I recently acquired a volume from the famous Bibliothèque de la Pléiade from an antiquarian bookseller. These volumes always have two fabric bookmarks and as you can see from the image below, the bookmarks in this volume are creased.
I would like to iron the bookmarks but I have no idea what type of fabric Gallimard uses for them. Hence, I don't know at which temperature I can safely iron them. Can anybody give advice?
Update: Since the age of the book may be relevant to the materials used for the bookmark (i.e. synthetic or not), I want to add that the volume in question is Albert Camus: Théâtre - récits - nouvelles, edited by Roger Quilliot. Bibliothèque de la Pléiade. Gallimard, 1967. (This volume is not to be confused with Théâtre - Récits et nouvelles - Essais in two volumes, published in 1980.)