If you’ve tried your hand at homemade cold-process soapmaking, you’ve likely run into the dreaded “soap scar” known as soda ash. This white powdery residue and film can appear on top of or around your soap, especially with fresh batches, ruining the smooth appearance of your beautiful creations. Not only is it unattractive, but soda ash can cause issues with the feel of the bars, leaving behind a sticky, tacky surface. But don’t despair! While soda ash is a common problem many homemade soap makers face, there are several easy tricks you can try to battle soda ash. With some preventative measures, testing, troubleshooting, and recipe tweaking, you can fix soda ash and end up with perfect, gorgeous handmade soap bars every time.

What is soda ash and Why Does It Occur?

Soda ash, also known as sodium carbonate, is a white powdery deposit that can appear on cold-process and hot-process soap. It forms when lye reacts with the carbon dioxide in the air. Essentially, the high pH of the soap causes the oils on the surface to absorb carbon dioxide and convert it to soda ash.

Causes of Soda Ash

There are a few key factors that cause soda ash in homemade soap:

  • High humidity leads to excess moisture.
  • Temperature fluctuations during saponification
  • Fragrance oils and essential oils
  • Not enough cure time

Appearance of Soda Ash

You’ll know soda ash when you see it. It emerges as a white, chalky powder on the surface of soap, looking similar to efflorescence or salt crystals. Soda ash can also cause your soap to look frosted rather than smooth.

Issues Caused by Soda Ash

Aside from marring the appearance of your soap with crustiness and poweder, soda ash can cause other issues:

  • Sticky, tacky-feeling soap
  • Bars that easily crumble and fall apart
  • Soap that is too harsh or dries out the skin

The good news is that, with a few easy tricks, battling soda ash is simple!

Easy Ways to Prevent Soda Ash

While soda ash may be tricky to avoid completely, there are several easy techniques you can use to dramatically reduce the chance of those pesky white powdery deposits on your homemade cold-process soap.

Control Humidity and Temperature

Fluctuating temperatures and high humidity are common culprits causing soda ash. To prevent this:

  • Soap in a room with a consistent temperature between 75 and 85°F.
  • Set up fans to keep air circulating and moisture low.
  • Avoid soaping on extremely humid days.

Use a Water Discount.

One of the most effective ways to prevent soda ash is to use a water discount in your recipe. This means reducing the amount of water by 25–50% of the total water weight. Less water means less chance for bead-like soda ash to form.

Start by discounting 25% of your water and tweaking from there. Be cautious with higher discounts, which can accelerate the trace.

Add Sodium, Lactate, or Sugar.

Sodium, lactate, and sugar both help harden bars. Adding 3-5% sodium lactate or 1 teaspoon of sugar per pound of oils to your recipe can set your bars faster, leaving less chance for soda ash development.

Avoid Fragrances and Essential Oils.

Some soap makers notice more soda ash when adding fragrance oils or essential oils, especially floral and spice scents. Skip the scents entirely or use. 5 oz or less ppo if soda ash is an issue.

Insulate Your Mold.

Insulating your soap molds helps retain heat to encourage the gel phase. Gelling your soap bars can help decrease soda ash. Wrap molds in towels or bubble wrap after pouring to hold in warmth.

Gel Your Batch

If insulation alone isn’t leading to full gel, you can also actively force the gel phase by placing molds in an oven, on a heating pad, or in a hot car for 1-3 hours. Monitor closely and remove it once the soap batter gels.

Testing and Fixing Soda Ash

Even with preventative measures, you may still end up with a batch of cold process soap bars with soda ash. Before deciding to rebatch, plane, or otherwise “fix” your bars, start by testing them first. From there, you have a few options to eradicate soda ash and end up with an attractive handmade soap.

Perform a Zap Test

Before declaring your soap a soda ash casualty, check it with a zap test. This allows you to test if there is still excess lye or alkalinity. Swipe your tongue across a bar, focusing on a corner or edge. If it zaps or stings, your bars may just need more cure time.

Rebatch Your Soap

If your soap has been curing for several weeks and is still showing prominent soda ash or failing a zap test, consider rebatching.

To rebatch, grate or chop up soap scraps and place them in a crockpot or double boiler with a bit of water or milk. Heat slowly until the soap melts, then pour into molds. This resets the saponification process.

Plane or Sand Bars

If you have a batch with minor soda ash and don’t want to rebatch entirely, you can simply plane or sand away the ash using a vegetable peeler, cheese grater, fine sandpaper, or belt sander. Smooth away the powder and residue for fresh bars.

Rewrap and Let Cure Longer

Before resorting to rebatching or altering bars, you can also try letting them cure longer first. If a zap test shows they are safe but still have soda ash, rewrap bars in butcher paper or wax paper and allow them to cure for 4-6 weeks. The extra time may allow the ash to dissipate.

The key is patience and testing before determining your soap isn’t salvageable. In many cases, the soda ash will fade or disappear with extra cure time without any extra work on your part.

Perfecting Your Recipe and Technique

While environmental factors definitely contribute to soda ash, the recipe and method you use can also play a role. Don’t just blame humidity! Tweaking your superfatting, ingredients, and technique can help create the perfect bar and prevent soda ash batch after batch.

Tweak Your Superfat Percentage

The superfat in your recipe impacts how quickly your bars harden and become less alkaline. A higher superfat, like 8–15%,, will speed saponification versus a lower 5% superfat. Start by upping your superfat if you notice persistent soda ash batch after batch.

Pay Attention to Ingredients

Some oil and additive combinations encourage soda ash growth. Batches with a high percentage of soft oils like olive oil seem more susceptible. Swapping out half the olive oil for harder palm oil can help. Avoid adding sugar, which provides food for ash.

Stick Blend Correctly

Your mixing method plays a key role! Blending too little can lead to separation and ash-attracting spots from excess oils. But blending too much accelerates trace, prompting the soap batter to heat up quickly and encouraging soda ash-producing conditions.

Aim for bringing your soap to a light trace with an emulsion-like texture. Use brief 5–10 second bursts, allowing the batter to rest in between for an ideal trace and temperature.

Getting your recipe, additives, and mixing technique dialed in makes a big difference in battling soda ash. Don’t just address environmental factors; examine your methods too for the best results!

While soda ash may seem like an inevitable soapmaking woe, a few easy tricks can help you win the battle. By controlling your environment, tweaking your recipe, properly preparing your lye solution, and testing your batches, you can transform from soda ash victim to homemade cold process soap pro. With your newfound knowledge, go forth and froth up fabulous, frosty-free soap!

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