The most common fix people reach for first — tweaking retraction distance and speed — is usually the least likely cause. Work through these in order; most stringing problems resolve at step 1 or 2.
PLA absorbs moisture from the air over weeks, even in a closed room. Wet filament vaporizes as it hits the hot nozzle, creating tiny steam pockets that push out fine strings between travel moves. This is the cause behind the large majority of stringing reports on the A1. Dry PLA at 50–55°C for 4–6 hours before testing anything else. If stringing improves even partially, moisture was a real factor — dry a full cycle and retest.
A1's default PLA temperature (often 220°C) runs slightly hot for a lot of PLA and PLA+ blends. Try dropping in 5°C steps down to 200–205°C and reprint a stringing test — a small temperature tower is the cleanest way to isolate this. Too-hot PLA stays runny during travel moves, which is exactly when strings form.
A partially clogged or worn nozzle changes flow characteristics in ways that mimic classic stringing. A hardened steel nozzle swap does not fix stringing on its own — that upgrade is for abrasive filaments like carbon-fiber blends, not for oozing. If you've swapped nozzles and stringing didn't change, that confirms the nozzle wasn't the cause.
If moisture and temperature are both ruled out, run Bambu Studio's built-in retraction calibration test before manually guessing values. Blind manual tuning here usually just masks a moisture or temperature problem rather than fixing the underlying cause.