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controlling soda ash handmade soap

Soda ash is the white, powdery substance that can appear on the surface of the soap and can detract from the finished look. While it’s possible to just live with the soda ash on handmade soap (or even love it), there are tried and tested solutions to completely avoid soda ash for those that hate it! In this blog post, we’ll explain what soda ash is, discuss how to prevent soda ash in your cold-process soap formulations, provide tips for removing soda ash from your soap… plus show you a few reason why you just might learn to love soda ash!

What is Soda Ash in Handmade Soap?

Example of glycerin rivers and soda ash on handmade soap
Soda ash , glycerin rivers & soda ash in the glycerin rivers – Arrie Knudtson

Soda ash on handmade soap is a common occurrence in cold process soap. It is a powdery, white residue that can form on the surface of the soap. Soda ash doesn’t harm the soap, but it can affect the appearance and texture of the finished product. Sometimes you’ll hate soda ash, while sometimes you’ll love it. Either way, understanding what causes soda ash is the first step in preventing it (or forcing it).

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Why Does Soda Ash Form on Handmade Soap?

Soda ash is a reaction between the sodium hydroxide (lye) used in the soap making process and the carbon dioxide in the air. As the soap cools and hardens, the carbon dioxide reacts with the sodium hydroxide to form sodium carbonate, which is the soda ash on handmade soap.

Several factors can contribute to the formation of soda ash on handmade soap. The temperature and humidity of the curing environment can affect how much soda ash forms on the soap. If the soap is cured in a warm, dry place, then the likelihood of soda ash forming will be reduced. However, if the soap is cured in a cool, damp area, then the chances of soda ash forming increase.

Example of attractive soda ash on handmade soap
Soda ash on buddha soaps, Activated charcoal color / scent geranium patchouli from Penny Krier

Another factor that can contribute to the formation of soda ash is the recipe itself. Certain oils and additives can cause more soda ash to form on the soap than others. For example, using high amounts of a single oil (such as coconut oil or olive oil) in your soap recipe can increase the likelihood of soda ash forming. I don’t know why, but I do know that it’s true because I’ve struggled with it myself.

By paying attention to the temperature and humidity of your curing environment, as well as adjusting your recipe, you can minimize the amount of soda ash that forms on your soap. In the next section, we’ll go over some tips for preventing and cleaning up soda ash on your handmade soap.

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How to Prevent Soda Ash on Handmade Soap

If you’re all to familiar with the unsightly white powdery substance known as soda ash (that gosh darn harmless but cosmetic defect on your beautiful handmade soap), here are a few things you can do to prevent soda ash from forming on your soap:

  1. Use distilled water – Hard water can increase the chances of developing soda ash on handmade soap, so using distilled water instead can help reduce this problem. Using distilled water also helps prevent DOS!
  2. Reduce the water content in your recipe – this is the number one best bet for “curing” soda ash on handmade soap! The more water you have in your soap recipe (and in your curing environment), the more likely soda ash is to form. Try reducing the water content in your recipe to see if this helps. I like to use 1:1 water:NaOH for my lye solution. There’s more information on this in my Go-To Vegan Palm-Free soap recipe and in this article on controlling trace.
  3. Cover your soap while it’s curing – Covering your soap with a lid or plastic wrap can help prevent soda ash from forming during the curing process.
    • Covering with plastic wrap as more effective than a towel or lid as it does a better job of preventing air contact with the soap – remember, it’s the carbon dioxide in the air that is half of the recipe for soda ash on handmade soap.
    • If you are using just a lid, or a towel, first spray your wet soap with IPO (Isopropyl alcohol). It will help evaporate the water on the surface, which will reduce the chance of soda ash developing from air that creeps in under the lid.
  4. CPOP (gel) your soap – when your soap goes through a full gel phase, the chances of soda ash are greatly reduced. I “think” (i.e. I’m guessing) that the heat in the process allows the excess water to evaporate before it can turn into ash. No idea if that’s right, it’s just a guess. Here are more details on the gel phase in cold process soap.

Tips for Cleaning Up Soda Ash on Handmade Soap

Preventative measures are great, but you’re probably here because you already have soda ash on your cold process soap! Don’t worry, there are ways to clean it up:

  1. Wipe it away: First, try wiping the ash away with a soft cloth or paper towel. Be gentle and careful not to damage the soap. This is more of “buffing” your soap vs. wiping. If it’s just a touch of ash, this MIGHT work. But the ash could also reappear.
  2. Mist with water: If the ash won’t budge, mist the soap with a fine mist of water. This will cause the ash to dissolve and wipe away more easily. And yes, could even run the soap under running water to wash the ash away.
  3. Use vinegar: Another solution is to dip a clean cloth in white vinegar and gently rub the affected areas. This will neutralize the ash and leave your soap looking clean and smooth.
  4. My favorite solution (water and IPO): First mist with water, then with IPO (isopropol alcohol). This always always works for me, and leaves the bars nice a shiny too!
  5. Use a Soap Planer: If you have a very thick layer of soda ash, you can use a soap planer to remove soda ash from your soap. This tool is designed to shave off the top layer of your soap and create a smooth surface. It’s important to use a gentle touch when using a soap planer, as you don’t want to shave off too much soap.

Learn to love soda ash on handmade soap!

If all else fails and you can’t remove the soda ash, don’t panic: It’s important to remember that soda ash won’t harm your soap or your skin. It’s simply an aesthetic issue. If the ash won’t budge, embrace the rustic charm of your soap with soda ash speckles! I sometimes try to FORCE soda ash on a few of my molds because it can be very pretty design effect.

Here are a few of my soaps where I was thrilled with the soda ash:

summer citrus blossoms 1024

See the white speckles on the purple petals? That’s soda ash! I painted the petals purple with a bit of soap batter to which I added some extra water because I WANTED soda ash!

spirulina mini soaps

Notice the lighter brighter tops on these soaps? Yup, that’s soda ash! After texturing the top of the loaf, I sprayed it with water and prevented a gel to ensure I would get some ash development in the nooks and crannies of the textured top.

Examples of Soda Ash (some to love and some to hate):

The following soaps are from some of our Soapy Friends over in my Facebook Group. I’ve got to tell you, having a group of soapy friends is so amazing! 1: I’m writing this post in response to a question from the group, and 2: since I didn’t have any photos on hand of soda ash under the “hate” category I asked the group to help. And, wow, just wow! Look at all of these great reference photos we now have! Soapy Friends FTW! Thank you all!

2 thoughts on “Controlling Soda Ash on Handmade Soap: Love it or Hate it (with 12 examples of soda ash on soap)”

  1. I will never imagined that some oils could make your soap to have soda ash. It’s true sometimes I like the soda ash on the soap. Have you tried using a steamer? I have and it worked for me. I steamed it before taking it out of the mold. Didn’t know about those tips. It happened to me once, there was soda ash inside the soap. Didn’t like it at all. Next time I get soda ash on a soap, I will try the tips you give here. You always give lots of tips. Thanks!

    1. I’ve never steamed my soap because I don’t have a steamer and if I’m putting a kettle on it’s for a cup of tea, not soap. Lol. Spraying with water and then ipo is simpler for me. And, since I use low water I don’t get ash aside from my testers that usually have air and not a perfect trace and insulation (since they are such small batches).

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