Proper Varnish Storage
Does varnish go bad sitting
on the shelf?
Unopened varnish should last for years on
the shelf when kept away from excessive heat.
When a can is opened and the finish exposed to oxygen,
curing can begin. If the finish skins over, remove
the skin and add mineral spirits to restore the original
consistency. Water-based finishes have less tendency
to skin over. If they do, add a bit of water to
restore the original consistency. It’s always best to test
old varnish on a piece of scrap to make sure it’s drying
properly before you apply it to a project.
To maximize your varnish’s shelf life after it has
been opened, transfer any remaining finish to a smaller
container. This will minimize the amount of oxygen
in the container and preserve the varnish (see photo,
right). Be sure to date and label the container. If
you’re using a glass jar to store the old varnish, be sure
to keep it out of direct sunlight to prevent damage
from UV radiation.
You can also try Bloxygen, a product that is sprayed
into a partially used can and forms a gaseous barrier to protect the varnish. It also protects other solvent-based
products, such as wood filler and paint, although it will not
protect lacquer or water-based finishes. One can is good for
approximately 75 applications.