I've usually used caustic soda diluted in water @ about 2 teaspoons to =
500mls of water.=20
Be aware! wear protective clothing and gloves, hat/goggles if overhead, = and, consider a face mask there are minimal fumes even at this dilution = and it's corosive in nature. Apply liberally with a well wetted sponge = and protect surrounding areas especially the floor and surrounding = metal/paintwork.
Treat as you would any other paintstripper, leave to work for 15-20 mins = before attepting any removal, look for blistering/slime. re-apply as = required. the 'mixture' keeps indefinately in a coffee jar or similar.
After successful stripping, wash wood with plenty of warm water or = consider using white spirit to ensure the grain doesn't rise or split. = leave to dry, consider what coating to use! :-)