What is the mechanism underlying those all-too-common garden variety stains such as those due to blood, ink, rust, coffee, etc. (i.e. as opposed to industrial and/or deliberate staining) .
Are stains which are difficult or impossible remove merely due to covalent bonding between the staining material and the stained material? Do more readily eliminated stains such as those due to, say, tomato sauce, arise from hydrogen bonding, weak covalent bonds, or something else entirely?
On the other hand, I suppose it’s possible that the chemical processes behind stains are more complex than simply talking about hydrogen bonds and the like.
I’ll answer this on the fly for now and look into it more in depth later.
I think in most cases, it is unlikely that a stain is the result of covalent bonding. I think it is more a result of how deap the pigment molecules get into the fibers of the clothes and how well the pigment adsorbes onto these fibers.
Well I know that bleach oxidzes stains to make them appear less colored, and does not actually remove the stain. So whatever it is, it’s in there good. I can’t see how covalent bonding is going on, your clothing is already in a pretty stable form (cellulose if it is cotton) that requires enzymes to actually catalyze reactions with it. I’d bet there are hydrogen bonds going on though.
I’m going to agree with **Christopher **that it’s the pigment getting stuck deep within the fabric, and after drying the solid chemicals in that liquid will be very tough to remove. Thus oxidizing them with bleach is the only way to go.