Every erev shabbat we make coffee ahead of time, and enjoy iced coffee on shabbat morning. I've always loved iced coffee. I had read in several of my regular culinary sources that the best way to brew coffee for iced coffee was to just combine cold water with the ground coffee and let it sit for twelve hours. We decided to try it that way this shabbat. Being married to a scientist, we couldn't just leave it at that. We also had to do a hot brew so we could compare the two and see which was in fact better.
The next morning, we each independently did a taste test and arrived at the same conclusion - the hot-brewed iced coffee was immensely superior! The cold brew was very acidic and overly-assertive. Not all that pleasant a taste. But the hot brew was nice and smooth and of a good flavor. It's possible that twelve hours was too long for a cold brew, so it developed too high a pH. We're not sure. But in any case, we're sticking with hot-brewed iced coffee.