Firstly, I know nada about chemistry...so I'm seeking some info from folks who have the info. I'm a hobby woodworker (actually woodturner), and use polyurethane to finish my work. I usually purchase the poly in quart cans. After using just a small amount of poly and the level has gone down an inch or so, the poly gets a bit thicker and the results are not as good as they were when I first opened the can. I've been told that a product called Bloxygen (inert gas) can be squirted into the can as the level goes down and this will replace the layer of oxygen that sits over the poly. When the poly is in contact with oxygen, this facilitates evaporation, which causes the poly to degrade.
I'm also told by an old timer (excellent craftsman) that by breathing into the can just before closing it, does the same as squirting the inert gas. This would make sense if carbon dioxide is actually heavier than oxygen...
Anyone have any insight to this...
Thanks for any help on this..
Ed