Fat Selection

Part of Soap Making

The fat or oil you choose determines everything about your finished soap — its hardness, lather, cleaning power, shelf life, and skin feel. Understanding fat chemistry lets you formulate soap from whatever resources your environment provides.

Why Fat Choice Matters

Soap is the product of a chemical reaction between a fat and a strong alkali. Different fats contain different fatty acids, and each fatty acid contributes specific properties to the finished soap. There is no single “best” fat — the ideal soap blends multiple fats to balance hardness, lather, and mildness.

In a survival scenario, you use what you have. But understanding what each fat contributes lets you predict results and improve your product over time.

Fatty Acid Basics

Every fat is composed of glycerol bonded to three fatty acid chains. The type and proportion of these fatty acids determine the soap’s properties.

Key Fatty Acids and Their Effects

Fatty Acid	Found In	Soap Property	Effect
Lauric acid	Coconut oil, palm kernel	Hardness, big bubbles	Highly cleansing, can be drying
Myristic acid	Coconut oil, butter	Fluffy lather	Cleansing, somewhat drying
Palmitic acid	Tallow, palm, lard	Hardness, stable lather	Long-lasting bar
Stearic acid	Tallow, cocoa butter	Hardness, waxy feel	Very hard, stable bar
Oleic acid	Olive oil, lard, tallow	Conditioning, moisturizing	Mild, low lather
Linoleic acid	Sunflower, safflower	Skin conditioning	Soft bar, shorter shelf life
Ricinoleic acid	Castor oil	Lather boost, moisturizing	Unique creamy lather

A balanced soap recipe targets roughly 40-50% hard/cleansing fatty acids (lauric, myristic, palmitic, stearic) and 50-60% conditioning fatty acids (oleic, linoleic). This produces a hard bar that lathers well without over-drying skin.

Animal Fats

Animal fats are the most historically common soap-making fats. They are a byproduct of butchering and cooking — free resources in any community that raises livestock.

Tallow (Beef Fat)

The gold standard for traditional soap. Beef tallow produces a hard, white, long-lasting bar with stable lather.

Properties:

• High in palmitic and stearic acids — excellent hardness
• Moderate oleic acid — some conditioning
• Produces a firm bar that cures well
• Nearly odorless when properly rendered

Rendering tallow:

1. Cut all fat and suet from the carcass, removing any meat or blood
2. Chop or grind into small pieces (the smaller, the faster it renders)
3. Place in a heavy pot with 1 cup of water per kilogram of fat
4. Heat on low — the fat should melt slowly, never fry or smoke
5. Strain through cloth when all solid pieces have liquefied
6. Allow to cool and solidify — scrape off any brown sediment (cracklings) from the bottom
7. Re-melt and strain again for cleaner tallow
8. Repeat until the tallow is white and odorless

Lard (Pig Fat)

Softer than tallow, lard produces a slightly softer bar with better lather and more conditioning.

Properties:

• Higher in oleic acid than tallow — more moisturizing
• Lower melting point — bars are slightly softer
• Excellent lather quality
• Widely available in any pig-raising community

Rendering: Same process as tallow. Leaf lard (from around the kidneys) is the highest quality.

Other Animal Fats

Fat	Source	Soap Quality	Notes
Goat tallow	Goats	Good, similar to beef	Slightly softer than beef tallow
Sheep tallow	Sheep	Hard, waxy	Contains lanolin — conditioning
Poultry fat	Chicken, duck, goose	Soft, short shelf life	Best blended with harder fats
Bear fat	Hunting	Soft, rich	Historically prized; seasonal
Fish oil	Fishing	Very soft, strong odor	Makes liquid or soft soap only

Fish oil soap has an extremely strong and persistent odor. Use only as a cleaning soap for tools and equipment, never for personal hygiene unless you have no other fat source.

Plant Oils

Plant-based fats expand your options, especially in climates where livestock are scarce.

Olive Oil

Produces “Castile soap” — mild, gentle, and highly conditioning. Pure olive oil soap is soft, does not lather profusely, and requires a long cure time (6-12 months for best results), but it is one of the finest soaps for skin care.

