4. Ink, marker and dye transfer: solvent first, patience second
Ink is a dye suspended in a carrier, and the carrier tells you what to use. This is the family where a quick, aggressive approach works better than a long soak.
Place the stained area face down on a thick pad of white kitchen paper. Everything you dissolve needs somewhere to go, and without the pad you simply move ink around the garment.
For ballpoint, dab the back of the fabric with isopropyl alcohol on a cotton ball, or hand sanitiser, or an alcohol-based hairspray if that is what is in the house. Do not rub. Dab, then move the garment to a clean part of the pad, then dab again. Watch the ink transfer to the paper. Repeat until nothing more comes off, then wash with detergent.
Permanent marker responds to the same treatment but may only fade. Gel and fountain pen ink often do better with cold water and biological detergent than with alcohol. Dye transfer — the pink shirt caused by a stray red sock — needs a colour-run remover product, and it works far better before the item has been dried.
Check the garment before it goes anywhere near a tumble dryer or a hot iron. Ink that looks gone when wet often reappears as a faint grey shadow as the fabric dries, and heat at that point bonds whatever is left for good. Let the area air-dry fully, look at it in daylight, and repeat the alcohol and wash cycle if anything shows. A shirt can go through this three or four times without harm. It cannot come back from one pass through a hot dryer with ink still in the weave.
Two cautions. Alcohol can strip dye from acetate, rayon and some dark cottons, so test on a seam. And on leather or suede, stop and go to a specialist; home solvents remove the finish along with the ink.