Testing for Washing Soda – The Failed pH Test and the Unexpected Discovery

I’ve been making my own laundry detergent for a few months now.  Our clothes are clean and soft, and we are enjoying both the money savings and the absence of perfumes and unnecessary chemicals in the wash cycle.

Many of the recipes for laundry soap use washing soda as an ingredient.  In my main recipe, I use baking soda.  Lately, though, I’ve wanted to experiment with washing soda to see if it might be a cheaper alternative and also if it might add noticeably to the cleaning power of my laundry soap.

As I was searching for where to find washing soda, I found many people were claiming to make their own washing soda by heating baking soda in the oven.  While I could find a general consensus that the baking soda would be heated for 1-2 hours in a glass (not aluminum, since washing soda is caustic to aluminum) dish at 375 to 400 degrees F until it turned uniformly from fine-sand white to a grainier, slightly greyer powder.

I wondered, did that really create washing soda?  Or just warmed-up baking soda?  Researching did not really help me until I found a scientific site with a formula for creating sodium carbonate (washing soda is 100% sodium carbonate).  In one of the steps of the formula, sodium bicarbonate (baking soda is 100% sodium bicarbonate) was heated until it released carbon dioxide and water, leaving – ta da!  – sodium carbonate (washing soda!).  However, the heating temperature in the formula was 300 degrees C, which translates to 575 degrees Fahrenheit.  Way too hot to be safe in a home kitchen, or with most kitchen dishes, pans, and ovens.  Downright dangerous, I’d say.

So, now I wondered if heating the baking soda at the lower temperatures for longer time periods would indeed create washing soda.  How could I tell?  Sure, it looks a little different.  But how could I be more certain?

I realized that washing soda has a much higher pH (much more alkaline) than baking soda.  So I decided to heat up a batch of baking soda and test the pH of the resulting powder.

To make a long story short, my pH test was fatally flawed.  I found out mid-experiment that my pH tape was not rated to test over 9.0 on the alkaline scale.  Washing soda has a pH of 11.6.  Baking soda is 8.4.

By the way, it’s that extra alkaline property that makes the washing soda a better water softener and cleaning agent than the baking soda.  So being more alkaline is a laundry detergent plus, even though it also makes the washing soda a hazardous chemical as far as it should not come in contact with skin and should never be eaten.  Don’t even taste it! Ok? Ok then.

But, I did make a really interesting discovery that made the experiment worthwhile.  Here is what I found:

The jar on the left is baking soda and filtered water.  The jar on the right is the “homemade washing soda” and filtered water.




Note that the baking soda did not completely mix.  It still has a thick layer of unmixed baking soda on the bottom of the jar, and this is after observing it and vigorously mixing it again.  The jar with the “washing soda” and filtered water is crystal clear and was only mixed once.

Thus I discovered that, at the least, heating baking soda dramatically increases it’s ability to dissolve in water.  Actually, that is one of the superior properties of washing soda: it is more soluble than baking soda (ie it dissolves in water faster and stays that way longer).

I do think I created washing soda in my oven, but still have not been able to prove it.  But I did discover the reason why I occasionally get a white powder on the clothes when I add baking soda directly to the rinse water, instead of taking the time to dilute it in water and dissolve it before adding it.  For some reason, the agitation of my washer must not be enough to completely dissolve and redistribute all of the baking soda.

As far as the costs?  In my particular experiment, including the oven heat, it costs 3 TIMES as much to make my own washing soda as to buy it in the store.  I have ideas on how to cut back on the oven heating costs, but for this little batch of “washing soda”, I would have been far better off to simply purchase it at retail.

For all the details of the experiment, and several photos, please visit our site for the full article Make Washing Soda From Baking Soda – The (Seriously Flawed) pH Test .

Here’s to scientific discovery,



Please note: Heat baking soda at home at your own risk! Washing soda (sodium carbonate) is a very alkaline, caustic chemical that can cause skin and tissue damage. It can also damage your aluminum pans. I don’t know enough about the properties and heating process to advise on the safety of heating baking soda. The Fat Dollar does not take responsibility for any damages if you try this at home!



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