As with most CA products, the shelf life of GluBoost should benefit by being kept refrigerated but only under certain conditions. As you already pointed out, humidity and moisture is problematic for CA. In my opinion, refrigerating open bottles can be more problematic especially in humid climates. Humid air fills the empty space in the bottle, then refrigeration tends to cause the humidity to condense which could directly add water to the CA - this would not be good. Also pulling the refrigerated bottle out would cause humidity to condense on the outside of the bottle as well.
I only refrigerate my unopened CA, including GluBoost. And then I pack it inside a plastic zip-top bag along with a silica-gel based desiccant pack in the bag. Then all of the bags go into a gasket sealed plastic ammo can before going into the refrigerator. So far so good, none of the indicators in my desiccant bags have changed color yet and so far the CA I have pulled out and started to use has all done just fine.
It would surprise me if Pens Plus would be impacted by hot and humid conditions, however, blushing is caused by moisture that gets trapped in the finish and since it contains alcohol which is hygroscopic, it would naturally absorb some of the moisture from humid air. The general maximum humidity level stated by most pre-mixed shellacs is in the 80% range, so high humidity means really-really high.
In other words, in a very humid environment, I would opt for a friction polish like Pens Plus over a CA finish. If you don't want to buy it, you could always whip up a batch of O.B.'s Shine Juice if you have the ingredients on hand. It's equal parts of De-Waxed Shellac, Boiled Linseed Oil, and Denatured Alcohol - very similar to Pens Plus which is essentially Shellac, Walnut Oil, Alcohol and a Microcrystalline Wax.
Regards,
Dave
