Goat Milk Soap Recipe: Cold Process Bars

This cold-process goat milk soap combines olive, coconut, shea butter, and castor oils with goat milk and sodium hydroxide to make six firm, creamy bars. The milk is frozen before mixing to help limit scorching, and the finished bars cure for six weeks before use.

Ingredients

8.8 oz (250 g) olive oil
4.4 oz (125 g) coconut oil, solid
2.65 oz (75 g) shea butter
1.76 oz (50 g) castor oil
5.3 oz (150 g) plain goat milk, frozen in cubes or a shallow slab for at least 8 hours
2.43 oz (69 g) sodium hydroxide (100% lye; not drain cleaner with additives)

Instructions

Prepare the workspace and equipment. Before weighing anything, protect the counter and put on splash goggles, nitrile gloves, long sleeves, and closed shoes. Keep children and pets out, open a window or use good ventilation, and set out a digital scale, stainless-steel or lye-safe plastic containers, an immersion blender, a spatula, and a silicone or lined soap mold that holds about 700 ml. Do not use aluminum: lye reacts with it. Keep vinegar away from the work area; it is not a substitute for proper lye handling or cleanup.
Freeze the goat milk. Freeze the measured 150 g (5.3 oz) goat milk in a shallow container or ice-cube tray for at least 8 hours. When ready to make soap, put the frozen pieces in a lye-safe container set in a cool-water bath. The bath helps manage heat but must not get into the milk. Measure all ingredients by weight, not by volume.
Make the lye-milk mixture. Slowly sprinkle the 69 g (2.43 oz) sodium hydroxide over the frozen milk a little at a time, stirring carefully between additions with a stainless-steel spoon. Do not pour milk onto a pile of lye, and do not lean over the container. The mixture will warm and the milk may turn cream-colored or tan; that is common. Pause if it gets hot, let the cubes melt gradually, and continue stirring until no lye crystals remain. Keep the mixture below 90°F (32°C) if possible. Never use it while crystals are visible.
Melt and combine the oils. Weigh the coconut oil and shea butter into a heat-safe stainless-steel pot or container and warm gently until just melted. Stir in the olive and castor oils, then let the blend cool. Aim for both the oils and lye-milk mixture to be about 80–90°F (27–32°C). If one is warmer, let it stand; do not rush the process by adding ice or water to either mixture.
Blend to light trace. Pour the lye-milk mixture into the oils carefully. Use the immersion blender in short pulses, alternating with hand-stirring, and keep the blender head submerged to avoid splashing. Stop when the batter is evenly mixed and leaves a faint trail on its surface that briefly remains before sinking back in. This is light trace; blending until very thick can make the soap difficult to pour.
Pour and leave the mold undisturbed. Scrape the batter into the mold and tap it gently on the counter to release large air pockets. Cover loosely with a lid or cardboard, but do not wrap it in towels or place it near a heater; goat milk soap can overheat. Leave it in a cool, draft-free place for 24–48 hours. The loaf should feel firm enough to unmold. If it is still soft, give it more time rather than forcing it.
Unmold, cut, and cure. Wearing gloves, remove the loaf and cut it into six bars, each roughly 1 inch (2.5 cm) thick. Set the bars on a rack with space between them in a cool, dry, ventilated place, away from direct sunlight. Turn them occasionally and cure for six weeks. The bars will lose water and become firmer during this period. Do not use them early just because they feel solid.

Tips

Use a reliable scale and keep the oil blend unchanged. Lye amounts depend on the exact oils and their weights. Do not swap one oil for another by equal weight or adjust the lye by guesswork. If changing the recipe, enter every oil into a reputable soap calculator and verify the sodium hydroxide amount before making it.
Keep the milk cool without rushing. Gradual lye additions to frozen milk help limit darkening, but some cream or tan color is normal. If you want a pale bar, keep the ingredients cool and avoid insulating the mold; color can still vary with the milk and the temperature reached during mixing.
Do not use kitchen tools for food afterward. Set aside containers, spoons, and molds for soapmaking. If fresh batter or lye solution spills, keep people and pets away, wear protective gear, and follow the sodium hydroxide supplier’s safety guidance for cleanup. Do not handle uncured batter with bare hands.
Give the bars air while curing. A rack or ventilated shelf works better than a closed box. Bars touching one another or sitting on a damp surface can cure unevenly. If your home is humid, choose the driest well-ventilated location available and leave extra space between bars.

