Is it just my imagination or is my 'Kingspore' brand waterproof sand paper
leaving black marks on some of my work? Ok, I know you can't see it!
However, I've been working with white birch and it sure looks like it's
darker in spots after I've sanded it, both dry and with a blo/thinner mix.

How does the 'dark red aluminium oxide' waterproof paper perform and will it
leave a stain?

--
Tom in Qualicum Beach, BC

"Tom Storey" wrote in message
news:Lj4nf.95140$Gd6.22530@pd7tw3no...
Is it just my imagination or is my 'Kingspore' brand waterproof sand paper
leaving black marks on some of my work? Ok, I know you can't see it!
However, I've been working with white birch and it sure looks like it's
darker in spots after I've sanded it, both dry and with a blo/thinner mix.

How does the 'dark red aluminium oxide' waterproof paper perform and will
it leave a stain?

Silicon Carbide (SiC) grit doesn't fracture like aluminum oxide, which is
why it abrades as full grit from the glue into the raw wood sometimes Plus,
it's normally mounted on thin paper, where creasing and flexing knock off
even more. That's why I don't use it on raw wood. Once you have some finish
between the paper and the pores it's easier to wash off the mix of cellulose
and grit with a bit of solvent.

You can use the Klingspor gold cloth-backed stuff wet, so I'm told. I've
never given it more than a few brief tries, but it seemed to hold and not
color. Haven't encountered any red wet/dry, but if it had a more flexible
backing, it would seem a better choice. Aluminum oxide is almost colorless
in the mineral.

Tom.
I am curious where the dark spots are. I have noticed that sometimes
the end grain will finish out a different color than the flat grain. I
have also had black spots show up on wood that is reaction from the
powder left on my gouges from sharpening. If your wood is dry, it won't
show up at first, but does after a while.
robo hippy

There doesn't seem to be any one area that attracts the stain, I just notice
a slight darkening here and there that I don't get it when I use 'normal'
sand paper. The birch I'm using is quite spalted and soft in spots and it
could be that some of the stain is from the spalting? I seem to get less
staining when I apply diluted shelec as a sanding sealer before sanding. The
following is a sample of what I'm dealing with. The tear-out is more evident
in the picture than it is in real time.
http://tinypic.com/view/?pic=igloi8

"robo hippy" wrote in message
ps.com...
Tom.
I am curious where the dark spots are. I have noticed that sometimes
the end grain will finish out a different color than the flat grain. I
have also had black spots show up on wood that is reaction from the
powder left on my gouges from sharpening. If your wood is dry, it won't
show up at first, but does after a while.
robo hippy

Hi Tom

The water proof sandpaper is not designed for the rough treatment of
sanding bare wood, but rather for the sanding of automotive finishes and
other more delicate final finish treatments IMO.

And yes the abrasives will be ripped off of the paper backing in
imbedded into the wood, and in light color wood you can get enough of
that to be visible, other people have also reported this.

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.

Have fun and take care
Leo Van Der Loo

Tom Storey wrote:

Is it just my imagination or is my 'Kingspore' brand waterproof sand paper
leaving black marks on some of my work? Ok, I know you can't see it!
However, I've been working with white birch and it sure looks like it's
darker in spots after I've sanded it, both dry and with a blo/thinner mix.

How does the 'dark red aluminium oxide' waterproof paper perform and will it
leave a stain?