Easily Turn Baking Soda into Washing Soda in the Oven

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Washing soda, or sodium carbonate, is a common ingredient in laundry detergent. If you make your own cleaning products, you’ve likely added washing soda to some of them. Or you may want to make your own cleaning products but can’t find washing soda.

You can, however, find baking soda, or sodium bicarbonate, pretty much anywhere and “make” washing soda in the oven. Heating sodium bicarbonate breaks it down into sodium carbonate (Na₂CO₃), water (H₂O) and carbon dioxide (CO₂). You’ll be left with sodium carbonate which will look gritty and contain fewer clumps than the finely textured baking soda it began as.

Is it washing soda yet? An optional test

Simply looking at the baking material should suffice in determining whether the transformation has successfully occurred but if you’re unsure, continuing to bake washing soda won’t harm it. If you’d prefer a more accurate test of doneness, weigh the baking soda both before and during baking.

In 2010, Harold McGee, author of the classic On Food and Cooking: The Science and Lore of the Kitchen, wrote about baked baking soda in the New York Times. He said the resulting sodium carbonate will weigh two-thirds the baking soda’s original weight.

So if you are a detail-oriented scale owner:

1. Place your cookie sheet on the scale, weigh it and note the weight.
2. Tare the scale out, spread the baking soda on the cookie sheet and note the weight. Multiply the baking soda’s weight by 2 and divide by 3. That is your target weight for the sodium carbonate.
3. After the baking soda has baked for an hour, place the baking sheet with the baking baking soda on the scale. Subtract the weight of the cookie sheet from the overall weight. You now have the weight of the transitioning baking soda. If this number is greater than the target weight, continue baking.

You may find weighing helpful if you decide to make much more or much less than the 3 cups called for in the recipe card below. A quarter cup will require less baking time, for example. And by using a scale, you won’t have to guess when you can turn off the oven—and conserve energy.

Label the jar

Although some recipes do call for sodium carbonate, such as ramen (which I now must make), I don’t want my family mistaking mine for baking soda or some sort of superfine table salt. I labeled the jar not only to avoid confusion but also because I love gluing on paper labels with wheat paste. (Rice glue, made out of leftover rice, also works.)

I save brown paper for these labels (and for gift wrapping). You don’t have to go full on pioneer days of course but baking the baking soda may motivate you to craft all the things.

Some washing soda uses

When cleaning with washing soda, wear gloves if you have them as it can dry and irritate your skin.

Laundry detergent. I first used washing soda to make liquid detergent similar to this recipe. It works well, costs less than store-bought and eliminates the giant orange plastic jugs. (Brightly colored plastics are not recycled.) According to Arm and Hammer, maker of washing soda, half a cup of washing soda added along with detergent will leave clothes cleaner and fresher.

Dish soap. When I first kicked plastic, one question I heard repeatedly was, “How do you wash dishes?” This was back in 2011, before the dawn of fairly easy-to-find dishwashing blocks. So I made my own. And as I write this, only a sliver of my dishwashing block remains so I’ll make a batch of dish soap this week. Go here for the recipe.

Scouring powder. Combine baking soda, salt, washing soda and dried citrus zest for a citrusy, effective scouring powder to clean sinks and tubs. It also helps remove rust from glass jars and lids. Go here for the recipe.

Dye fixative. Recently after dyeing cotton produce bags pink using avocado pits and wishing I had a fixative to make the color last longer, I realized that I had washing soda, which can be used to set dyes for natural fabrics. (And I also had baking soda…)

Before and after shots

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