Special soaps: salt, beer and milk soaps - recipes and guide
TL;DR: Salt soaps harden quickly (2-5 minutes after adding salt) and are extremely hard. Beer soap requires alcohol skimming and freezing. Dairy soaps (goat, coconut, oatmeal) need freezing or adding to the trace to preserve the active ingredients. Each type has specific techniques, but production is easy.
In addition to the standard cold process recipes, there is a group of soaps that require a slightly different approach. Salt soaps solidify so quickly that you need to have the mold precisely prepared. Beer soap requires defoaming and cooling the alcohol. Milk soaps need freezing to preserve color and fragrance.
Each of these types has its own logic - if you understand it, production is easy.
Salt Bars — the hardest and simplest variant
Salt soaps contain 80-100% sea salt by weight of oils and solidify in minutes. The result is a hard, exfoliating bar with a thick lather that lasts an exceptionally long time.
Salt soaps are one of the simplest and hardest options. They contain large amounts of sea or Himalayan salt - 80-100% by weight of oils - added to the trace. The result is a hard, densely foaming bar with a gently exfoliating surface that lasts an exceptionally long time.
Why salt in soap?
Sodium chloride (NaCl) in soap does not alter saponification but dramatically affects physical properties:
Hardness: Salt causes rapid crystallization of soap molecules. Salt soaps are as hard as stone when removed from the mould (in 12-18 hours).
Lather: Salt soaps lather surprisingly well - a thick, silky lather. Paradoxically, although salt usually breaks down lather in water, the effect is the opposite with high superfat (20%) soaps.
Exfoliation: Fine salt crystals on the surface exfoliate the skin. Coarser salt = stronger exfoliation.
Key rule: salt is added ONLY ON TRACE
Salt accelerates solidification so dramatically that soap solidifies within 2-5 minutes after adding salt. The mould must be prepared, the ingredients and essential oils added, everything mixed - only then do you add the salt, stir quickly and pour immediately.
Recipe: Coconut salt soap
| Yield | ~1,100 g |
|---|---|
| Difficulty | ★★★☆☆ (due to fast pouring speed) |
| Curing | 4–6 weeks |
Ingredients:
- 490 g coconut oil (70%)
- 140 g olive oil (20%)
- 70 g castor oil (10%)
- 92,0 g NaOH
- 265 g of water
- 490 g fine sea salt (70 % by weight of oils)
- Super fat: 20% (necessary - without high SF, salt soap would be drying)
- Optional: 14 g essential oil (peppermint, lavender)
NaOH calculation: Coconut (490×0.178=87.2) + olive (140×0.134=18.8) + ricin (70×0.128=9.0) = 115.0 g for 0% SF × 0.80 = 92.0 g. (Exact calculation in the calculator recommended.)
Procedure:
- Prepare the mould, weigh out the salt, have everything ready BEFOREhand.
- Standard CP procedure - oil + lye → trace.
- On the trace add EO, paint, mix quickly.
- Add salt, stir for 5-10 seconds.
- Immediately pour into the mould. The soap may begin to solidify in the container.
- Remove from the mold after 12-18 hours - earlier than the usual CP soap.
- Slice immediately - in 24 hours it will be too hard to cut.
Tip: Salt soaps are usually made in individual silicone moulds instead of a loaf - eliminating the problem of slicing.
Beer soap — gentle and conditioning
The beer contributes polyphenols and vitamins from hops and yeast that enhance conditioning. The alcohol in the beer must be evaporated (24-48 hours of aeration or heating) before adding to the liquor, and the beer must be frozen to prevent overheating.
Beer in soap is not just a marketing gimmick. Hops and yeast residues in beer (especially unpasteurized beer) add specific compounds to soap - polyphenols, B vitamins and amino acids. The result is a mild, conditioning soap with a typically golden color.
How to work with beer in soap
Beer contains alcohol and CO₂ - both of which complicate production:
Alcohol reacts with the lye and causes rapid overheating. Therefore, the beer is foamed and heated to evaporate the alcohol before use.
Sugars in beer react with lye and caramelize - causing the soap to darken. The darker the beer, the darker the soap. A light lager will give a golden soap, a dark porter will give a brownish-black soap.
