I sanded one of the test blocks I made. The block was chosen because it had a nice rich color. It had only been soaked for a couple of days. I have some that were soaked much longer, but I've forgotten which colors were soaked for what length of time. The block I did sand (purple) did not have very much penetration at all (to my surprise). The color sanded of with only a light sanding with 80 grit paper.

What I need to do is put a bunch of 2x2x4 blocks in and take one out each day and number it and keep a log of how long each was soaked, then slice it on a saw and measure color penetration.

I used two packages of RIT dye in about 2-1/2 gal. of water. I think if it was soaked for about three week the dye would waterlog the wood deeply enough to allow sanding (dependant upon wood type). It might help to start with extra dry wood. I think it would be good to move it into a new batch of dye each week too. The dye costs about $2.75 per pkg.

If someone wants to try these combinations and post results, it'd be worthwhile. Try it with and without changing the blocks into fresh dye, and go for as much as a month of soaking (let them waterlog). Blue and Purple are good rich colors to use. Green turned to black with extended soaking, but not so with most other colors. Surprisingly, yellow got rich in color quickly (it was a golden yellow).

I didn't try UV resistance testing.