Rules of thumb for magical experiments in general:
If you didn't know it could result in Dhar but it does, that's a hazard of the job. If you knew it would result in Dhar but do it anyway, that's a burning. If you suspected it might and do it and it does result in Dhar, then the Dhar poisoning that would normally result is considered convincing enough. If you continue that same line of experiments and continue creating Dhar, that's a stern look and a very serious warning and all benefit of the doubt is lost for future experiments. If conventional wisdom is that it would but you didn't do the research to know that and get Dhar, that's pacification because you're clearly a threat to yourself and others. If conventional wisdom is that it would but you manage to find a way that it doesn't, that's fine. Wonderful, even.