I recently did some wet sanding to improve the surface of some sycamore bowls that already had a Danish oil finish that had dried a bit rough. I used fine ‘wet or dry’ abrasive with white mineral spirit as lubricant and got some good results. After wiping clean, the surface was silky smooth. I applied some more finishing oil afterwards and they are now ready for buffing. Today I have been making some lignum vitae boxes out of old bowling balls. Lignum vitae is a very hard wood with a waxy content that clogs sandpaper like the dried oil finish on the sycamore bowls. I tried wet sanding here too, using water this time. I just held a wet bit of kitchen paper to the freshly turned surface at the same time as the abrasive. You could use a spray bottle. The result was lots of mud that sprayed off and made a mess of my turning jacket, but a very good surface was quickly achieved on the wood. No dust and no clogging. I started at 180 grit, then 240, and finally 320 which gave a fine matte surface ready for further treatment. It is important to use good quality abrasive, particularly if using ‘wet or dry’ silicon carbide paper. The cheap grades tend to shed particles and leave black specks embedded in the wood surface.
It was club night at my turning club last night. There was an interesting demo of making a spalted birch log into a hollow vase. The wood was very poor – I would have thrown it out – with advanced spalting and terrible tear-out. But the finished product was surprisingly good. The demonstrator used lots of quick-drying cellulose sanding sealer to harden the fibres before final turning to shape. Sanding with an unpowered rotary sander made lots of dust but left a quite reasonable surface.