The pH of the wool cleaner I am using is indicated as 5.5 to 6.5 on the label. I also did a dilute vinegar pre-rinse (with a wet Challenger pad) in case there was something alkaline on the carpet to start with.
I thought maybe I am getting the rugs too wet or that some wool rugs cannot tolerate water?? Or maybe the vinegar did it?
It's as though my treatment highlights different yarn spools in the rug. Yarn spool 1 covers 6 inches, yarn spool 2 covering the next 6 inches reacts differently to water, etc.
Could it have been a silk rug? Materials made of silk can react badly when wet. When I am cleaning what I believe to be a silk rug, I don't pre-spray the rug itself. I spray the pad instead, up to the point where I can hand-squeeze the excess cleaning solution out of it. Then I clean with the medium glider.
Could be. The standard liability policy for carpet cleaners, unlike a physician's malpractice policy, does not cover the floor covering you are working on. It covers other damage you might cause from your working on the premises.