Safety First — Working with Lye

Essential PPE (Personal Protective Equipment)

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  Safety goggles — Full-seal chemical splash goggles, not regular glasses. Lye splashes can cause permanent eye damage.
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  Chemical-resistant gloves — Nitrile or rubber gloves. Latex is acceptable but nitrile is preferred for chemical resistance.
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  Long sleeves and closed-toe shoes — Cover exposed skin. A long-sleeved shirt and pants protect against splashes.
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  Apron — Recommended to protect clothing and provide an extra layer between you and splashes.

The Golden Rules

• 1ALWAYS add lye TO water — never water to lye. Adding water to lye can cause a violent exothermic reaction that may splatter caustic solution. Remember: "Snow falls on the lake."
• 2Never use aluminum containers or utensils. Lye reacts with aluminum, producing toxic hydrogen gas. Use stainless steel, heat-resistant plastic (HDPE/PP), or silicone.
• 3Work in a ventilated area. When lye dissolves in water, it releases caustic fumes. Open a window, use a range hood, or work outdoors.
• 4Keep children and pets out of the workspace while mixing lye and during the entire soaping process.
• 5Have running water nearby. In case of skin contact, you need immediate access to cool running water.
• 6Never leave lye solution unattended. A clear lye solution looks like water and is extremely dangerous if someone were to touch or drink it.

If Something Goes Wrong

Storage & Disposal

• Store lye in airtight, clearly labeled containers away from moisture. Lye is hygroscopic and absorbs water from the air.
• Label containers clearly: "DANGER — Sodium Hydroxide" or "DANGER — Potassium Hydroxide."
• Store in a cool, dry place out of reach of children and pets.
• Never pour large quantities of concentrated lye solution down the drain. Dilute heavily first.
• Check your local regulations for chemical disposal requirements.

Lye Calculator Safety

• Always double-check your lye calculations before measuring. Even small errors can result in a lye-heavy bar that irritates skin.
• Never skip the superfat — it's your safety buffer. A superfat of 5% means 5% of the oils remain unsaponified, ensuring no free lye remains in your soap.
• Start with small batch sizes (500g or less) when learning. Small batches are easier to manage and less wasteful if something goes wrong.
• Use a reliable digital scale accurate to 0.1g for measuring lye. Volume measurements are not precise enough.
• When in doubt, run your recipe through two different lye calculators to verify results.