I think you are all missing the point! Ammonia is a weak base and a lot of it will have to be used to increase the pH. The second point that I'd make is that alkali metals eg K, Na are a common component of clays and glasses and thus the small quantity of inexpensive sodium hydroxide required to raise the pH will have no perceivable effect. Why stuff around with with a volatile, expensive, weak bases when you don't have to?