The Dreaded Soda Ash

Gingersnap bars with heavy ash

If you make soap, you've probably had a few batches develop a whitish powdery layer on the tops. If you buy handmade soap, you may have seen this sort of thing. What is that stuff?

It's ... dah, dah, daaaah! ... soda ash.

What is soda ash? Conventional wisdom states that soda ash is sodium carbonate, which results from sodium hydroxide (lye) reacting with carbon dioxide in the air.

There may be other explanations for this phenomenon, though. In her book "The Soapmaker's Companion," Susan Miller Cavitch suggests that the powdery substance may just be dried soap. Glycerin, a natural by-product of the soapmaking process, attracts moisture from the air. Cavitch theorizes that the soap molecules closest to the surrounding air draw in moisture and then dry, forming tiny crystals. Her theory has been tested by a chemist, who could find no trace of sodium carbonate in the ash on her bars.

Beer soap with soda ash

Another idea is that soda ash could be minerals from the water in the soap collecting on the surface. This is one more reason to use distilled water for soapmaking, although I always use distilled water and still sometimes experience heavy ash. I have also experienced ash using beer in place of water.

Many factors can influence whether or not ash will form: temperature, batch size, fragrance or essential oils, humidity, soap density, or the soap recipe itself.

The origins of soda ash may be somewhat of a mystery, but one thing we can agree on is that it is harmless. (A thick, crumbly crust is another story - such a thing as that probably indicates lye-heavy soap.)

I think another thing that most of us soapmakers can agree on is that it is a total pain in the ash.

So, now that you kinda-sorta-not-really know where soda ash comes from, how can you prevent it from happening? I sometimes gently place a sheet of plastic cling wrap over the top of my soap after pouring it into the mold to prevent the surface from coming in contact with the air. This is fine if your tops are flat, but it doesn't work so well if you have textured tops. Another thing you can try is liberally spritzing the top of the soap with 91% rubbing alcohol after pouring.

Some folks don't mind ash. Soapmakers sometimes embrace it as part of the process and feel that it lends a rustic handmade charm to the soap. And soda ash tends to just wash off the first time anyone uses the soap, so it needn't be a huge concern to the soapmaker or the customer.

But it's just not pretty. And to the untrained eye, it can even look like mold or fungus (which it's totally not).

So let's say that you don't want soda ash. Let's also say that you get some despite your best efforts to avoid it. How can you get rid of soda ash once you get it?

This video by Soaping101 explains what soda ash is and offers up four methods for getting rid of it - alcohol, water, glycerin, and steam:



In the video, Soaping101 tries all four methods: spritzing the finished soap with 91% rubbing alcohol, dunking the soap in water, painting the soap with a bit of glycerin and colorant, and steaming the ash away. The conclusion was that while all methods removed some of the ash, steaming seemed to be the best bet.

Remember the photo of my Gingersnap soaps at the beginning of this post? I made that batch in September and it developed heavy soda ash. I had a couple of bars leftover and had never taken the time to try to remove the ash. The soap I make is just for me and my family, so I wasn't too worried about getting rid of it. A while back, someone on one of the soapmaking forums I belong to mentioned using steam to get rid of soda ash. Intrigued, I poked around the interwebs a bit more and found Soaping101's video. I liked the idea of using steam. Sure, you can slice the ash off, but then you mar the top (and waste a bit of soap). Rinsing with water can also mess up the tops. But a quick steaming would get into the nooks and crannies and it wouldn't interfere with the soap, which is great for textured tops, fancy peaks, or tops sprinkled with oats or seeds.

Since these Gingersnap bars had such heavy ash, I thought they would be good candidates for a blog feature and I decided to give the steaming method a try.

Holding bar over steam (l); After steaming (r)

All I did was simmer some water in a pot on my stove and then hold the soap over the steam. (The soap can get a little slippery, so I held it with a paper towel.) You could also use a tea kettle or a clothes steamer, whatever steam-errific thing you want. After a few seconds, the tops of the soaps looked a bit wet and the ash seemed to disappear. I let the bars dry on my curing rack for a few hours. Several days later, the soda ash was still gone.

(You may be wondering what the deal is with the yellowish parts in the photos above. I tried to swirl some gold-colored soap into the tops, but it didn't really work. I think I fiddled with it too much. I also wanted textured peaks, which didn't really work either. I still have the hardest time with that.)

So, I think in the future I will use the steam method to get rid of soda ash. It's quick, easy, and effective and it won't screw up the soaps.

Got any soda ash woes, my soapy friends? Does ash bother you as either a soapmaker or a customer? How do you like to get rid of it? Or do you prefer to just roll with the ash and keep it?