I have an arborite kitchen countertop over which I would like to apply more arborite. Do I have to remove the existing arborite or can I just put the new over the old?

Both methods can be used to improve your kitchen countertop. If you simply put new arborite over the old, the new arborite will not stick well to the old because of its glossy surface. Take a circular sander and rough up the surface. This will allow the contact cement to bond with the surface. If you choose to remove the existing arborite first, use a hot air gun or an iron to soften the glue and you can work a spatula under the arborite to lift it off the counter.