Hoppy, I double checked my 4dKH solution against my test kit and it was fairly close (So. Cal. is basically a big desert, so not much water was absorbed, I guess). I also used a very accurate scale for the 6g of sodium bicarbonate when I made the solution.

Anyway, I came out at 5 dKH with my test kit ... added a little distilled water and came up with 4dKH on the next test. I would think that, if anything, you would end up with less than 4dKH if any water was absorbed inte sodium bicarbonate, so this was a little confusing to me. Anyway, I'm close...