More on Madder

I have had an email asking me what the pH of the madder bath,which gave the red,was. I did not know but belatedly realised that the spent bath was sitting outside my studio waiting to be used for brown, so I tested that and found the pH was about 6. I assume that the pH would not have changed much and I was quite surprised that the bath was so acid. Then it occurred to me that the bath had definitely fermented when I first dyed with it. It had bubbles on the surface and the sweetish smell of a fermented bath. I know from studying fermenting indigo vats that fermentation produces lactic acid so that the pH goes lower so I wonder whether the fermentation lowered the pH
Is the production of a red due to :
1.low pH,
2.Fermentation which releases the red dye and causes a lowered pH
3..Long soak giving the red with its lower solubility a chance to appear.
4..All three
It makes one realise how very very complex a dye madder is. I think I will try adding vinegar to reduce the pH for the next experiment without the long soak.