Have you ever made a beautiful swirled soap only to come back to it the next day and the surface is covered with an ashy substance?
This is ash. Soda ash (commonly referred to as ash) is a pesky little problem that just about every soapmaker has encountered at one time or another. What is it? Ash is sodium carbonate. Sodium carbonate forms where un-reacted lye meets air during the time that you pour your soap until when it is saponfied 24-48 hours later. We know it is sodium carbonate if it is soluble in water (you can rinse it off) and it covers the surface of the soap that is exposed to air. If you have white dots or streaks in your soap, especially below the surface, you might have lye spots, stearic spots or something else.
If you cut your soap to soon and it hasn’t fully saponfied, you can get ash that covers the entire bar of soap, as the last tiny bit of un-reacted lye reacts to the air!
The good news about ash is two-fold. Ash is an aesthetic issue; it does not affect the effectiveness of your soap and ash is preventable.
If you do get ash, no biggy, your soap might not look as pretty and colorful below the blanket of white, but it will still clean you. To remove the ash, you can steam it, rinse it under warm water or even plane it off.
How to Prevent Ash on Soap
To prevent ash, spray your soap with alcohol. Find the highest grade of alcohol that you can find. We can get 91% Isopropyl Alcohol here. Put it into a fine mist spray bottle.
I spray my soap twice, once right after pouring and then again about 30 minutes later. That usually does the trick and prevents ash from forming.