I once mixed up a batch of epoxy with resin and hardener from different types. It produced a crappy result, my guess you did the same thing. Also will second the suggestion that you get the proper ratio (usually 1 to 1). The brands mentioned earlier are all pretty good. Will just add another to the list I like to have is West Systems West System G/Flex liquid epoxy

https://www.jamestowndistributors.co...uid+Epoxy+Kits

I buy the 8 oz kit for $18.99 It does dry amber in color.

Great when you need lots of time (sets in a hour, do give it a whole 24 hours, I like 2 days before I try to sand it), but it's damn strong and remains a bit flexible when cured. I particularly like it for firewalls, dihedral braces, setting horizontal and vertical tails, and hinges. Because it gives me plenty of time to get things just right. I've even use it to fuel proof.