Preparation of beer before production
- Open the beer 24-48 hours in advance and let it stand freely (the CO₂ will evaporate and much of the alcohol will evaporate).
- Alternatively: heat the beer to 70-80 °C for 15-20 minutes (evaporate the alcohol), then cool.
- Before use: freeze the beer into ice cubes (like milk) to reduce the risk of overheating when adding the lye.
Recipe: Basic beer soap
Ingredients:
- 245 g coconut oil (35%)
- 245 g olive oil (35%)
- 140 g sunflower oil (20%)
- 70 g castor oil (10%)
- 99,0 g NaOH
- 130 g frozen beer (foamed)
- 130 g distilled water
Procedure: Prepare the lye solution from a combination of frozen beer and water. Add NaOH slowly, controlling the temperature below 30 °C. Following standard CP procedure.
Result: A golden to caramel soap with mild conditioning properties. The smell of beer is not noticeable in the finished soap.
Milk soaps — varieties for different skin types
Dairy soaps (goat, cow, coconut, oat) all contain lactose and proteins that increase conditioning. Each type of milk has specific properties - goat's is the most common, coconut adds extra fat, and oatmeal is gentle for sensitive skin.
Dairy soaps make up an entire category - goat, cow, oat, rice, coconut milk. They all work on a similar principle: lactose and milk proteins contribute to conditioning properties, lactic acid promotes gentle exfoliation.
For kozí mléko - the most popular option - see separate detailed guide:
→ Goat milk soap — complete guide and recipe
Brief overview of other dairy variants
Coconut milk: The high fat content (17-24%) adds extra conditioning. The soap is creamy white. Technique: same as goat's milk (freeze or add to trace).
Oat milk: Gentle, for sensitive skin. Low in fat, but beta-glucans from oats contribute to conditioning. Colour of the resulting soap: beige.
Rice milk: Popular in Asian cosmetics. Contains inositol and amino acids. Light colour of the resulting soap.
Tallow soaps
Tallow soap is experiencing a renaissance thanks to the ancestral/carnivore community and the interest in biocompatible cosmetics. The composition of bovine tallow (palmitic + stearic + oleic acid) is strikingly similar to human sebum.
See separate page for detailed guide, tallow rendering technique and recipes:
→ Tallow soap — complete guide
Frequently asked questions
Why does salt soap harden so quickly after adding salt? Sodium chloride (NaCl) causes soap molecules to crystallize - a physical process, not a chemical one. As a result, the resulting soap is extremely hard and lasts the longest in the bathroom of all household soaps.
How do I know if the salt in salt soap is too coarse? Coarser salt (coarse grain sea salt) exfoliates more intensively - suitable for feet and body. Fine salt is better suited for the face. If the salt in the soap is uncomfortable, use a finer type next time.
Can I add sea salt to a normal recipe without adjusting the oils? Salt accelerates solidification, so it won't work in a normal recipe. The soap would become very hard and brittle. Salt soaps require a special formulation with a higher SF (20%) along with recipe designed ingredients.
The smell of beer disappears in the finished soap? Yes - the alcohol and volatile compounds in the beer evaporate during maturation. The aroma of the beer is only noticeable when it is first brewed. The conditioning benefits remain.
Which lotions are best for soap? Goat's milk is most popular because of its lactic acid and fine fat. Coconut milk adds extra conditioning. Oat milk is gentle for sensitive skin. All work - choose according to your goal.
Can I combine salt and milk in one recipe? Technically yes, but it's not recommended - both ingredients accelerate solidification and the combination would be too fast. Better to choose one type of specialty soap per batch.
See also:
- Recipes for beginners — if you haven't made your first batch yet
- Soap additives - honey, silk, clays and other special ingredients
- Natural colorants - how to dye soap naturally
⚠️ Recipe disclaimer
This recipe was created or revised with the help of artificial intelligence tools and has undergone NaOH gram recalculation. Nevertheless, we recommend verifying lye amounts in an independent calculator (e.g. SoapCalc or Brambleberry). Working with sodium hydroxide requires protective equipment — see Lye safety. Information is for educational purposes; the manufacturer is not liable for damages resulting from their use.
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