Excellent, I've been trying to figure out how to decorate like that, for a lime-wood ladle that I have all but finished. I tried cutting a thin strip of wood out for each line, as Jogge Sundqvist shows in his Swedish carving DVD, but I just couldn't get the clean cuts work using the cheap (<£5) set of Toolzone woodcarving tools I picked up a few years ago.
So, if I understand correctly, with Kolrosing you are not actually removing any wood but instead, I suppose you either compress or perhaps score it? Then rub something dark, like coffee grounds, into it afterwards. [Any chance that you could post a picture of the tool you used - or an image link of a similar looking tool?]
I love the pattern, especially the cross-hatching and the elaborate sun pattern above - v. effective. Do you pre-draw the pattern with a pencil or just free-hand it (or use a ruler)?