"I don't know yet," Roxanne said. The incantation had been sound, as had the wand movements. Everything had seemed normal until the handkerchief changed. Odd.
"Remain still, please." She came closer, right up to Glendga, and slowly cast a diagnostic spell, tracing her own wand down Glendga's wand arm but about an inch and a half above. The spell took several minutes to work, but it was far stronger than the instant-answer ones every good housewitch knew. Roxanne left it glowing in the air above her patient's arm and examined the handkerchief. It seemed to have just changed the material - well, and the smell, but there was little she could do about it. In any case, the smell was probably not a clue, at least no greater a clue than the fabric itself.
Murmuring the incantation to turn the handkerchief back to what it had been, more or less, she examined it again before casting her own warming charm. It worked without incident. She cast a quick finite incantato and spent another moment pondering over the square of cloth until the glowing line above Glendga's arm changed colour, upon which she turned her attention to it instead.
The line was no longer as straight as it had been - it buckled and curved, and in one place threw a shining loop into the air. "Hmm," Roxanne said. "It's difficult to say for certain without a record of your usual results, but it doesn't indicate any abnormal quantities. Of anything - chemicals, magical damage... you seem quite healthy." But that, of course, couldn't be true. Simple charms didn't go so wrong as that for no reason.
"I would like to repeat the demonstration," she said. "But with one change." It was best to be sure. "It may be uncomfortable, but I would like for you to use my wand this time, and vice versa." And she held her wand, about the same size but of a slightly warmer paleness, out to Glendga. This was often unpleasant for wizards, but Roxanne had long lost any squeamishness over wand ownership.