: Glad this came up again, I've been wanting to ask: Say you've got a half-full
: can of old varnish, stored under suboptimal conditions. You open it up,
: and there's that lovely rubbery skin floating on top. Why can't you just
: skim off what you can, and pour the rest through a funnel and coffee
: filter to remove any remaining nuts & bolts? The solids content would
: be only slightly decreased--basically like thinning. Wouldn't this
: filtrate be useful at least as a first coat, or in less critical areas,
: and preferable to waiting for a household hazardous waste dropoff event?

Well it all depends on how old and thick it is and how cheap and what your expectation
is for the final results.

Yes, you can cut out the oxidized surface and strain the contents. Then you must thin the
varnish with high grade mineral spirits. Make certain it says "for thinning paints" not
"for cleaning brushes".

All these materials are expensive and it pays to start good habits to keep the varnish at it's best.

I have tried every method of dealing with paint can sealing and pouring and keeping the air from drying out the varnish. I’ve never had consistent luck with sealing paint can lids, keeping the lip clean and turning them upside down without leaking. If your varnish is not fresh, clean and scum free everything else is a waste of time.

I now recant my new varnish in quart mason jars with separate lids and screw rings. The mason jar allows me to pour varnish without the lid mess of a paint can. I wipe the jar lip with a paper towel after pouring so the lid won’t stick. By using the separate lids and screw rings of the mason jar I don’t have to worry about not being able to get a lid off if I missed some varnish on the jar lip. I can always pry the lid off and use a new one if needed. I pour varnish into the bottom of a half gallon plastic milk carton. This size carton accommodates my 4” foam brush. Any used varnish gets poured back into the jar unless it is contaminated somehow. Before closing my jar lid I blow propane gas from my small shop torch into the jar to displace air to keep the varnish from skimming over.

All the best,
Rob Macks
Laughing Loon CC&K
www.laughingloon.com