What do you put on glass after painting it to keep the paint from chipping?

To protect painted glass and prevent chipping, you can apply a clear acrylic sealer or a clear spray varnish. Make sure the paint is fully dry before applying the sealer, and choose a product that is compatible with both the paint and glass surfaces. Lightly spray or brush on a thin, even coat, and allow it to cure as per the manufacturer's instructions for optimal protection.