How to Paint on Slate Stone for Outdoors

Gently scrub your slate with water and a mild dish soap, using a scrub brush. This removes any dirt or grime that may prevent your paint from sticking. Scrub the cracks and crevices and rinse the stone well with a garden hose. Allow it to dry for at least 24 hours; 48 hours is preferable. The porous stone must be dry before you begin to paint.

Arrange stencils in a pleasing design and tape them down at the corners with painter's tape. Alternatively, sketch out your design with chalk, making it as detailed as you can. You may paint anything from polka dots and flowers to detailed mountain sunsets.

Paint slowly with acrylic paint using a one-inch, soft-bristled paintbrush. Watercolors won't show up and oil-based paint will sink into the porous rock. Paint big, background details first, applying thick layers of paint. Allow the big details to dry for about 12 hours.

Fill in the smaller details like shading, little buttons, small flowers and eyes with a 1/8 inch or a 1/4 inch soft-bristled paintbrush. Allow the stone to dry for another 12 hours.

Spray the entire stone with spray sealant. Hold the can about six inches from the stone and move the can in vertical, parallel lines. Allow the stone to dry for 24 hours before seating it in the soil.