The black 3M Wet/Dry sandpaper is great.  I use the 320, 400 and 600 grits.  I do not have the problem with it coming off on the wood.  I almost always sand to 600g.  Also, try not to apply too much pressure as it will often cause the problem you are speaking of when using cheaper abrasives.

Thanks for the quick replies.

I guess I haven't paid enough attention to the type of paper I've been using.  One more thing to learn!

I took a look at what I used:
100 garnet 3M
150 garnet 3M
220 garnet 3M
320 black "Gatorgrit", type unknown
400 black silicon carbide, no name.  Feels coarser than 3M 400
600 black, no name and 3M (not sure which one I used)

The new paper I bought is 3M "Sandblaster" 320 and 400 which are gold colored.  I used these after turning off the black residue from before.

Gil, I think you are right that maybe the cheap, no name paper could be the problem.  I can't tell which paper is for metal or wood/metal.  Most of the black papers say wet/dry.  It could be that just one of the papers I used caused the problem.  I'll have to experiment.

I found a source online called Supergrit, which sells 600 white, non loading, zinc stearate, silicon carbide paper, 100 sheets for $22.00, which would last me a lifetime.  I'll also check the sources you mentioned, Gil.

I just wish I could find a local source, as now my half saucer has to sit in the lathe until I can order the paper. 

Hello JR,

It may not be the sandpaper at all. I discovered early on that on some light colored woods I would get the same black spots. I finally traced it to a slight residue on my fingers from sharpening my gouges. The tiny particles of metal from sharpening would get on my fingers and leave these tell tale marks on the wood.

This may not be the case in your situation.... by it is another thing to look at.

Best wishes,
Dave

Ah...  actually it's not the 3M paper I'm using..it is the Norton that JimQ just mentioned.  Just looked... sorry about that mistake.

For shame, Negeltu, 30 rigatonis with a wet lash, or is that 30 lashes with wet farfala?  No, that's just a waste of good pasta. 

JimQ

hehe. 

In using the Norton sandpaper I've noticed I get better results using it if I soak it in water.  It really does seem to last longer.  I've also had good experiences with the 3M Sandblaster paper.

Thank you everybody for your input and warm welcome.

Sorry that I misquoted someone.  I have trouble remembering who gave what advice, so this time I took notes!

Negeltu and Gil:  On pressure and speed:  I think this may have been my biggest blunder.  I was sanding at high speed and the paper was getting pretty warm (hot!).  After I had skimmed off the black marks, I slowed the lathe way down in the 500 rpm range and resanded up to 400 grit with lighter pressure.  This was with the new 3M paper, so of course there were no black marks.  But I got a good finish, but still need to sand finer.

Dave:  It is possible that my scraper was not clean as I had not been too thorough with wiping it off after grinding.  I'll have to be more careful about that after this.

JimQ:  I haven't seen the Norton brand, only the 3M, at Lowes, Menards, and Ace Hardware.  Haven't checked Home Depot yet.

PhilipE: I'm about 40 miles west of Chicago, and there is a Woodcraft store 21 miles from here in (appropriately named) Woodridge, on Woodward Ave.  I just might have to take a road trip!

Thanks again everybody for the help.  I now know that I have to pay more attention to speed, pressure, quality of paper, and cleanliness of tools and hands.  Guess I was taking the sanding process for granted, but there's more to it, and probably still more to learn about it.