I am changing my kitchen cabinet knobs but do not wish to change all of the hinges which are polished brass. How I can give them an antique finish? Thanks
That polished brass has a clearcoat finish on it to keep it polished. If it didn't, it wouldn't shine. Believe me.
Getting the clearcoat off completely will be nearly impossible.
If you want to try, I suggest trying with one hinge and boiling it in an old pan for a while.
If it's going to come off at all, that should start it.
Once you get it loosened, then some steel wool should tell you if it will all come off. If the hinge is not solid brass, you will also find out what it's really made of.
Then go to a good hardware store and ask them what you can use to darken brass. There are chemicals that will do the trick. Even household chemicals like ammonia might work. I am not up on my chemistry. The hinge will also just naturally darken to brown over time without the protecting coating.
By the time you go through all this you may decide it's a heckuva lot easier to recycle your old hinges to somebody who wants polished brass and buy new...Or make a trade!