How do I loosen a shower drain cover that seems glued down with gunk?

Nine times out of ten with tiled showers, the installer got sloppy and let thinset or grout squeeze right up into the rim, and years of dried soap scum finished the job. You're completely right to stop prying against the tile with a screwdriver, though. That's the fastest way to crack a piece of glazed ceramic and turn a five-minute cleaning into a weekend retiling nightmare. Instead of levering from the outside edge, try pulling straight up from the center. Grab an **Allen wrench** (L-key) that fits thru one of the slots. Feed the short leg down into a hole near the middle, rotate it 90 degrees so the hook grabs the underside of the grate, and clamp a pair of Vise-Grips onto the long end sticking up. That gives you an instant, rock-solid T-handle to pull vertically without ever touching your tile. Before you yank on it, take a utility knife with a fresh blade and score heavily all the way around the metal rim. You want to slice through whatever thin film of grout, dried mineral crust, or ancient silicone is bridging the drain body and the plate. If you suspect heavy calcium scale, soaking a rag in warm white vinegar and draping it over the drain for an hour will soften things up considerably, but mechanical persuasion usually does the trick faster. Once the perimeter is scored, pull upward steadily on the Vise-Grips with one hand while lightly tapping the metal grate with the plastic handle of a screwdriver using your other hand. The light vibration is usually all it takes to shatter the brittle bond holding the edges down, and the whole plate should just pop right out.

Before you go hauling on it with locking pliers, have you completly ruled out that the second hole isn't hiding a sheared screw?

It's super common for cheap brass or stainless screws to snap off flush beneath a layer of gunk after sitting in damp crud for a decade. If the head popped off for the previous owner and the threaded shank is still locking the plate down, pulling straight up is just going to warp the metal or crack the drain collar.

Take a dental pick or a small nail and probe down into that "empty" hole first. Make sure it acutally passes thru cleanly before putting heavy upward force on it.

Total newbie here, but if that second screw really is snapped off flush down there, how do you actually get the threaded part out without wrecking the drain? Do you have to use one of those tiny screw extractor bits, or is the piece underneath too fragile for that?

I have a guest shower doing the exact same thing and I'm terrified of breaking whatever the screw anchors into. Is that part easy to fix if the threads get stripped, or does that end up meaning tearing into the floor?

Regarding your concern about the metal finish, you really need to identify the exact metallurgy before applying any descalers, becuase while standard 304 stainless or electroplated chrome can tolerate mild acidic exposure, an oil-rubbed bronze or matte black fixture is often merely a delicate lacquer or PVD layer that will etch almost immediatly. Furthermore, if the obstruction is truly cured Portland-based thinset rather than typical calcium carbonate scale, household vinegar simply lacks the ionic strength to dissolve that silicate matrix, so you whould be much better off dabbing a warm solution of sulfamic acid directly along the seam with a cotton swab, wich specifically breaks down the cementitious binder without eating your brass sub-structure.

Hit it with a heat gun on low—a Wagner Furno or even a decent hair dryer works. alot of tile setters slap 100% silicone like GE Silicone II under the strainer flange to keep it from rattling, and mixed with mineral scale, it basically acts like concrete. Warming the grate expands the metal just enough to fracture the crust and softens any old silicone or dried soap wax. Just keep the heat moving so you don’t warp the ABS or PVC clamping collar underneath (most likely an Oatey 130 series or Sioux Chief 821). Two minutes of heat and it’ll pop right out.