Play it safe NEVER use the last drops from your mix cup!
When calculating the amount of resin needed for a project, factor in 5% waste, this will be the epoxy resin stuck to the sides of the mixing cup, the mixing stick, ect. Epoxy resin by nature is inherently sticky and when you pour Part A in, what is touching the sidewalls of your mix container is pure Part A when you add Part B, it’s pure Part B touching that part. When you begin mixing, the material touching the sidewalls is not likely getting the same blending action as the material in the center of the cup, it’s critical to scrape the sidewalls and bottom of your mixing container to ensure you get as much material as possible into solution. You can go a step further and pour your mixed solution into another clean mixing cup and stir a bit longer, that will significantly reduce the odds of any unmixed Part A or Part B being in your final solution.