Lay the new canvas down on a hot table and coat it uniformly with relining wax, which is often beeswax or synthetic wax mixed with resin. Find these items at stores that sell merchandise for fine art renewal.
Carefully set the antique painting down on top of the waxed canvas, face up. Ensure that the edges are square and that the entire back of the painting will be reinforced.
Heat the hot table to the melting point of the wax, so that the two canvases adhere together and the wax permeates the canvas.
Avoid putting pressure on the painting; let the heat bond the two canvases. Watch the painting closely during the process for changes in paint color or texture.