OK--Thanks--

I'll get the borate up higher. If you said 40# puts me at 18 ppm. Then I need to add 85# to get to 50ppm. I can get it at my local Farmer's Coop in 50# bags (It's used to supply trace Boron mostly for Alfalfa, I think). BTW, Baking soda is usually available at Coops too in 50# bags.

One bit of clarification--I knew I was close to scaling conditions--I had understood that this would help preserve plaster from normal erosion. I know Calcium is essential for this, but does the Carbonate play any role in plaster preservation?

Charles