A Few Home Truths
1 - Bluing is a tint, not a dye. Properly diluted and used bluing cannot "dye" anything. Undiluted liquid bluing will stain however, but ultramarine blue is easily removed.
2- If laundry is done properly there shouldn't be any dirt/soils/stains left by the final rinse,which is when bluing is used. Bluing is used to counteract the tendency of white cotton and linen fabrics to have a yellowish cast. If anyone has ever bothered to examine a colour wheel, they would know colours opposite each other on said wheel cancel each other out. Blue is opposite yellow. Besides white textiles a slight blue tint is used on white paper, white fur/hair on certian animals, and even white/gray human hair.
3 - Besides cancelling yellow, to North American and European eyes, bluish white appears whiter; while in South America reddish tinted white is "whiter". It is no accident that many laundry products have or had blue colouring and the colour blue is associated with laundries/laundry. Ice blue or snow-white blue whites have been the standard for properly laundered whites for ages.
4 - Bleaching cannot and will not render items bright blue/white on their own, especially chlorine bleach which after repeated use can give textiles a yellowish tinge.
5 - Bluing was replaced by OBAs mainly because the former works only with cotton, wool, and linen textiles. For nylon and other man made textiles OBAs are better. However OBAs are made of some very toxic substances, and furthermore bind to skin permanently. If one doubts this, simply examine one's hands or arms in a dark ruum under black lighting. You will see just as one's textiles laundered in detergents with OBAs glow in the dark, so does any thing else said textiles have come into contact with. This is the reason many people choose OBA free detergents.
L.