Sorry about the delay in replying but it has been a hectic couple of weeks. I am not an expert on wood or burrs but I have turned a lot of them over the last few years so I have had plenty of experience. There are three main methods I use they are as follows:-
Sand Blasting
This is very effective but can be very messy so I built myself a sand blasting chamber from MDF with a sheet of Perspex for the front. You also need a good compressor with a large storage tank to make it easy, unfortunately I only have a small compressor so it takes a bit longer because I have to wait for it to recharge often. It works very well on thin barked burrs but you have to be careful you don’t do too much as you can easily mark and spoil the surface of the burr.
Pressure Washing
Again this can be very effective but also messy and you need a high power machine for it to be effective. Most machines found in the home don’t really have enough power to be very effective, mine included, so I use one at the local car wash when I want to do it this way.
By Hand
This is the most effective way, especially on thick bark burrs, but also the most time consuming. For this I use a selection of flat bladed screwdrivers, some 5/16” metal bars to rest the screwdrivers on for extra leverage, a hammer and some dental picks to get in the awkward places. Also a pair of thick gardening gloves and a full face shield because the burrs can be very sharp once the bark is off and pieces can fly all over the place when levering them off. The way I do it is to find a crack in the bark push the screwdriver in, sometimes with a light tap or two from the hammer then lever it off. The edge is a good place to start as once the burr is dry it usually cracks away from the wood. Once you are down to the wood in one place it then gets easier to continue as you can get the screwdriver in under the bark better.
I find it is easier to strip the bark once the burr is dry as on English woods the bark tends to break away from the wood when drying, but this is not always the case. There is no definite in this but I have found Chestnut the easiest to remove but even with that I still get some pieces that wont come off. In these cases I have found that if I put the burr out in the rain for a day or two then leave it for a few days to dry out sometimes the bark will come of then. Once the bark is removed you quite often get a discoloration on the surface of the wood this can sometimes be removed by either pressure washing or sand blasting.
Bark on English woods tends to be a lot thicker than on imports, I have been told this is due to our climate, and don’t respond very well to pressure washing so it is best to tackle these by hand. With Elm and Oak burrs I find that the bark is either going to fall off very easily or you just aren’t going to get it off. With burrs from down under I have found the best way to get rid off the bark is by pressure washing.
john