Handling and storing varnish is much less complicated than working with it. As long as you follow a few basic tips, your varnish will keep for extended periods and will be ready for use when you need it.
Store at Moderate Temperatures
Varnish should be kept between 50 and 80 degrees F. If varnish gets too cold, it becomes difficult to brush or roll. If it gets too warm in a sealed can, the seal could disappear, and the container of varnish would go to waste.
Store Upside Down
To protect the seal, store the can upside down. This practice will prevent air from getting into the container and hardening the varnish. If you need to store leftover paint, use this same trick. It may increase their shelf life up to several years.
Avoid Direct Sunlight
Do not store varnish in direct sunlight. Ultraviolet light can cause chemical reactions in the varnish, and the reactions will affect its ability to cure properly. If you must transfer the varnish to another container, pour it through a paper strainer to prevent contaminants from being passed from one container to the next.