Sandpapers: Would appreciate some feed back and opinions please

[Steve_Karl]

There once was a time, and not very long ago, when all I knew about sand paper was that there was heavy, medium and fine
and it all looked like sand glued to paper.

Well now I think I'm seeing that not all papers, even of the same grit and by the same company (3M)
are the same and equal in the way they feel to the touch on my finger tips, and most likely in the way that they work on the wood surface.
(that's what I'd like opinions on)

Example:
400 Grit 3M Tri-M-ITE (Grey) feels less agressive than 3M Pro Grade Precision (Red) and both feel less agreessive than 3M Imperial WetOrDry Production Paper(Color = Black)
and even
600 Grit 3M Imperial WetOrDry Production Paper feels more agressive to me than 400 Grit Tri-M-ITE (Grey).
"Feel" is on left hand finger tip callus(plural).

I had the Imperial WetOrDry Production Paper in 400, 600, and 1200 left over from some painting I did on an old Chevy van 10 yrs. or more ago, and found it today when checking to see what I had on hand to finish up this body and the next one I'm planning on doing, wondering if I needed to get more paper.

I'm also curoius about the 3M Gold Free-Cut that StewMac seems to recommend and how it compares to the Tri-M-ITE and the Pro Grade Precision. Anyone using it and liking the results?

I know there's at least one sandpaper guru here, if not more.

Maybe someone can do an "Everything You Need To Know About Sanpaper" stickey?

I really think the 400 grit 3M Tri-M-ITE is less agressive and will do smoother work
(agree? disagree? call me crazy? . . . all input is welcome)
than the 400 grit 3M Pro Grade Precision (Red)
but the price difference between the 2 is a bit of a choking point isn't it?

 

[bagman67]

As a quick'n'dirty primer, Wikipedia provides some useful information.


https://en.wikipedia.org/wiki/Sandpaper


You'll get different cutting characteristics depending on the grit coarseness, the grit material and the coating - open coat leaves more space between the grit particles, which helps lessen the tendency for the paper to clog, especially when sanding woods with high resin content; whereas, closed-coat has more densely packed grit particles, which is more suitable to sanding a hardwood, metal, or finished surface. 


Some papers are also stearated, which means there is zinc stearate or calcium stearate as a component of the coating.  The stearate acts as a lubricant during wet sanding.  The general belief is that zinc stearate (and probably calcium stearate, opinions vary) is incompatible with water-borne finishes, as the lubricant interferes with bonding when subsequent coats are applied.
 
A brief round of research via das Google suggests that for hand-sanding unfinished wood, a coarser grade aluminum oxide paper is a good starting point for rapid removal of material, and then garnet in finer grits for subsequent rounds.  Once your finish is on, the wet/dry papers starting at 400 or 600 and up through the grits until you have the desired sheen are appropriate.


As with all things, nothing substitutes for empirical testing.  Your mileage may will vary, so you want to find out by how much.