Oh yeah--1979 was a good year at Tr Green. We used powder blue and her cheaper scaggy little sister "powder gray" (larger particles). But it did not suspend well even with major hydraulic-motor-powered paddle agitation shaft through the center of the tank. Plugged a lot of filters. Left a chalky residue on everything we sprayed. Release of nitrogen was very slow--I think--or maybe never.
We solved the fert burn problem eventually--dropped the potash, and reduced the urea nitrogen in hot weather. I remember changing the fill charts when the temps went over 80 and even less at 85 and still less at 90.