Burnishing wood

[Chris152]

Fiddling with a piece of wood on the lathe a while back I did this with the bevel of my roughing gouge.

I wondered what the effect of burnishing in this way is - could it create a finish that's sufficient by itself to resist moisture penetration in the way sanding sealer and paste wax might (if I've got that right)? When working with clay, burnishing the surface of leather-hard clay in this way creates a significant barrier (can't remember what you can expect it to resist, though) once fired. Or is it just a nice, polished-looking finish?
Thanks
Chris

 

[CHJ]

You are just bruising the wood by compression, give any exposure to moisture (even atmospheric) the fibres are likely to swell some way back to their original profile, suspect that the 'glossy' appearance will degrade in the process.

 

[williams1185]

watched a show on satellite many years ago two american guys they burnished all the wood used to make a cot and finished it with melted beeswax applied with a brush all they used to burnish the surface was a piece of chromed steel if i remember correctly they used a lot of pressure to burnish it apparently at the time it was the only child safe finish they would use think the prog was the furniture guys . ian

 

[Chris152]

You are just bruising the wood by compression, give any exposure to moisture (even atmospheric) the fibres are likely to swell some way back to their original profile, suspect that the 'glossy' appearance will degrade in the process.

The wood's been like that in the garage since February (I did this when I bought my gouge set but had no sharpening system, so was just playing around) and doesn't seem to have been affected at all by the cold and damp.

Is it possible that this 'bruising' could be a positive thing?

 

[Chris152]

Googling around I found this on a kitchen cabinet site(!):
'Burnishing is done by rubbing two pieces of wood together. The heat from the friction rubs away soft, dried cell walls and exposes the harder cells. These hard cell walls do not absorb stain or finishes, but they have a glossy sheen that makes finishing products unnecessary. Burnishing can also be done by rubbing small shavings or chips on the wood'
and elsewhere I read about the effect of heat on the wood, closing pores.

Maybe the only way to find out is to do some tests on water absorption on burnished / un-burnished bowls, but it was really just a matter of interest to see if a common practice with clay makes any sense carried over to wood.

 

[Phil Pascoe]

If you're thinking about moisture absorption I wouldn't trust sanding sealer and paste wax for more than a few minutes, anyway.

 

[Sheffield Tony]

We pole lathe turners quite often burnish by grabbing a handful of shavings and applying it to the rotating workpiece. On partly dried wood, you can get a nice silky smooth feel with just the tools and burnishing, sanding is not that good on wet wood.

I wouldn't expect it to afford water resistance though.

 

[Chris152]

Right, two recesses turned about 3mm into beech scraps, one sanded to 240 grit, the other sanded to the same and then burnished with the back of a roughing gouge (which got a bit scary) and then with a small block of oak (felt safer).

If you can contain your excitement, I'll post the results as soon as anything happens. Assuming something happens.

 

[Chris152]

Well, that's fairly conclusive. I can say with confidence that in the time it takes to go to the shop and buy a bottle of wine, the water in both recesses will have been fully absorbed.
Might try a more scientific method tomorrow.

 

[ED65]

When working with clay, burnishing the surface of leather-hard clay in this way creates a significant barrier (can't remember what you can expect it to resist, though) once fired.

Liquids. Biscuit-fired ware is like a sponge, but if you burnish the leather-hard clay to a good shine you create a much more closed surface that's at least somewhat waterproof without the need of glaze.

There is somewhat the same effect with wood. On burnished wood, with no finish at all applied, water will form tight beads on the surface but the surface is more water-repellent than waterproof as you've already discovered. And in case it's not obvious the harder and more close-grained the wood the better this works, since large pores and the bottom of grain lines don't get burnished.

If you want to delve into burnishing further Chris two historical things you might like to look into are boning and the polissoir.

Boning gets its name from having been done traditionally with an actual piece of bone, although the same basic technique can be done using a piece of smooth, hard wood or polished metal since all you're doing is compressing the surface wood fibres. Boning was once commonly done on baseball bats (still practised in some places) and used to be used as a final smoothing step on hammer handles and in bow making.

If you're intending to apply finish at the end I don't know that there's any benefit to burnishing, unless you keep at it long enough to scorch the wood and change its colour (which can simulate ebony if you take it far enough).