I'm making my second batch of cider ever (despite homebrewing beer since 2009). I'm using 3 gallons of Gravenstein juice purchased frozen last fall from a local orchard. The last time I made cider, which was a couple years ago I think, I added yeast (Fresco), campden, and nutrient to the juice, fermented it at a controlled temp, kegged, and enjoyed it.
For this batch my LHBS encouraged me to test and adjust the acidity, and sold me a small test kit. They recommended tartaric acid (which they sell in granular form), so I bought some. I tested the acidity -- that was fun. Something new to measure! But I am having trouble figuring out how much tartaric acid to add. Should I add, say, a tablespoon, stir, and then test again?