1 hour and 30 minutes
0 serving
Medium
0 kcal
Ingredients
- 3 quarts strained used cooking oil
- 1.1 lb 96-99% lye (sodium hydroxide)
- 2 quarts ice-cold water (for lye solution)
- 2 quarts 70%+ grain alcohol or ethanol
- 1 cup granulated sugar
- 2 cups boiling water (for sugar syrup)
Directions
- <strong>Make the Glycerin Syrup (Sugar Solution):</strong> Stir sugar into boiling water until fully dissolved; set aside. This syrup boosts clarity and glycerin content.
- <strong>Mix the Lye (SAFETY FIRST):</strong> In a heavy plastic or stainless bucket, add cold water. Wearing gloves, goggles and a mask, slowly sprinkle in lye while stirring with a long wooden spoon. Work outdoors or under a vent; fumes are strong. Let cool until lukewarm.
- <strong>Combine Oil & Alcohol:</strong> In a second large bucket whisk together used oil and alcohol for 2–3 minutes.
- <strong>Saponify:</strong> Slowly pour the warm lye solution into the oil/alcohol mix, stirring non-stop. The blend will thicken and change color; keep going for an even reaction.
- <strong>Trace Stage:</strong> Stir until the soap reaches “trace”—when drizzled batter leaves a visible ribbon on the surface. This can take 30–60 min. If it separates, just keep stirring; it will come back together.
- <strong>Add Glycerin Syrup:</strong> Pour in reserved sugar solution; stir well. The soap may loosen again—this is normal.
- <strong>Mold & Bubble Pop:</strong> Pour into plastic molds (milk cartons, margarine tubs, or silicone soap shapes). Lightly spritz the top with 70% alcohol to pop bubbles for a smooth finish.
- <strong>Cure:</strong> Let soap sit 24–48 h in a cool, airy spot. Unmold, cut into bars and cure 2–3 weeks before use so lye fully neutralizes and bars harden.
Chef’s Tips
- <strong>Safety First:</strong> Always wear PPE—rubber gloves, goggles, mask—and keep kids/pets away. Work in a ventilated area.
- <strong>pH Check:</strong> After curing, test pH with strips; safe soap reads 8–9.
- <strong>Customize:</strong> Stir in skin-safe fragrance or color at trace for scented or colorful bars.
- <strong>Storage:</strong> Store cured bars in a dry, airy place. A light “sweat” from glycerin is normal and harmless.
- <strong>Tweaks:</strong> For harder bars add a spoon of stearic acid; for extra bubbles blend in a squirt of neutral dish soap at trace.
From Ancient Clay to Crystal Bars: The Story of Glycerin Soap
DIY glycerin soap looks modern with its see-through sparkle, but the chemistry behind it began on Babylonian tablets around 2800 BCE. Those early cleaners mixed animal fat with wood ash—the first saponification hack. Fast-forward to 1779 when Swedish chemist Carl Wilhelm Scheele isolated glycerin, the moisturizing by-product that gives today’s homemade bars their skin-loving reputation.
Why Keep the Glycerin?
Industrial plants often strip glycerin to sell to pharmaceutical and explosives markets. Artisan soap keeps it in, so the final bar naturally pulls moisture from the air to your skin, leaving dishes, laundry, and even your face clean without that tight, dry feel.
Green Perks of Recycling Fryer Oil
Every quart of used cooking oil you turn into soap is a quart that won’t clog pipes or pollute waterways. Add a biodegradable sugar syrup for clarity and you’ve got a zero-waste powerhouse that cuts grease, lifts stains, and lathers like a dream.
Ready to Start?
Gather your strained oil, lye, and a long wooden spoon. Slip on those gloves, set a timer for 90 minutes, and let chemistry do the heavy lifting. Two dozen crystal-clear bars later, you’ll never see “waste” oil the same way again.