How to Varnish Painted Glass. After you've completed your painted design on glass, you need to keep the image from peeling and chipping off by applying a protective varnish clear coat. Here are a few tips when you varnish painted glass to ensure the entire design stays protected from regular use.
Things You'll Need
Flat broad brush
Pour a small amount of clear coat onto a painter's tray so it's easier to access with the paintbrush.
Dip a flat broad brush into the clear coat and begin applying it to the painting. Starting at the top outside edges of your painted design, brush the varnish on top of it, taking care not to go outside the painted lines.
Brush on the varnish in one direction. Beginning at the top of your design, cover the area from left to right and then move down to the next area. Doing this allows you to keep track of where you have applied the varnish and where you have not.
Hold the glass at an angle once you finish applying the varnish to check for spots you missed. The spots that you missed with the varnish look dull in the light. If you find a dull spot, simply apply varnish to it.
Always use a waterproof varnish. These types of varnishes are much more durable and offer better protection for painted glass than varnishes that are not waterproof.
Never put painted glass in the dishwasher. The harsh cleaning action of dishwashers peels off the painted design.