Seal your canvas with acrylic gesso.
If you are planning on doing an acrylic painting, or are planning another project, you can seal the canvas first with acrylic gesso. Acrylic gesso protects your canvas, tightens it up a bit and provides a white surface for your painting. Once the canvas is sealed it is protected from elements in the paint, and the white surface reflects light, which will help keep the translucent areas of your painting luminous. Acrylic varnish is applied once the painting is completed. The varnish seals the acrylic paint skin and protects the painting from the elements
Instructions
Seal the Canvas
1. Lay the canvas down on a flat surface or mount it on the wall.
2. Fill the can about halfway with water and dip the paintbrush in the water, dip it in the gesso and apply it to the canvas in a back and forth, horizontal direction. Do not dilute the gesso by pouring water in it. A little water on the brush is enough to make it workable.
3. Continue applying the gesso in the same manner, and work from top to bottom, working the gesso into the grain of the canvas until you reach the bottom.
4. Allow the gesso to dry, about 30 minutes, and sand the canvas gently with the sandpaper.
5. Apply the second coat of gesso in the opposite direction of the first, vertically.
6. Allow the second coat to dry and sand as you did after the first coat.
7. Apply a third coat of gesso in the same direction as the first coat. Sand it when it is dry. The canvas is now sealed and ready.
Seal the Acrylic Painting
8. Wait until the painting is completely dry before applying varnish.
9. Place the painting flat on a horizontal surface.
10. Pour a little of the acrylic varnish into a bowl or jar with a wide opening.
11. Dip the brush into the varnish and apply it in a back and forth motion on the painting. Brush lightly, not vigorously, or you will create bubbles.
12. Work from the top of the painting to the bottom until the painting is covered. If you miss a spot, don't try to go back and cover it while the area is wet. Wait until the varnish dries and then retouch the spot.
