Discovered something quite by accident a few days ago. Was ironing a chiffon skirt on a ballroom gown, and suddenly noticed spots of sticky goo forming on the skirt, iron, and ironing board. The skirt is stoned. I'm assuming that the stones were hot-fix and the ironing re-melted the glue . What a mess. I've ironed other stoned skirts with no problem so I was not expecting this at ALL. Even trying to carefully iron around the stones still created too much heat. Crap.
Press cloth is a great idea ... perhaps lowering the heat setting of your iron for that particular garment .... Were they Swarovski hot fix crystals? I'm worried that the glue adhesione will not be as strong as it was before.... best of luck!