Pro Tip: If you want your epoxy resin it to cure harder. While mixing, let it induct heat in the container until it hits 93 degrees. For an accurate temperature, just use an infrared heat gun or you'll feel the cup start to get warm in your hands. Keep the room temperature up for at least 24 hours around 75 degrees or more. You will be surprised at how much difference it makes by letting the epoxy get a little warmer in the mixing container itself.
DO NOT add more hardener to the mix, this will make the final cure tacky or sticky.