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Although it is not necessary to give a painting a final varnish there are certain benefits that should be seriously considered . Some colors have a tendency to sink in and become dull and environmental agents such as dust, moisture, smoke, etc. can harm a painting over time. Paint dries very slowly and although a painting might feel dry to the touch the drying process goes on for about a year. During this time the paint molecules interact with oxygen and other particles in the air having a tendency to make the surface yellow slightly. A varnish acts like a protective layer that when properly applied, slows down the yellowing effect and brings out the luster and glow of the colors of a painting.
Avoid varnishing a painting when the temperature is either too hot, too cold or on rainy days (moisture creates blooming effect). Make sure that the room you are working in is dust and draft free.
Start by brushing loose dirt of the painting surface with a clean dry brush. Do not use mineral spirits! If a stubborn stain exists dab the painting surface gently with a surgical cotton pad dampened in distilled water.
For Gambar add 1 1/2 tsp of their beeswax medium to the varnish. Then heat the beeswax in a double boiler and add the varnish mix while constantly stirring. Apply using a foam brush or a 2 in mongoose brush to avoid bubbles or loose hairs on the brush on the surface.
Note: It's best to mix enough varnish for several paintings
If an area was missed when varnish was applied - wait 10 min and reapply - varnish will set within 10 days and touch ups can be done during that time before it sets.