Smiling, Bryony nodded. "Of course," she said. "You don't need to charm the book first, but it helps." She opened her sketchbook again, more to have something to do with her hands while she explained than for any actual demonstrative purposes. "If you're charming an individual page you have to find the other side of the leaf that would have been attached to the one you remove and individually seal it to the spine," she explained. "That's why most magical sketchbooks come pre-charmed to do it automatically."
She stopped leafing through her sketchbook and reached into her bag to see what else she had with her. Her journal (that she'd brought in case she and Theo couldn't find one another) and a fiction book. She was reluctant to remove pages from either - especially the journal, which was already imbued with such complicated magic. "It's not a severing spell," she said. "It's - a separating spell, I suppose. You're separating the page from the binding that holds it to the spine." She flicked to the back of her sketchbook and showed Theo the last page, and the way it was actually the same sheet of paper as the first page. "If I just ripped this page out, I'd risk the first page coming out in time too, see?" She didn't know if she was explaining this well at all. She performed the spell once more, slowly so that Theo could see the movement and hear the incantation. "That's the separating spell. And my book will automatically seal the first page in." She gave it a tug to show that it wasn't loose.