Lady Sings the Blues
1) If bluing can stain fabrics, then it functions much the same as a dye. There are many, many different kinds of dyes, some natural, most synthetic. Many natural dyes can be washed away - just like some kinds of bluing. Same difference.
2) Examining a "colour" wheel is certainly no bother. I remember seeing one for the first time about the 3rd grade. There is no question that bluing tends to cancel out slight yellowing. The problem is that it can also be used to cover up residual grime from insufficient cleaning. Among some of my friends, those little old white haired ladies are known as "blue-hairs", because an excess of bluing in their hair treatments has DYED their hair light blue.
3) Personally I prefer a warmer, natural looking white to a bluish-white for cottons and linens. Walls, ceilings, cars, and appliances, as well.
4) Yes, chlorine bleach is a major cause of yellowing of cottons - if not the only reason for many homes. I don't use OBA's or bluing for my whites, and they have not yellowed. The trick is that I also don't use chlorine bleach. Instead I use a non-OBA HE detergent and STPP, plus hot water and the longest possible cycle. Whites come out very clean with no need for bluing.
5) I don't mean to knock bluing - it's a great old-time laundry component, and in fact I'd prefer it to OBA's, which I agree are rather nasty compounds. I happen to have a little jar of OBA dye powder. The chemist who gave it to me warned me to be careful with it because of the toxicity. I've never used it. Interestingly, the powder has a light green tint to it. But what with the elimination of phosphates from modern laundry detergents, the stampede back to cold water washing, insufficient rinsing in dumbed down top loaders, and uninformed people who over-load their washers, habitually dose their whites with chlorine, it's probably necessary to have OBA's to help cover up the residual grime and chlorine-caused yellowing. Too bad!
