sanding leaving dark marks

[Russ Peters]

Just out of curiosity does anyone else have a problem with the finer grits (500-1500) leaving behind black marks almost like filling in the grain?:mad::mad::mad: It has happened on the last two lighter colored pens that I have made. could it be not sanding enough on the lower grits?

[Charlie Schultz]

Are you using micromesh? It seems to me that if micromesh gets too hot (from the friction), it transfers from the cloth to the pen.

[Bonnie Campbell]

Are you sanding off onto the bushings too? It could be metal dust....

[Jim Underwood]

I have had the abrasive come off and embed itself in the wood when I've sanded Alder. I was using a white aluminum oxide 320 and all the grit shed into the pores. It's not as bad when sanding Cherry or Maple because they are harder and less porous.

[Ben Gastfriend]

It may be because you aren't sanding with the lower grits enough. On porous woods, you have to spend a little bit more time with the 150 to get all the pores pretty flush.

[Steve Mawson]

I have the same problem from time to time. For me I believe it got too hot in one spot.

[Bernie Weishapl]

Could be two things. One that was mentioned is metal dust if you are sanding over onto the bushings. The other more common is sanding with to much pressure which causes heat and will cause the problem.

[Brian Poor]

What are you using for paper?
Silicon oxide (black automotive paper) will tend to gum on some timbers if you are attempting to jump down to a super fine grit before the piece is ready for it.

[Nathan Hawkes]

I've been having the same problem when sanding Mulberry; I've been using the green craft supplies 2" discs on the intertial sander that they sell. I started with 80, then 100,120,150,180,220,320,400. Then wet sanded with 400,600,1200,then 1500 with BLO. If I push at all, the grit fills the pores. I have a habit of stopping between grits to "make sure" I've sanded enough, and didn't see any green until I finished with the 320 & 400 discs. I don't know if I'm pushing too hard or what, but the pores on the rim of one of the bowls I did are filled with green grit. After wet sanding, the pores were more or less filled with yellow fine grit, and made it look more or less natural. I gave away the piece, otherwise I'd post a pic. The pics I have don't show the grit in the pores at all. FWIW, I've started making my own discs to save $$ by spray-adhesive attatching the used discs to Norton 3X paper then cutting out the disc shape, and haven't had the problem since, but I have also been more careful about applying too much pressure. I also have found that some black wet/dry paper (don't remember the brand, but 400& 600 grit, if its been exposed to high temps--it was in the shed all last summer, seems to lose its "stick" to the paper & will come off when wet sanding. The gray-black micro-grit filled the pores & gave kind of a cool, or at least "acceptable" look, but definitely UNWANTED. So, I'm not using any old paper for sure. It seemed to happen between the 400-600 paper that the grit came off. HTH.

[Dennis Peacock]

Remember, when sanding, use lite pressure to allow the sandpaper to do the work so you don't have to. Also keep in mind that once you are above 600 grit? All you are doing is "polishing" and refining the scratch pattern until it's glass smooth...as you are no longer really "sanding". :D