About "coated":
A complex composition: aluminum foil is laminated on canvas and serves as a reflector for light (daylight as well as artificial light).
Case 1 = large-area lamination of aluminum foil: a transparent acrylic paint is applied over this, in different layer thicknesses, so that you have different color effects partially - depending on the reflection of light - almost only aluminum foil is visible up to fully opaque acrylic paint, where the light cannot get through the thick, intensive layer of my paint.
Case 2 = small-area lamination of aluminum foil: further acrylic paint is applied (in different color variants) next to the aluminum foil(s).
A transparent, usually colored bubble wrap is then stretched over it (in both case variants), which, like a transparent color varnish on the “underpainting” (= aluminum foil + acrylic color glaze/acrylic paint), gives this underpainting a new color value (optical addition of the color values).
Another optical effect is that when the picture is viewed at an angle, the color of the bubble wrap becomes more visible, but when viewed directly from the front, the optical color addition comes into its own.
About bubble wrap: The quality of bubble wrap varies widely - thicker foils usually have a surface that can be stretched smoothly, thinner foils can often not be stretched out so smoothly, therefore giving the picture a more restless, sometimes wrinkled surface and is therefore a desired partial aspect.