Sorry - confusing my pentas, decas tetras etc. It's all greek to me.:rolleyes: Thinking metaborate. More greek.
I dunno how it's done commercially but I'd presume if there's excess water the deca will form. Commercially it's cheaper to ship 3/4 ton of penta than 1 ton of deca and deliver the same amt. of borate. Therefore one might be led to suspect there is some contamination of deca with penta regularly since it's in the system.
"You still have to weigh the crystals to make any use of them".
Don't think you meant one could tell the difference by weighing the crystals. If you did I don't see how. Naturally one weighs crystals - how else?
Is this one of Plato's Dialogues?