"...In an objective rather than subjective way, I mean ... can I assume that my soap is cured when its weight (total of all the now cut pieces) reduces by about half the water weight (about 115 grams)? ..." Cure is not just about water evaporation, so the strict answer is "no." It's also about improvement in lather quality, skin feel after washing, and longevity. I don't know how you can determine some of these qualities in an utterly objective way. Even commercial soap makers don't have that all figured out. It is true that many soaps made with a blend of fats (and thus a blend of fatty acids) are going to be cured enough in 4-8 weeks to please most people. That also happens to be about the time when the weight loss slows substantially, so measuring the rate of weight loss is a simple, fast way to monitor soap. But this rule of thumb that does not invariably hold true -- a slowing rate of weight loss doesn't always mean the soap is sufficiently cured and performing at its best. The soap that taught me this fact was a soap very high in lard (stearic and palmitic acids). It did not lather well a month or two after making, but was a very pleasant soap to use at 1 year. If I decided weight loss was the only basis for determining it was sufficiently cured, the soap would have ended up in the trash. It almost did anyway, but I'm glad I gave it a final chance to prove its worth.