What do wood sealers do?
Interesting question. So, lets say that there was a wood sealer available in self=adhesive sheets. This would eliminate the possibility of the sealer penetrating the wood pores and actually providing some level of protection- that since the sheet would have a (adhesive) gap between it and the wood it couldnt be sealed and what about the gaps, small as they might be, between the sheets and at joints? In short, wood sealers provide resistance from penetration by water or other stuff that you dont want to penetrate. Unfortunately, the more difficult a sealer is to apply the better and longer it does its job. In general, sealer has to be applied to ALL surfaces of the wood, not just the side you can see. This means sides, edges, ends the whole caboodle. It may be necessary to double or triple the application on more porous surfaces such as the ends. An oil-based sealer such as is used on decks really should be applied every year even if the manufacturer says that it is good for longer. Sealers that are applied to furniture or other projects that then receive an additional top coat have to be formulated to work with the respective top coat and can be solvent- or water-based.