If you've ever wondered why your handmade soap feels different from a store-bought bar, or why pH matters in soap making, you're in the right place. Understanding pH is one of those game-changing fundamentals that separates good soap from great soap.
What is pH and Why Does It Matter in Soap Making?
pH measures how acidic or alkaline a substance is, on a scale of 0–14. Neutral is 7, anything below is acidic, and anything above is alkaline. True soap sits on the alkaline side, typically between pH 8–10, and that's completely normal and safe for skin.
What's the Ideal pH for Handmade Soap?
Most well-made cold process or hot process soaps fall between pH 8 and 10. Anything above 11 can be harsh on skin and may indicate your soap hasn't fully saponified. A pH below 7 means it's not actually soap, it's a synthetic detergent bar.
How to Test the pH of Your Soap
There are three common methods:
- pH strips, quick, affordable, and good enough for most makers
- Digital pH meter, more accurate but requires calibration
- The zap test, touch the soap to your tongue; a "zap" or tingle means lye is still active (not recommended!)
What Affects pH in Handmade Soap?
- The type and amount of lye used (NaOH for bar soap, KOH for liquid soap)
- Your water discount
- Cure time, pH naturally drops as soap cures over 4–6 weeks
- Superfat percentage
Common pH Problems and How to Fix Them
- pH above 11: Soap may be lye-heavy, extend cure time and retest
- Uneven pH across the bar: Incomplete mixing or partial gel phase
The Bottom Line
Don't stress too much about chasing a perfect pH number. A well-formulated recipe, accurate measurements, and proper cure time will naturally result in a skin-safe bar. Test regularly, trust your process, and keep making!
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