a). not allow the blender to mix the lemons in the water for too long. About 4 seconds should be enough, just until the pulp is crushed and
b). do not let it sit, but filter it immediately into the jar that you will be using.
this book that drew my attention by its title: "Paletas: Authentic Recipes for Mexican Ice Pops,shaved Ice & Aguas Frescas", by Fany Gerson. And how could I not fall for it when it starts like this:
"The first frozen treats in Mexico were made with snow collected at the top of the Popocatépetl and Iztaccíhuatl volcanoes. At first the snow was carried down and used to refrigerate things like medicine and food, but later people realized they could pair the snow with sweet fruits to make luxurious frozen treats. "