I am going to see how long it takes to air dry a 4" thick slab of black walnut in the upper part of my barn which is very dry and gets incredibly hot during the summer. The ends have been sealed to reduce further cracking. I have a similar much longer piece air drying in the much cooler lower part of the barn. I am checking the moisture content percentage, and write it on the wood with the date. I will do this every couple of weeks until the moisture content stops dropping.