Let's see if we can clear things up. Our Rust-Oleum Varathane Wood Putty does not harden or dry. If you are looking for a hardening filler we recommend using our Rust-Oleum Varathane Wood Fill Stick.
https://www.homedepot.com/p/Varathane-3-2-oz-Natural-Wood-Fill-Stick-340478/305560004
-Rust-Oleum Product Support 14