Athlete from an athletic family...
2 towel sets:
- "Whatever" (cheap/replaced fairly regularly) whites that go to sports stuff ((that I'll call gym towels from now on just for space, even though the gym may be the cleanest place those towels go.))
- Good cream towels (that be come white with washing... The trick to snowy white towels is to buy creamy ones, that bleach to snowy white... Instead of crisp white that bleach and stain kind of bluish grey or dingy yellow)
Both sets are washed & dried on hot with detergent & bleach
Gym towels are periodically left to soak overnight in detergent & bleach
Gym towels are replaced as they wear out, & are cut up for rags
The bleach is the key with athletes. Our body oils trap dirt/skin in the fabrics. True for normal people, too, but athletes are constantly wiping their sweat (and oils) on towels, and bathe more (getting even more oils into the fabric). Degreasers like dawn can help with colors... But nothing works as well as bleach at denaturing oils & skin cells.
The sour smell & funky texture in towels are decomposing body oils and skin cells trapped in the fabric.
Similarly...
- Good towels = wash weekly (at least)
- Gym towels = wash after every use, bleach overnight monthly