Quoted:
Not to hijack, but the oven cleaner takes the varnish right off the wood, huh?
I've got an AK that I wouldn't mind darkening up the handguards some.
Yep, in about 5 minutes. Just be sure to scrub it off with lots of water. I use rubber gloves and a water hose outside.
Sometimes it may take a second application, but that's about it.
Don't leave it on for extended periods as it is a caustic and if left on for long periods, will do damage to the wood.