Thank you "The Fount of all Knowledge" (You Ken? Och aye!

) for your comprehensive, as ever, answer.
Coudn't Wouldn't have put it better myself.
Mark, I make it up with warm water, apply with a pipette, cover with a dry cloth and then hold a hot iron over it. As in many cases the carpet is wool rich I find about 30 seconds or so is sufficient to see if there is an improvement in the stain. If improving then apply further heat.
When ready to assess, flush out to neutralise the reaction. To really check on results dry off the carpet with a hair dryer (get the best you can by going to a ladies hairdressing salon and buy the type they use).
Then if necessary start the process again.
Does that answer your question, Mark?
Roger