Anthraquinones and vinegar

I started to write this in a comment in my previous posting, but then decided to write a short post about it as it became so long for a comment. And of course maybe I get new comments and thoughts about this now:)

I had learned from Swedish mushroom dyebooks (several from Erik Sundström) using a vinegar rinse after dyeing with anthraquinone dyes. Sundström has also written an appendix to Miriam Rices book Mushrooms for color about chemistry of mushroom dyes and this is quote from it:
"Anthraquinones. Alizarin, the dye from madder and cochineal, physcion from orange lichens and emodin from buckthorn bark are highly valued natural dyes belonging to the anthraquinone group, characterized by a quinone ring sharing sides with two aromatic rings, which carry many different auxochrome groups. About 20 different anthraquinones are known from mushrooms, mainly Dermocybe, and another 60 from various molds.The anthraquinones occur by themselves or as glucosides, which need a vinegar rinse to make the color fast"

In his books he says that a vinegar rinse is necessary for mushroom anthraquinones, but I have used it when dyeing with madder or cochineal as well and have found it good. To my surprise
I have not found any mention of this in Cardon (though it is such a big book, I might have missed it). I wonder if any historical recipes call for acid after rinse?

In Erik Sundström book Värjäämme yrteillä, sienillä ja jäkälillä (Dyeing with herbs, mushrooms and lichens) he writes that if a dyestuff is a glucoside, the sugers must be unfastened by acid (vinegar). Rinsing with vinegar in the rinse water must be done always after dyeing when using these or similar dyestuffs, so that the remains of the sugars are split off and the color becomes stable and washfast. A suitable acidness is 1-3%, that is at the most 2 tablespoons of vinegar in one litre of water.

I have also a book from another Swedish dyer Gösta Sandberg: The Red Dyes, Cochineal, madder and Murex purple and in that book there is one recipe for cochineal and one for madder which include a vinegar-acidified rinse. In the end of that book there is a chapter by a chemist Jan Sisefsky and he writes about madder that " As a natural dye in general, these (referring to anthraquinone dyestuffs) have coupled to one or more types of sugar that help them to dissolve in the dyebath. Everything indicates that these types of sugars generally split off when the dyestuff fixes itself to the mordant and via that to the fiber." So he doesn't say there is a need for acidic rinse afterwards, and that is in contradiction with what Sundström says.
I believe Sundström is right at least when he speaks of mushroom dyes, but as for the other anthraquinones, I can't say anything. Perhaps this is one of those things of which there is still not enough knowlegde, mysteries of natural dyes:)

To be on the safe side, I have used a glug of vinegar in the rinsewater with all my dyeings, and I haven't noticed any color change or negative side effects, in fact quite the opposite: there seems to remarkably less bleeding in the rinse water after the acidified (is that the right word?) rinse.

Suomeksi
Anteeksi englanninkielinen postaus, tästä piti tulla vastaus edellisen postauksen kommenttiin, mutta kun juttu näytti venyvän, laitoinkin sen sitten tänne, jossa se ehkä myös kirvoittaa lisää mielipiteitä ja kokemuksia.
Erikoista tosiaan on, että en löytänyt etikan käytöstä huuhteluvedessä antrakinonivärien kohdalla tietoja tai ohjeita kuin vain ruotsalaisista kirjoista, toisaalta luotan suuresti Sundströmin asiantuntemukseen, ja olen vuosia käyttänyt etikkapitoista huuhteluvettä kaikissa värjäyksissä enkä ole huomannut mitään haittaa tai esim värin muutosta, itse asiassa päinvastoin: etikkahuuhtelun jälkeiset huhteluvedet ovat huomattavan värittömiä seitikkien, krapin ja kokenillin värjäysen kanssa.