Although the zinc plates that the Lawndale Art Center distributes are supposed to be primed and ready to paint, I find the gray surface just doesn’t give enough luminosity to the image that is painted on top. I prefer to use white acrylic artist’s paint to further prepare the surface of the plate before starting the retablo image.
Place the plate on a coffee can or jar to elevate it and prevent it from sticking to the support surface. Thin some artist’s acrylic paint with water, or a mixture of water and half matte medium and half gloss medium, until the mixture is about as heavy as half-and-half. Then use a large flat brush to paint a thin coat of paint in one direction. After it dries completely, apply paint in the direction perpindicular to the first coat. The idea is to almost float the creamy, loose acrylic fluid onto the plate and avoid brush marks of any kind. If there are any flecks of dried paint, or slight ridges, use a little super fine sandpaper to smooth the surface between coats.
Keep applying paint in alternating vertical and horizontal coats until the plate is a smooth, opaque white, free of any marks. Now you’re ready to transfer your image!