shelf life of spar varnish

[Nebe]

I think spar varnish lasts a long long time as long as you pour what you need to use through a strainer and close the lid tight. If your needles were cracking, I would think that the varnish was not thinned enough and did not penetrate your maple.
Posted from my iPhone/Mobile device

[ed morini]

I would add that any air space left between the remaining varnish and the top of the contain will hasten the thickening of the varnish, even if it is cut. You can blow wine preservative or Bloxen in to the can to remove any oxygen, or you can add clean marbles to the container bring the level to the top and flip the can over. Been doing this for years and will make the varnish last much longer in the can.

Some of the reason the plugs will take on weight after prolonged soaking are the rays found in hardwoods, these carry food transversly through the core of the tree. As the thinned varnish penetrates the lure more sealer is soaked into the stock,adding weight. Trial and error are the only way I know to add weight by this process, but it would vary greatly from plug to plug.

Given that the epoxy coating used on plugs is not completely waterproof, I would suspect the structure of the maple plug would allow more water penetration. The birch on the other hand has a better structure to(somewhat interlocked) to hold off splitting. Just my 2 cents

[Diggin Jiggin]

I haven't turned birch before but I will try some next winter. Until this season I really hadn't had any splitting issues with the soft maple and I really enjoy working with & turning it.

[Rockfish9]

I've found that if you heat maple or birch in a toaster oven prior to dropping them in the sealer they seem to seal better...

.. place some clean brick or stone in the sealer can to take up as much space as possible.to displace the air. then put a piece of plastic film on then hammer the lid down.. I use the same sealing oil for a few seasons... and strain periodically... ...but I use Tung oil

[basswipe]

Spar varnish or any varnish/poly for that matter is not meant for submersion.This is why the finish is failing and the plugs are splitting.