So then we should assume 30 days in the sun is no better than 30 days on a drying rack. How do you test for hardness and where does the number 38 come from?Tam said:I did a test this summer. This part of Texas was in a terrible drought and we've had like 90 days of 100+ temps...or something like that. Anyway, I took one bar and placed it in the full sun for a month and I kept the other bars inside. The ONLY difference was the bar that I let "bake" in the sun bleached out a bit, but as far as hardness...no difference. The soap was a CP with a 38 on the Hardness Scale.