Crap. My welding glass is only #10 (I took it out of the hood to be sure).
According to NASA, #14 or higher is required.
And in a quick glance through #10, it does feel uncomfortably bright. One YouTube video suggests if you can see outlines of trees & buildings silhouetted against the daylit sky, they're not dark enough. You definitely can with #10.
Another option is pull the other #10 from my small welding mask and layer them. With effectively #20, the disc of the sun is dimly visible.