With a pointed bottle opener, pierce two holes in the top of the can. Place in a small saucepan and add enough water to reach three quarters of the way up the can. Bring to a boil and continue boiling on medium-high heat for 1 to 1 1/2 hours, adding water as needed to keep it at the halfway mark on the can. To test, pour a little onto a plate; when the color has turned light brown or caramel, it is done. Allow to cool before handling.