I remember this one, and thinking the Plaintiff did just that, and yes, that will ruin hair. Late 80's/early 90's, I had a huge mane of mall hair. It was glorious. I also used to do higlights. I did Sun-In once, and took a curling iron to it, and it got wicked with the effect, but my stylist read me the riot act. BUT.....he told me about this new technique that he went to New York to get certified in and it was totally safe. It would take about 4 hours to per my hair. It was long and thick. Then, while it was still wet after washing the solution out, he'd color it, using something called Sun Glitz. It was all kinds of weird colors (green, blue, etc) and I looked like a beach ball after he pulled all of my hair through a cap, but the results were nice. I would be at the salon pretty much all day, and back then, it would easily be $150 or more.
After a couple of treatments, my hair started to fish hook. He told me it was normal and he'd trim it off. It got to the point where I couldn't comb it anymore. The underside was so knotted and matted that it would be knotting back up as soon as I would brush it. It was horrible. He would tell me it was OK - that sometimes happens, and it would just give me good volume (yeah, I know, but I trusted this guy who was trained in name brand salons and certified, etc). Then he would spend an hour brushing it out, only for it to knot back up.
Eventually, he left to go to another area - a larger city. My mom followed him there - she'd drive over an hour each way for him to do her hair. I opted not to - it was too much hassle. I went to get a top perm before my wedding, as the top wasn't holding on like it used to. The place I went said my hair was badly damaged, and they tested my hair in perm solution - it essentially melted. They recommended I let it grow out as much as I could and get it checked again before I got married. I found someone to give it a minor perm, and then decided to let it grow out. I went to another salon, and the underside was so bad that they said my best course of action was to cut it all off. All....of....it....and start over. I've had short hair ever since. Chatting with the stylist who cut it off, she was shocked that he would perm, then directly color it, and that Sun Glitz was extremely harsh just on it's own.
I'm not one of those people who says that one perm eons ago ruined their hair, but overprocessing definitely ruined mine. It's been extremely fine since then, and the top has continued to thin out. Depressing. I'm extremely fussy about any processing I get anymore.