I’m using the new Alumilite plus resin because the sturdiest/hardest tray I’ve ever made was with the regular casting resin. I tried this one because I want the non- yellowing aspect. But I can’t get it to harden fully, it’s bendy and not tacky. I’m trying to make trays but they’re too soft after days! I’ve tried leaving in hot garage, 80- 90 degrees in Memphis. I’ve tried putting in my home to cure, around 75 degrees and still bendy. I don’t make the trays too thick definitely no more than a quarter of an inch. Two last details that are important are that the best tray that I made was back in March when it was cooler in my garage and I used the excess resin to make large pendants, but they hardened! These pendants are about 2.5 x 3 inches and I’m making them in the hot summer heat, using the excess resin from the trays! So, why do they harden and the trays won’t? Also, I use graduated cups and I stir for 3 minutes until clear .
Okay let's go over your process to see if we can pinpoint what went wrong and fix it.
First it sounds like you measured by volume and not weight (I do it that way myself). Were you careful to be sure to use a 1:1 ratio?
You said you mixed for 3 minutes so that sounds right and you noticed a color change which is also good.
You said they're thin, how thin are they? I made a 1/4 thick sun-catcher with the Amazing Clear Cast Plus and it hardened just fine with no bending or flexing at all. Now I had to rebuild a mold box last week and I had the old formula Amazing Clear Cast as a bottom layer and it was very thin and it did bend but it was under 1/4" thick. You could almost say it was 1/8".