Hi Tomas,
So while you can get away with varying the hardener a little bit one way or the other, varying it by as much as a third is likely to cause problems. If you use more hardener, the pot life of your resin will be shorter. Your resin may cure ‘extra hard’ and become brittle later. By using less hardener, your mixed resin won’t generate enough heat, so it won’t cure completely or stay mostly sticky at the end of the cure time.
To know whether or not your resin is mixed well, I like to use a rule of thumb to mix the two parts together for 10% of the pot time. For example, the super clear resin pot time is 25 minutes, so I like to mix for 2 1/2 minutes before pouring. Make sure to scrape the sides of your cup and mixing utensil multiple times during the process.