The Joy of Grease: How to make soap out of what’s sitting in that soup can on the back of your stove

There’s a tin can on our kitchen counter that no one goes near, filled with congealed bacon grease. It’s been collecting for months, and I really don’t know what to do with it. Except I DO know and just haven’t gotten around to trying what everyone alive in any century prior to ours would have done: make soap from scratch.

The internet is filled with how-to’s on this ancient art that every housewife once knew intimately. It’s a simple formula that you may even have experimented with in high school chemistry, adding a strong acid (sodium hydroxide) to a base (fat) to create a reaction called saponification. Any kind of fat will work, from beef suet to pork lard, or vegetable oils alone or in combination.

Truly committed DIY soapmakers make their own lye (sodium hydroxide) out of hardwood ash, boiled or steeped in rainwater. I like this concept as it uses “waste” products that most people throw away, like ash and leftover grease. Still, because this is my first time making soap, I opt for store-bought lye, with its known-quantity potency: it’s comes with a corrosive symbol on its label, like chlorine bleach, and is also used to clean drains. I plan to pick up rubber gloves and a face mask while I’m at the hardware store, out of respect for my lungs and skin while the lye does its work.

It seems that commercially-made sodium hydroxide is available at only one hardware store in the city, a nifty Home Hardware in the Burnside Industrial Park where I also bought maple-tapping supplies a few years ago.

The cashier tells me they get a lot of folks in to buy this stuff, and he hopes they’re all soapmakers; I find out later lye’s one of the ingredients in homemade crystal meth. Jeepers!

Back at home, the first step in my soap-making journey is rendering the bacon grease (basically, boiling it in several rounds of fresh water to remove impurities, with cool-down time in between boilings to allow the fat to congeal so it can be lifted right off the dirty water). It’s full of burnt bits and other grit that can be poured off or filtered out through a sieve or cheesecloth. The snowy back step is the perfect spot to allow my pot of fat to cool down between boilings.

I worry I won’t be able to fully get rid of the smoky bacon fragrance of the fat, but since I’m not planning on selling this batch of soap to a boutique, I’m not too concerned. I do add a dollop of regular commercial pork lard left over from Christmas baking so I’ll have more than just one measly cake of soap when I’m done.

I’ve already visited Valu-Village in search of a dedicated soap-making pot; once you start heating lye, you don’t want to make anything edible in that cooking vessel ever again.

After the rendering process is complete–I’ve boiled it about five times–my fat is looking a lot whiter and cleaner. I pull out a candy thermometer I’ve never used to make candy with, and melt the grease one last time, keeping it at a temperature of 120 degrees F.

It’s a nice day out, so I decide to take the lye outside. I mix 10 teaspoons of the powdered chemical into a cup of cold water. It’s amazing how hot the side of the measuring cup gets once the mixing begins– it’s easy to get burned. Using the candy thermometer again, I watch the temperature of the lye water drop until it’s about the same as the fat: 120 degrees. At this point, I add the acid mixture to the pot containing the fat and stir vigorously for five minutes. You’re looking for the soap to “trace”, that is, create a vanilla pudding kind of viscosity behind your spoon as you stir, indicating “doneness.”

My kid is keen on making this into cinnamon soap, so we dump a tablespoon or so of the spice into the mix. I have an old loaf pan ready–some soapmakers recommend lining it with parchment or wax paper, but I just greased mine–and pour the soap-pudding in. I wrap it in a plastic bag, and cover the pan with an old towel, said to help with the ongoing saponification process as the mixture hardens.

The next day, we eagerly unwrap our creation and are greeted with a solid rectangular block of soapy goodness. I can’t smell any cinnamon, but it’s definitely soap now, not bacon grease. I cut it into wedges and give it a spin on my hands in the kitchen sink. I have to admit, there’s a bit of greasy residue left on my skin after the wash, so likely something went astray in the reaction. On the whole, though, I’m pretty pleased at how easy it was to make soap at home.

If you, too, have a greasy soup can sitting on your counter but you’re not keen on making soap out of its contents, here are a few other uses for grease:

1. Oiling rusty door hinges

2. Greasing your bike chain–I use an old toothbrush for this purpose.

3. Polishing leather shoes–use grease in moderation and stay away from dogs!

4. Fresh grease can, of course, be used in cooking. Pie crusts, onion frying, greasy winter fry-ups, the possibilities are endless. I make spaghetti carbonara by cooking a few slices of bacon, then adding minced garlic to the hot fat–grease and all gets added to the pot of cooked spaghetti with a scrambled egg and some Parmesan cheese on top. Yummers!

If you’re worried about the health effects of consuming moderate amounts of animal fats, women’s health advocate Dr. Christiane Northrup reminds us that our ancestors regularly ate bacon grease and suffered far lower rates of heart disease than we do. Of course, they generally exercised more– we should be doing that, too!

Whatever you do with that soup can, I wish you the joy that comes from making useful that which others find useless and throw away.