One of the biggest pyro displays one can pull off on a river trip is something called a grease bomb. Using a hot fire, a good amount of bacon grease, and some water, the little (or big) pyromaniac in us all can come out and play.
When executed correctly, the simple ingredients hurl a massive fireball skyward, produce squeals of enjoyment from the peanut gallery, and show your group a safe display of what happens when you show complete disregard for that age old saying of "don't pour water on a grease fire".
**Warning this Instructable involves fire, explosions, bacon grease, and danger. If you'd like to do another project involving copious amounts of bacon grease with a much lower danger factor, check out How to Make Bacon Soap. Grease bombs can be very dangerous and should only be done by experienced bacon grease pyrotechnicians. When done correctly they are a real good time.**
Step 1: Gather Grease
On the river we collect grease from bacon. Trip guests love bacon - so that means that we're usually cooking up POUNDS of the stuff on each trip. Each pound yields about 1/4 to 1/3 of a cup of grease, so collect all the grease you can until you've got about 2 cups worth.
Any fatty meat will produce good grease, so try rendering grease from different sources and see which produces the biggest fireball. (Anyone who can speak to the flammability of different types of animal fats please speak up).
After cooking the bacon, I let the grease cool. Then, I place a coffee filter on top of a non-breakable sealing container and pour the grease through. If your grease has little bits of meat in it, it won't work as well and it will splatter and sputter as you heat it. The coffee filter takes out all of those impurities and results in wonderful amber clear grease.
Step 2: Prep the Burn Area
Think hard about grease bomb placement. Grease bombs produce a giant fireball that rockets towards the sky. You'll need to pick a site that is not only clear of flammable objects around it, but also free of branches and trees above it.
If you have any doubts about your site, think things through, take the time to find the right place, and do things right. Ideally the grease bomb would be set off in the middle of an empty parking lot. Beaches afford the same level of safety and are good candidates. You should be thinking along these lines, not those of - yeah - the courtyard of my apartment building looks like a good place.
In most cases a grease bomb is a fun thing for you and other people to enjoy. That means onlookers - lots of them - so make sure that they are all at a safe distance from the fire (25 feet minimum). If they are too close they'll not only be in harms way, but they'll experience an unfortunate byproduct of a grease bomb - noncombusted grease that rains down from above.
Step 3: Boil Grease in a Can Over a Hot Fire
- Is there a fire ban in my area/state?
- Is there anything flammable around me?
- Is my burn site non-flammable? And, if not have I hosed my burn site down with water?
- Is there anything above my fire which could burn (trees awnings etc...)
- Is the peanut gallery located a safe distance away from the fire so they don't get burned?
You'll want to use a blower, fan, boat pump, hair dryer or billows to make a really hot fire. Regular BBQ coals make great fuel, they just need a little oxygen to reach their full potential. For more extensive coal lighting instructions check out: Best Way to Start BBQ Coals.
Once the fire is burning really well put away the blower, pump or what have you. Next, pour the grease into a suitably sized can for the amount of grease thats been collected and place it right inside the pile of coals. Sometimes the fire is hot enough to heat the grease on the grill itself, but I've found that direct heat from the coals works best.
Heat the grease until it's boiling and watch it closely.
During this time, duct tape a second can onto the end of a long pole or stick. Old boat oars work particularly well - they are about 10 feet long and allow the master of ceremonies (grease igniter) to be at a safe distance from the action.
Finally, build a small barricade using whatever you have around. On the river we use our dry boxes - old WWII boxes that the military used to ship ammunition and generators to the front. You'll want to use this barricade to help hold the oar in place over the fire as well. It also creates a nice hiding spot for the grease igniter to hide behind when the big moment comes.
Step 4: 1, 2, 3 Ignition
First it will just bubble a bit. Then, any impurities present in the grease will begin sputtering and spitting small bits of grease out of the can. Chances are, they will fall into the fire below and create small grease fires around the can.
This is a good thing.
Once the fire is burning around the grease can itself, and ideally, on top of the actual grease, it's ready for ignition. (See 5th photo below).
Using the oar cantilevered over the barricade, extend the can of water duck taped onto the end of it and move it into position directly over the can of flaming grease.
Do one more safety check before asking for a count down and then confidently pour the water out of the can on the oar and into the boiling can of grease below. The grease bomb will ignite as soon as the water touches the grease.
Experiment with emptying out different amounts of water onto the grease in order to get different size/multiple fireballs. The more grease you have, the more times you'll able to set the bomb off. Each fireball seems to consumer around 1-2 cups of grease depending on how much water is poured.
Step 5: Extinguish the Fire and Marvel
This grease bomb was done during June of 2008 in Oregon - a time when thousands of forest fires across the west coast were burning out of control. As a result, we exercised every possible fire safety, stood by with hoses and fire extinguishers (as you may have learned by now, water on a grease fire doesn't work so well), soaked the lawn down before and after we ignited the grease bomb and kept close watch on our proceedings.
At the time, there was a fire ban in California, but not in Oregon, and so we deemed it safe to proceed. If there was a fire ban would not have done this. Forest fires are the real deal and cost not only loads of money, but endanger many lives. Take fire bans seriously and help prevent further fires!
Use good sense when making a grease bomb. Don't hurt yourself, or those around you. Hot fiery grease is fun to look at, but not fun to touch - it will burn you very badly. Do this at your own risk and be safe.