Fluid Hot Process Soap

Fluid hot process soap combines the speed advantages of hot process soap with the aesthetic appeal of cold process soap. By carefully controlling temperature and using a blend of oils that create a naturally fluid batter, you achieve a soap that remains pourable and elegant. This intermediate technique is perfect for soap makers who want beautiful designs without the long curing time.

Ingredients

Oils & Butters

• 18.0 oz (510g) coconut oil
• 12.0 oz (340g) canola oil
• 12.0 oz (340g) olive oil
• 8.0 oz (227g) castor oil

Lye Solution

• 5.4 oz (153g) sodium hydroxide
• 13.0 oz (369g) distilled water

Additives (Optional)

• 0.6 oz (17g) fragrance oil or essential oil blend
• Colorants (oxide or mica, 0.5-1 tsp)
• Exfoliants (ground oatmeal, poppy seeds, or pumice, 2-3 tbsp)

Equipment Needed

• Stainless steel pot (2-3 qt capacity)
• Digital scale
• Large glass or stainless steel mixing bowl
• Stick blender
• Stainless steel spoon
• Thermometer (digital preferred)
• Safety goggles and gloves
• Heat source (stove or hot plate)
• Towels for insulation
• Silicone soap molds or parchment-lined containers
• Long-handled whisk or paddle

Instructions

Step 1: Prepare Safety Equipment

Before beginning, review lye safety procedures and ensure you have adequate ventilation. Put on safety goggles, gloves, and long sleeves. Have baking soda and vinegar within arm's reach for emergency cleanup. Position your work area to allow easy access to all materials without reaching over containers.

Step 2: Measure Oils Precisely

Using your digital scale, measure each oil into a stainless steel pot. The combination of oils with varying viscosities helps maintain fluidity throughout the process. Start with higher percentages of liquid oils like canola and olive oil, which keep the batter in motion longer during hot process.

Step 3: Heat Oils to Temperature

Place the pot of oils on a stove set to medium heat or use a hot plate. Using your thermometer, gradually bring the oil mixture to 170-180°F. This higher initial temperature is necessary for fluid hot process because it helps the soap stay liquid as it goes through saponification. Stir occasionally to ensure even heating.

Step 4: Prepare Lye Solution

Measure distilled water into a glass container. Slowly add sodium hydroxide to the water in small amounts, stirring gently between additions. Never add water to lye. The solution will become very hot (up to 200°F). Let it cool to approximately 165-175°F. This typically takes 15-25 minutes. The solution should be clear.

Step 5: Combine Lye and Oils

With both lye solution and oils at 165-175°F, slowly pour the lye into the oils while stirring constantly with a stainless steel spoon. Continue stirring for 5-8 minutes until the mixture reaches a light trace—it should look similar to thin pudding and coat the back of a spoon.

Step 6: Begin Heat Phase

Once you reach light trace, carefully place the entire pot into a larger pot filled with hot water (water bath/double boiler method) or keep it on low heat. Maintain the mixture at 160-170°F while cooking. Stir frequently (every 5-10 minutes) using a stick blender in short pulses or a paddle. The soap will go through several phases.

Step 7: Monitor Phase Changes

The soap will progress from grainy-looking to creamy to translucent. Around 30-45 minutes into cooking, it may separate or look oily, then come back together. This is normal. Around 60 minutes, the soap should look smooth, glossy, and pourable. At this point, run a zap test: dip your clean finger in the soap, touch it to your tongue, and it should feel soapy but not burny. If you feel electricity/stinging, cook longer.

Step 8: Achieve Proper Fluidity

The key to fluid hot process is catching the soap at exactly the right moment—when it's fully saponified but still pourable. This typically occurs 45-90 minutes into cooking. You should be able to pour a small amount smoothly. If it becomes too thick, add small amounts (1 tbsp at a time) of distilled water to adjust consistency. If it becomes too thin, cook longer to remove water content.

Step 9: Add Color and Fragrance

Remove from heat and let cool for 5 minutes. Add colorants (if using) and mix thoroughly with a spoon or stick blender for 1-2 minutes until evenly distributed. Add fragrance oil or essential oil and stir well for 2-3 minutes. Add any exfoliants or botanical matter and fold in gently.

Step 10: Pour Into Molds

Working quickly while the soap is still warm and pourable, transfer it into molds. You can tilt molds for ombré effects, layer different colors, or create swirls with a spatula. The soap will set as it cools. Once poured, let it cool uncovered for 2-4 hours at room temperature.

Step 11: Remove from Molds and Cut

After cooling, remove soap from molds. If the bar is firm, you can cut it into smaller pieces if desired. Fluid hot process soap can be used immediately, though a 24-48 hour cure period results in harder bars and better lather.

Step 12: Storage

Store finished bars in a cool, dry location away from direct sunlight. Use a breathable soap dish to prolong bar life.

Tips for Success

• Temperature Precision: Fluid hot process depends on maintaining steady temperatures. Invest in a reliable thermometer and check it frequently.
• Blend with Stick Blender: Using a stick blender in short pulses helps distribute heat evenly and keeps the soap moving, maintaining fluidity.
• Don't Overmix: Excessive blending can cause the soap to overheat or become too thick. Use brief pulses between visual checks.
• Water Content: If your soap becomes too thick before reaching the desired fluidity, resist adding water. Instead, cook longer to evaporate excess moisture and maintain true saponification.
• Keep Notes: Document cooking times, final temperatures, and consistency markers. This helps you perfect the technique for future batches.

Variations

• Layered Design: Divide the soap at medium fluidity, color different portions, and pour them in alternating layers in the mold.
• Swirled Effect: Pour soap into the mold, then use a chopstick or skewer to create figure-eight swirls through the layers.
• Embedded Objects: Place soap-safe items (seeds, herbs, small stones) in the mold before pouring for embedded designs.

Cost Breakdown

Estimated Cost per Bar: $0.84-$0.94

Related Recipes

• Hot Process Crockpot Soap
• Marbled Clay Hot Process Soap
• Turmeric Layered Soap

Common Issues & Solutions: If soap becomes too thick, don't panic—it's still safe to use. Rebatch the soap by cutting it into small cubes and reheating gently with a small amount of water to achieve desired consistency. If soap is too thin, continue cooking longer to reach proper saponification and water evaporation.