Meths will leave a stain but it's very, very feint. If anything it appears slightly grey rather than purple. You need very good light even to notice it and even then you may not notice at all. The rosewood sanding dust is probably the culprit. The best way to get rid of it is to scrape rather than sand. Sanding tends to push the stained wood deeper, so you have to remove more material before you get to the clear stuff. Indian rosewood can be nasty at releasing it's dye, wiping it with shellac releases the dye, ready to deposit it on any light coloured inlays.
If you want to avoid the purple meths then buy the high % Isopropanol (isopropyl) alcohol. It flashes off slightly slower than the new meths formula but it's perfectly fine for French polishing or spirit varnishing. Meths no longer contains any methanol, it was a small percentage even when it did. It is mostly ethanol.
100% alcohol isn't possible, it is hygroscopic.
If you want to avoid the purple meths then buy the high % Isopropanol (isopropyl) alcohol. It flashes off slightly slower than the new meths formula but it's perfectly fine for French polishing or spirit varnishing. Meths no longer contains any methanol, it was a small percentage even when it did. It is mostly ethanol.
100% alcohol isn't possible, it is hygroscopic.
