Pamela Marcum at Polysciences notes:

>>When I lived in the Bay Area, Foster City CA, we found the tap water to at
pH 8.3 to 8.7.  If I tried to blue sections it was a joke so we gave up and
just used the water as the bluing agent.  Now I am outside Philadelphia and
the water is closer to pH 7.0 -7.8 and I need to blue again.  so indeed
checking the pH of the water in your area is important.  I found in my
travels as a technical person that the pH of the water varies in all areas
of the country.<<

Hard water - with dissolved calcium bicarbonate - has a high pH and will blue 
hematoxylin quite effectively. I've seen this in New York City and in Hot 
Springs, Arkansas, among other places. Scott's bluing solution began as an 
artificial tap water. From my notes:

Scott SG (Oxford). On successive double staining for histological purposes— 
preliminary note. Journal of Pathology and Bacteriology 1911-1912: 16,390-8. 
Scott notes that "As tap water varies in constitution from place to place, and 
even the alkaline tap water of Oxford from the oölite Cotswolds requires ten 
minutes with occasional changes for safe removal of acid, the artificial 
substitute mentioned above has been introduced." Dr. Robert G. Wyllie in 1970 told me 
that this bluing solution was widely used in Australia, apparently introduced 
by Oxonian histologists nostalgic for the tap water of their homeland. Wyllie 
introduced this bluing technique at Johns Hopkins, using the term Scott's 
solution, and Gary Gill's publication popularized both the term Scott's solution, 
and the solution itself.

Scott’s original formula (which Gary Gill simplified) was

potassium bicarbonate 2.0 g
calcium chloride dihydrate 0.5 to 0.75 g
magnesium sulfate heptahydrate 20.0 g
water 1000.0 mL

Bob Richmond
Samurai Pathologist
Knoxville TN