Exploding Caramel?

For our before Christmas dinner snack, the kids planned sliced apples and caramel dip. I tried out a neat idea that a girlfriend shared with me. I took a can of sweetened condensed milk, put it in a 6-quart pot of boiling water, and cooked for 3-hours. When I opened the can, we had a delicious caramel.

Here's the problem: I just went to Borden's website and it warned: "Notes: For safety reasons, heating the unopened can (an old cooking method) is NOT recommended." OOPS!

Instead, they recommend:
OVEN METHOD: Pour 1 can EAGLE BRAND into 9-inch pie plate. Cover with aluminum foil; place in larger shallow pan. Fill larger pan with hot water. Bake at 425º for 1 hour or until thick and caramel-colored. Beat until smooth.
STOVETOP METHOD: Pour 1 can EAGLE BRAND into top of double boiler; place over boiling water. Over low heat, simmer 1 to 1/2 hours or until thick and caramel-colored, stirring occasionally. Beat until smooth.
MICROWAVE METHOD: Pour 1 can EAGLE BRAND into 2-quart glass measuring cup. Cook on 50% power (medium) 4 minutes, stirring briskly every 2 minutes until smooth. Cook on 30% power (medium-low) 20 to 25 minutes or until very thick and caramel-colored, stirring briskly every 4 minutes during the first 16 minutes and every 2 minutes during the last 4 to 10 minutes.

I'll follow these directions next time!