Epoxy is a polymer, means when you mix it its creating chains of units, and if the amounts are not mixed well there will be unsatisfied pockets of one ingredient.

That also means that its starting to create those units into chains as soon as one ingredient comes in contact with the other.

Before I mix I put the two bottles into hot water from the faucet, it makes them flow much easier from the bottle, its something I learned here on RCU.
And if you put the cup with the mixture in icy water it slows and extend the working time.

I write the mixing time on the cup before I pour the resin and hardener into it, its important because that’s how I manage the whole process without getting into cured epoxy while working.

I mix it also on tower catalogs, that’s what they are for.

as for brands i use tower, will try GP next, they are all the same, i choose by the comfortable package.
towers epoxy work time wasn't reliable, NHP was but i cannot find them any more.

Alex