Leo,

you wrote:
However I do not see a need to use more expensive water proof paper for
sanding bare wood, there are better and less costly abrasives for that,
and when sanding a finish on wood the loss of abrasive particles should
not be a problem.

I think dark red aluminium oxide waterproof is cost efficient on wet wood,
because:
- you can clean it in water when it clogs up and re-use it
- you can store it in a damp place, such as my little barn with very high
humidety (90%), without a loss of sanding ability
- only a fold will leave a red stain with high preasure in a tight spot
I agree its not cheap, so if you know a better way or cheaper sandpaper for
sanding wet and thin (2-4mm) wood, I'm very interested.

Dutchturner Chris