I had isomalt crystals that I'd bought a few years ago, otherwise, I'd have bought the nibs. But it wasn't hard at all and I kind of like the idea of trying sugar and corn syrup even. However, my "ice cubes" came out just slightly yellow.
I used a cooling bath and cooked to the exact temp. I'm thinking my thermometer may be a bit off? I didn't calibrate my thermometer.
Could the age of the crystals have been a factor?