If you’ve ever poured what you thought was the perfect batch of handmade soap, only to find a mysterious white film on top the next day, you’re not alone. That powdery layer is soda ash, and it’s one of those little quirks that every soapmaker encounters at some point. It doesn’t ruin your soap, but it can be frustrating—especially when you’ve put so much effort into getting the perfect colour and finish.
So, what exactly is soda ash? Why does it appear? And most importantly, how can you deal with it? Let’s break it down.
What Is Soda Ash?
Soda ash (sodium carbonate) forms when unreacted lye in fresh soap meets carbon dioxide in the air. This reaction creates a harmless, chalky film that sits on the surface.
It doesn’t affect the way your soap works—your skin won’t even notice it—but it can dull vibrant colours or make a smooth, glossy top look a little dusty. Some soapmakers even embrace it, letting it add a rustic, handmade touch. But if you’d rather keep your bars pristine, there are ways to prevent and remove it.
Why Does Soda Ash Happen?
Soda ash is unpredictable, but a few things make it more likely to show up:
🌿 High Water Content – A higher water-to-lye ratio slows down saponification, giving soda ash more time to form.
🌿 Cooler Temperatures – If your soap cools too fast, the top layer stays reactive longer, inviting soda ash to settle in.
🌿 Pouring at a Thin Trace – If your soap is still very fluid when you pour, it may take longer to emulsify, increasing the chance of soda ash.
🌿 Air Exposure – Leaving fresh soap uncovered for too long gives carbon dioxide the perfect opportunity to work its magic.
How to Prevent Soda Ash (or at Least Keep It Under Control)
You don’t have to fight soda ash—just outsmart it. Here are some tried-and-true ways to keep it at bay:
✨ Spritz with Isopropyl Alcohol – A light mist of 91% or higher alcohol on the surface right after pouring can help prevent soda ash from forming.
✨ Cover & Insulate – Keeping your soap wrapped or covered for the first 24 hours reduces air exposure. A simple layer of plastic wrap can do wonders.
✨ Reduce Water Content – A slight water discount speeds up saponification and makes it harder for soda ash to develop.
✨ Keep Temperatures Consistent – Avoid making soap in a cold room, and consider covering your mould to help the soap stay warm as it sets.
✨ Pour at Medium Trace – A thicker trace means the oils and lye are better combined, reducing the risk of soda ash forming on the surface.
Oops, Soda Ash Showed Up. Now What?
Even with the best precautions, soda ash sometimes just does its thing. But don’t worry—it’s not permanent. You can easily remove it:
🌿 Steam It Off – A few passes of steam from a kettle or handheld steamer will dissolve soda ash like magic.
🌿 Rinse & Dry – A quick rinse under warm water followed by air-drying can restore your soap’s original look.
🌿 Wipe It Down – A damp cloth or paper towel works well for small areas.
🌿 Embrace It – Some soapmakers actually like the soft, rustic aesthetic soda ash creates. It’s a reminder that each bar is handmade and unique.
Soda ash is just part of the handmade soap experience—like unexpected swirls in a design or a fragrance that behaves differently than planned. It’s not a flaw, just a little personality. And whether you choose to prevent it, remove it, or let it be, your soap is still just as beautiful, nourishing, and thoughtfully crafted.
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