This stuff is amazing! well I think so!! I've used on my carpets and upholstery no end of time.
We've had black bits of dirt in the carpet from shoes, I've also tried it on sticky bits like where pritt stick glue has got on chairs and then goes a bit black with stuff sticking too it.
All it takes is a jay cloth, you scoop a bit onto the jay cloth and rub over the stain, let it soak in a little if it's a deep stain. then rub or scrub like mad to draw the stain out.
it's enviromentally friendly, it's not full of chemicals it doesn't smell of anything, however sometimes depending on where you store it, it can develop black moldy bits but I just take them off.
The only thing I would say is test it on a hidden piece of carpet or material, I have not found any that it doesn't like but always best to check.
I get addicted once I've started with it, I do the bit I got it out for then look around for other bits I can have a go on it's so satisfying!!
The cost is around about £5 a tub, however I got mine on ebay three tubs for £12. They aren't there at the moment, I've also just found it on Proidee.co.uk 3 tubs for £14.50 and it's also found in Lakeland.