Serving Suggestions

Soap is not food, so these bars are for washing only. After the full six-week cure, keep one by a handwashing sink or use it in the shower with a draining soap dish. A dish that lets water run away helps the bar dry between uses and last longer. If the bar feels soft or leaves a slippery coating on the dish, allow it to dry fully before using it again; do not leave it sitting in a puddle.

For a first use, wet the bar and hands, work up a lather, and rinse the skin and the bar thoroughly. Store a spare bar in a dry spot rather than leaving the whole batch beside a frequently splashed sink. This recipe makes six modest bars, so one can be kept for regular use while the others remain on the curing rack or are wrapped after curing.

Variations

Fragrance: This base recipe is unscented. If you want fragrance, use a skin-safe soap fragrance or essential oil that is suitable for cold-process soap, and follow the supplier’s maximum usage rate for rinse-off products. Weigh it accurately and stir it in by hand at light trace. Fragrances can accelerate thickening or change the final color, so check the supplier’s notes and avoid adding an unmeasured splash.

Milk powder: If handling frozen milk is inconvenient, use a soapmaking calculator and a tested milk-powder method rather than replacing the liquid amount at random. Goat milk powder can be dispersed into oils or reconstituted according to its supplier, but the amount and method affect the batter. Keep the total liquid and lye calculation consistent with the revised formula.

Simple color: Leave the soap natural for a cream-to-tan finish, or use a small amount of a colorant specifically made for cold-process soap. Some botanicals turn brown or speckle over time, and water-based food coloring may not behave as expected. Test unfamiliar colorants in a small batch and never add extra liquid without recalculating the recipe.

Different mold size: A loaf mold can be replaced with individual silicone cavities, but the bars may set at different rates and be ready to unmold sooner. Check them after 24 hours and handle them with gloves until fully cured. The number of bars depends on cavity size, while the six-week cure still applies.

Storage and Reheating

There is no reheating step for cold-process soap. Once cured, store unused bars in a cool, dry place with airflow, away from direct sunlight, heat, humidity, and splashes. A paper wrapper or breathable box is suitable after the bars have completed their cure; avoid airtight wrapping if a bar is still losing moisture. Label the batch with its making date so the cure period is easy to track.

Well-stored bars are generally best used within about a year. Natural oils can eventually develop an off smell or orange spots, particularly if the soap is kept warm or damp. Discard a bar if it has an unusual rancid odor, visible contamination, or a texture that seems deteriorated. Keep uncured soap batter and all lye supplies secured away from children, pets, food, and household utensils.

Frequently Asked Questions

Why freeze the goat milk before adding lye?

Dissolving sodium hydroxide releases heat. Starting with frozen milk slows the temperature rise and helps reduce the chance of scorching, which can darken the milk and give the soap a stronger cooked-milk smell. The milk may still change color, and that alone does not mean the batch has failed. Add the lye gradually and wait for each addition to dissolve.

Can I use liquid goat milk straight from the carton?

Not with this method as written. The recipe’s milk is frozen first to help control heat when the lye is added. Using room-temperature milk can cause much faster heating and scorching. If you prefer another approach, use a reputable, tested goat milk soap method and follow its exact liquid and lye instructions rather than making an improvised substitution.

How do I know the soap is ready to unmold?

Check after 24 hours, then wait up to 48 hours if needed. The loaf should be firm enough to release from the mold without smearing or denting deeply under gentle pressure. Temperature, mold material, and the oils can affect setting time. Unmolding is not the same as curing: cut bars still need the full six weeks of drying time.

Can I reduce the six-week cure?

No. A bar can become firm before it has finished curing. The waiting period allows water to evaporate and gives the soap time to become harder and last longer in use. Keep the bars spaced apart in a ventilated area for the full six weeks; do not shorten the cure by baking or placing them on a heater.

What if I want to change the oils or make a larger batch?

Recalculate the sodium hydroxide for the new oil types and weights with a soap calculator before mixing. Different oils require different amounts of lye, and scaling only the oils without recalculating can leave a batch caustic or fail to make proper soap. Use a digital scale, retain the same superfat target when calculating, and wear the same protective gear for every batch.

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