Official Luthiers Forum!

There was a discussion of sandpaper and more than one person stated they did not use aluminum oxide because it left some of itself behind on the wood.
Could someone please explain this?

If not aluminum oxide, what?

Thanks guys,

while we're on it, someone might discsuss stearated vs. non-stearated. Not to hijack, just to piggyback

not to highjack either but a quick reminder of the American and European grading systems might be in order. I mention this in my finishing DVD. If the paper is P grade paper than it is coarser than the American grading system. The numbers could be the same i.e. 1000 grit in the P grading system is actually around 500 grit in the American system. If you mix the two systems you could end up putting scratches back into the surface instead of removing them.   

aha. Just ran into that I think. I'll check for the "P". 3M (I think) 8oo grit automotive was coarser or least more agressive than some 600 I had around. Annoying.

And now back to Bob's original question. Is it a stearate residue? only affecting water based finished? Help Us Please!

P-grit stuff is coarser, but it's got a more even grain size than CAMI grade stuff, IIRC.

Do not use stearated sandpaper on your guitars it leaves behind deposites that will give fish eyes to any stain or finish you apply later. Sand paper is one thing I do not skimp on. Do not buy the junk in the hardware store. The 3M you get at Lowes is a lot different than the industrial grades you can get at Fastenal and other industrial supply companies.

For basic sanding in 80,120,220,300 grits I use Klingspor products. For finish sanding in the 400,600,800,1000 and 2000 grits I use the 3M sanding films that you can get from LMI and Stuart Mac. For sanding belts and Drums I get the good Klingspor products as well. It is consistant from sheet to sheet and you end up using less of it so it saves money in the long run.

[QUOTE=mrpbody44] The 3M you get at Lowes is a lot different than the industrial grades you can get at Fastenal and other industrial supply companies.[/QUOTE]

Do you mean within the 3M line? Does 3M have an industrial line?

I use micromesh for 1,500 and up

I agree about not skimping! Klingspor has a good rep too. Consistent scratch is critical!

[QUOTE=mrpbody44] Do not use stearated sandpaper on your guitars it leaves behind deposites that will give fish eyes to any stain or finish you apply later. /QUOTE]

That's odd because I use Grizzly sterated papers (220 & 320) between coats (of Nitro & Catalyzed Urethane) and I have never had any fish eye problems (except Bubinga which is another nightmare story).

Sterates can cause problems on waterbornes but a quick wipe down with Naptha and a clean cloth will remove the sterates. Never a problem on KTM9 or Target 9000 either after wiping with Naptha.

_________________
tim...
http://www.mcknightguitars.com

Stearates are not a problem for shellac or nitro lacquer (the only finishes I
use). In fact, stearates are what is added to lacquer based sanding sealer to
make it sand well.

_________________
Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

I've always used standard aluminium oxide papers with no problems. I always wipe down with a tac rag then naptha and my final finish is always with shagreen and scraper.

I always FP so that might make a difference.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

What is the PURPOSE of stearates in sandpaper? non loading?

Sterrates are a dry lubricant and they also reduce finish loading of the sandpaper. Like Howard said, if you stir lacquer sanding sealer you will notice the white milky stuff - that's the sterates which are in suspension.

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tim...
http://www.mcknightguitars.com

Thanks, that's what I thought, but didn't know the "solids" in sealer were stearates. But since sealer sands so easily, it makes sense. Thanks Tim.

BTW, I usually wet sand through from 400-whatever is the highest grit in my micro-mesh sanding cloths

BOB -did any of the previous posts answer your question?

Terry: I should have added that not all of the white milky stuff is sterates. They also add more solids to the sealer as well.

_________________
tim...
http://www.mcknightguitars.com

Thanks much guys