You can also use acrylic medium as a dry adhesive. First coat collage elements and the support surface with medium. Then allow the medium to dry. Next, iron the elements onto the surface. The heat of the iron melts the dry medium and fuses the layers. Note that the support surface needs a rigid backing during the ironing. If the canvas is prestretched, a book will do. Also, the elements must be protected with silicone release paper during the ironing process.