Once the bacon has given up the bulk of its greasy goodness, remove bacon and pour grease into a small sauce pan. Simmer grease on low heat until it stops steaming. This will drive the water from the fat and allow for a better burn. This can take several hours, so be patient.
Essentially, we are rendering the bacon fat and creating tallow (beef) or lard (pork).
Two noteworthy points.
If you cook too fast, the grease will burn; it will still work in our Man-dle, but it may smell "off".
If you stop too early, it will still work, but the Man-dle may smoke and sputter a bit more than normal.
Do you see what happened there. Even if you aren't patient and don't follow the directions, the Man-dle will still work perfectly fine! Can this be any more Manly? Nope!