mend a tear in a canvas?

Question

Acrylic paint on the front

Answer 1

canvas on the back, use rabbit skin glue or some other size (perhaps PVA glue) to glue together tightly

Answer 2

I've used matte varnish or matte medium lathered onto a square of canvas not much larger than the tear. Place a block of wood or other flat surface on the front and press down from the back once the canvas patch is applied. Watch for any bleed through of the matte medium and wipe what does come through. Be sure to smooth out the tear from the front by reversing the block. After it dries you may have to touch up the front with matching paint and maybe mixing in a llittle modeling paste with the paint, depending on the texture of the original. I've done this to about six paintings and it seems to work fine, although they were not musuem quality repairs.