I've always made tortillas using the instructions on the bag of masa (Bob's Red Mill brand), which uses 2 cups of masa for 1-1.5 cups water. This...

Just to give an update, I ended up just adding more masa until the dough felt right. After letting it sit, it did seem to become a lot firmer. In any event, my tortillas came out great.

Another question though - it was a little unclear to me whether the recipe instructed to add the water to the masa or vice versa. I've done it both ways in the past, but I'm wondering if it makes a difference.

Anecdotally, I do think brands make a difference, as does my local weather and how long I let the dough sit before balling. I usually add most of the water, let the dough sit, then add a dash at a time to adjust as needed. The resting time might also come into play -- Happyolks talks about resting up to 2 hours, Bobs says about an hour. How much gets absorbed and/or slight evaporation could depend on resting time. Again, anecdotally, my dough seems to need more water the longer i'm resting it. But I'm lazy about plastic wrap and tend to go old-fashioned with a damp teatowel to cover, so I may have more accidental evaporation than most.

On the nerd-alert side of things: there are studies of this kind of thing! A 1994 article breaks this all out, but one interesting take-away is that it's not as simple as medium-grinds absorbing more than coarser-grinds. Instead, it comes down to both the grind level and the cooking time ( -- the processors' cooking times, not yours as the chef):

"The effect of grinding was greater than the effect of cooking when corn was cooked for less time (20 min), [...]. On the other hand, the effect of cooking was greater than the effect of grinding when corn was cooked for longer periods of time (55 or 80 min),[...]" [article avail at: bit.ly/M1Wcui ]

If the above is right, it seems to me that brands could vary considerably. Grind level alone won't tell you how the ideal amount of water to add. You'd also need to know cook time, which seems very brand-specific and I'd wager that info isn't readily available.

i.e. one more reason not to bother measuring! vindication!

My reading on the posted recipe is, add water to the consistency you need. Maybe the brands of masa differ that much -- ?