radius sanding blocks - fb edge sanding through.

[swarfrat]

I acrylic coated my fingerboard, and during the sanding phase I keep getting stripes of wood down the edges of the fingerboard.
I'm not sure if this is 1) my radius block, 2) technique, or 3) maybe my sandpaper buckling from being held on the sides. I'm thinking maybe #3.

It sands through leaving a raw wood stripe. My fingerboard is a 10" straight radius (fretless), and I have a 10" radius block and I measured it with gauges - it's 10", not 9.5 or 12. 
The side is visible but can't be felt - so it's less than 0.001" low. Since it's so slight - I'm wondering if the best thing to do is to just take the whole fingerboard down to bare wood. It's visibly rougher (like 400 grit) than the surface finish of the board, and lighter in color where I sanded through (ebony). Also I'm getting ebony sawdust, so I know it's gone through. They didn't go away when I reapplied finish.

Anyone know what I'm doing wrong?

 

[bagman67]

Well, acrylic-coating an ebony or other exotic hardwood fingerboard is usually not done, and most folks would recommend against it because, well, most of the time nobody does it.  But leaving that aside - if you decide to just sand the fingerboard bare, you will be fine. There are 300-year-old violins and cellos being played that have the same ebony fingerboards they had installed on the original craftsman's workbench.  A little mineral or other very light oil from time to time will keep yours from drying out, if that's a concern; but if you play pretty frequently and play all over the neck, your own finger grease will likely do the job just as well.

 

[swarfrat]

Looks like either way I got to get down to 100% bare wood across the entire face. Was hoping to get there without going bigger than 400grit, but I'm not sure that's possible. (Or would take $40 worth of sandpaper). Even 400 looks rough compared to what I had.

 

[swarfrat]

As for why... It's fretless. Even though it's fine bare, I wanted that super crisp hard finish.  Ugh. I'm done as soon as I get back to presentable

How fine does ebony need to go to get that look? (That it normally has)

 

[stratamania]

400 grit is not going to get you there. If it helps here is an ebony board that I took the frets out of taken to 12,000 micromesh.

ebonyboard by stratamania, on Flickr

 

[lionfeather]

I'm usually happy with 600 grit followed by 0000 steel wool.