and as long as you stick with a genuine badger hair brush (cheaper brushes often use boar’s hair, which is much stiffer and pricklier than badger, and not nearly as comfortable on your face), the only things that matter are size and price. Bigger brushes hold more water and tend to make better lather faster and more easily, but really, the difference in lathering between a small $25 badger brush and that crazy $550 giant is negligible as long as you know what you’re doing, which means that if you can soak a brush in a sink full of hot water for a second or two, dab some shaving cream on the tips, and then swipe it up and down on your face and neck till you work up a thick, opaque layer of lather, you know what you’re doing. I recommend the English-made Vulfix brushes, which are much more reasonably priced than a lot of high-end British shaving brushes which don’t begin to approach the quality of the Vulfix models. They’re easily the best shaving brushes I’ve come across, despite being the most reasonably priced."
Source:
http://www.msnbc.msn.com/id/6886845/
