Glue/Backing Bleed-Mahogany Veneer on Snare Drum

This is my first post here. I was directed to this forum by Joe Gorleski at veneersupplies.com who said that mahogany may have a fleece backing. I am working on an older Slingerland Snare Drum, most likely built in the 1950s. I was carefully sanding the outer mahogany ply of the 3 ply drum (Mahogany, then 2 plies of maple). Afterward I wiped it down with mineral spirits and noticed some white lines in the direction of the grain. It dawned on me that I may have sanded down too far although I was quite careful no to. I plan to use Waterlox Original Satin as the finish. Is there anyway I can darken the white lines? Any other suggestions? I have attached two pictures to show what I am dealing with.

Perhaps that's something coming through from the back, but I've seen white streaks like that in solid mahogany.

Usually sand-through looks different. A whole area starts looking a different color from the surrounding area. It almost looks like a bruise. Not little streaks like that.

I agree with Jamie. It doesn't look like sand-through to me either unless the veneer already had holes that were uncovered by sanding. Are you sure it didn't look like that before you started sanding ? Could it be sanding dust caught in crevices ?

I believe, if the mineral spirits didn't change the color of the white spots, no coloring agent would that didn't also change the color of the mahogany. You might examine the holes to see if there is any kind of material between the veneer and the substrate.

Thank you for the responses. I know that the mahogany did not look like that before I began sanding because I wiped the entire shell down several times looking for items to sand specifically. I thought it might be sanding dust at first, but with the dust being the mahogany color I dismissed it. I got the idea this evening to take a sewing needle point and run it back and forth lengthwise on one of the lines inside the grain of the mahogany. With a little bit of effort, I was able to scrape out of the wood grain whatever the white material is. I cant imagine doing this to every single grain groove on the veneer. Any thoughts as to how I could remove whatever this material is. By the way, my progression in sand paper was 150->220->320.

Is it possible that the drum originally had a shellac finish? If so, that could be shellac swarf which the mineral spirits wouldn't dissolve. You might try wiping it with some alcohol to see if the white dissolves.

Mahogany can sometimes have mineral streaks that look just like your photos. Try finishing a small area to see if it just blends in with the rest of the surfaces.

In the same vein as David's post, try a little lacquer thinner if the alcohol doesn't help just in case the original finish was lacquer.

Thank you all for your advice. I an convinced that the white streaks are indeed mineral deposits. The white streaks are very hard. I was able to sand a little deeper and remove approx. 75% of the deposits. I left the remaining deposits to keep a little authenticity with the drum. I find it interesting to know that Slingerland used genuine mahogany back in the 1950s. I tried alcohol with a toothbrush and it didn't make a difference. I put 3 coats of Waterlox on the shell and it looks great. The mineral deposits remained even with Waterlox applied.