how is this possible?

Well, I'll throw in my comments but remember, I am not an expert (just look at My hair )

I don't know the science of it but I think that after a while, the cuticle of the hair is damaged (open) so the semi reacts like a permanent and does not just coat the hair but actually 'goes into' the hair shaft....

I would suggest that you use a filler before using hair color.  Sounds like that might help the color stay longer. 

Good luck.  I'm glad you like your color.

Braelyn

ok, first off, im not complaining. im actually thrilled with my results. but im confused.

in the past ive always kept my naturally lt reddish brown hair a medium reddish brown. until about 4 months ago, i decided to kick it up and go red. I tried permanents, they just faded. i tried semipermanents, which looked great until i washed it even once. It was hard for me to even get the vibrance i was looking for..my stylist told me it was due to the excessive buildup of haircolor, so they stripped it, and redyed it. Once again, looked great, til i washed it. Now i know that red is difficult to keep, but i had all the shampoos, and conditioners, and products intended to preserve it, and it just wouldnt hold the red.

I picked up one of the drugstore type temporary colors, intended to last like 8 shampoos. And 4 weeks later its still bright red. Im really happy with it, but i just was hoping someone could explain why a temporary would last better than anything else . ive never had anything like this happen before.

Any ideas?