Reader Ahu Shahrabani emailed last week to suggest that I cover By the Ounce, the wine bar that pops up at 6 p.m. in the café part of Bouley Bakery. “They have an extensive wine list and an array of tapas and even selection of caviar. I stopped by tonight and bought a four-ounce taste of a delicious 2008 Chateau Miraval ($4.50!). And the best part is they are open until midnight every night of the week except Sunday. I don’t think many people know about it, and I’m grateful something has opened up that stays open later. Brandy Library is great but not exactly as mellow, and I’m not a huge fan of the layout/set-up of Vino Vino. A great spot!”

It’s certainly true that for a wine-loving neighborhood—just look at all the great wine stores!—Tribeca could stand to have a few more wine bars. (The Tribeca outpost of Terroir, opening next to The Harrison this spring, will help.)

So I visited By the Ounce last night…. I had been in the café space before, and not much changes after 6 p.m., although four tables had long tapered candles and votives soon appeared on the others. Bouley and I don’t share the same taste in décor—don’t get me started on the scrunchy, tentacle-like lights dangling upstairs at Upstairs—but the room is comfortable, especially in contrast to the daytime; the chairs are padded; and the vaulted ceiling and large windows are lovely.

There are 20 wines by the glass, not including Champagnes and dessert wines (or “stickies,” as an Australian friend calls them), each of which is sold by the ounce, half-glass, or glass ($6.50–$23). I ordered a glass of a 2002 Veleta Tempranillo ($12). A much longer list of bottles, presumably the same one as at Upstairs and Bouley, is also available. One side of the food menu is all sold by the ounce: caviar, shrimp, charcuterie, and cheese—including raclette and fondue. The other side lists small plates such as tuna tartare ($10), braised veal meatballs ($10), gnocchi with sausage ($11), and even a skirt steak ($13). I didn’t order food—I had plans afterward—but a nearby group of women was very much enjoying their fondue. There were also people who were eating food from the other half of the operation, bringing cafeteria images to mind and spoiling the atmosphere just a little. I assume that this is less of an issue as the evening goes on.

I’m not sure how to put this, but…. How can service at Bouley establishments be so hit-or-miss? I’ve had amazing experiences at Upstairs and the Bakery, and I’ve had incredibly frustrating ones. (I haven’t been to Bouley proper yet, but I recall the old, fancy Bouley Bakery fondly.) And sure enough, my time at By the Ounce was like riding a roller coaster, ups followed by downs. Maddeningly, every step—determining whether I could seat myself (yes), getting a menu, ordering wine, receiving the wine, getting the check—took much longer than it should have. On the other hand, when the wine finally arrived, I learned that it had been delayed because the waiter was decanting it. (He didn’t want me to have to “eat it and drink it at the same time.”) In another nice touch, as I was leaving, another staffer told me I could take the laminated coaster—it was a copy of the Tempranillo’s label, in case I wanted to track down a bottle. Also to its credit, By the Ounce accepts reservations, particularly handy for groups.

The bottom line? Yes, By the Ounce is a great addition to the neighborhood. But as with Upstairs and the Bakery, consistency is an issue. Maybe the trick is to have a glass of wine before you go.

By the Ounce is at 120 West Broadway (bet. Duane and Reade); 917-237-3207, davidbouley.com.