I'm no expert but I think without hardener it won't harden at all. When I was making my seat bases the coats I noticed a huge difference depending on how much catalyst I used. Sometimes it would harden to the touch in an hour or less, sometimes a day or more. I was mixing up different size batches and guestimating how many drops of catalyst to use.
Maybe try coating a 2"x4" with different resin/catalyst ratios (or no catalyst at all) as an experiment?
-Justin