Bursting bottle

Yes, that blonding of the hair went very well thanks for asking. I was a little worried that I would end up looking too blonde, or just fake, but it looks exactly like it does when I've been to the hairdresser. Because I have relatively little hair, very thin, I didn't need the whole bottle. Well there were two bottles, one with something liquid and a creme to pour into it and mix before using. I only used half of it, and was planning on saving the rest for another time. Next day when I got home I noticed the bottle had tipped over. It had kind of expanded and become rounded. V. weird. Until I read the instructions, saying expel of any leftover liquid immediately. Oh dear. So I shucked it in the bin and then promptly forgot to take it to the trash container outside. It is still there, and I'm kinda waiting for it to pop. Yeah, I live my life in the fast lane! I realize it created some sort of chemical reaction, but have no idea why. Aussie girl?