"Chris van Aar" wrote in message
t.nl...
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.


Chris, are you referring to aluminum oxide paper (or cloth) with red resin
adhesive? From your description of breaking the adhesive by folding, I
think you might be.

A German sandpaper manufacturer, Klingspor, makes a gold-colored
cloth-backed paper with good moisture resistance in grits down to P400,
though it is not designated as wet/dry. I have used it to wet sand finishes
when I felt too lazy to go downstairs after the SiC paper.

Wet/dry SiC (black) papers, as people have told you, are designed to be used
on non-porous materials, where the relatively weak adhesive merely creates a
sharpening slurry when it sheds grit. Sort of like rubbing with pumice.
If the grit embeds itself in the soft area of a spalted piece or an
open-pored area in light wood, a shadow remains. You might choose to use
pumice instead of sandpaper, as well. It becomes transparent when embedded
in the finish.