Sourcing: Press ripe olives in a screw press or stone mill. Mediterranean climates, or anywhere olive trees grow.

Coconut Oil

The opposite of olive oil — coconut oil soap is extremely hard, lathers profusely even in salt water, and cleans aggressively. Used alone, it is drying to skin. Blend at 15-30% of a recipe for balanced results.

Sourcing: Crack coconuts, grate the meat, soak in hot water, and skim the oil that rises to the surface. Or press dried copra (coconut meat).

Sunflower Oil

A conditioning oil high in linoleic acid. Produces soft bars with good skin feel but poor shelf life (tends to go rancid). Best used at 10-20% of a recipe as a conditioning additive.

Sourcing: Harvest mature sunflower heads when seeds are plump and dark. Dry, shell, and press the seeds.

Other Plant Oils

Oil	Source	Soap Properties	Climate
Palm oil	Palm fruit	Hard, stable, moderate lather	Tropical
Sesame oil	Sesame seeds	Conditioning, moderate hardness	Warm temperate
Rapeseed/canola	Rapeseed	Conditioning, soft bar	Temperate
Walnut oil	Walnuts	Very conditioning, soft	Temperate
Hemp seed oil	Hemp plants	Conditioning, green-tinted	Temperate
Shea butter	Shea nuts	Hard, very moisturizing	Tropical Africa

Rendering and Preparation

Regardless of fat source, proper preparation is essential for quality soap.

Fat Quality Requirements

• Clean — no meat, blood, bone, or skin contamination
• Fresh or properly stored — rancid fat produces rancid soap (though it still cleans)
• Rendered (for animal fats) — raw fat contains connective tissue and water that interfere with saponification
• Filtered — strain through cloth to remove particles

Signs of Rancid Fat

Rancid fat contains free fatty acids from decomposition. Mildly rancid fat still makes usable soap, but the product will smell off.

• Yellowish color (in fats that should be white)
• Sour or “old grease” smell
• Sticky texture
• Visible mold — discard, do not use

Slightly rancid fat can be cleaned by boiling with water (1:1 ratio), adding a tablespoon of salt, and allowing to cool. The solidified fat cap will be cleaner. Repeat if needed. This does not remove all rancidity but improves the result significantly.

Calculating Fat-to-Lye Ratios

Different fats require different amounts of lye for complete saponification. This value is called the “saponification value” — the milligrams of potassium hydroxide needed to saponify 1 gram of fat.

Saponification Values (KOH mg per gram of fat)

Fat	SAP Value (KOH)	SAP Value (NaOH)
Beef tallow	197	140
Lard	198	141
Olive oil	190	135
Coconut oil	268	191
Sunflower oil	189	134
Palm oil	199	142
Castor oil	180	128

Always "superfat" your recipe by using 5-8% less lye than the calculated amount. This ensures no free lye remains in the finished soap (which would burn skin) and leaves unsaponified fat for moisturizing. In a survival context, err on the side of more superfatting (8-10%) — a slightly oily soap is far better than a caustic one.

Simple Calculation Example

For 1 kg of beef tallow with NaOH (sodium hydroxide):

• SAP value: 140 mg NaOH per gram of fat
• 1,000 g x 0.140 = 140 g NaOH needed
• With 8% superfat: 140 x 0.92 = 128.8 g NaOH
• Dissolve 129 g NaOH in roughly 350-400 ml water

Blending Fats for Better Soap

Single-fat soaps have predictable weaknesses. Blending compensates:

Beginner Blend (Widely Available Fats)

• 60% tallow or lard (hardness, stable lather)
• 25% olive oil (conditioning)
• 15% coconut oil (cleansing, lather boost)

All-Animal Blend

• 70% beef tallow (hardness)
• 30% lard (lather, conditioning)

All-Plant Blend

• 40% palm or coconut oil (hardness)
• 40% olive oil (conditioning)
• 20% sunflower oil (skin feel)

Common Mistakes

1. Using unrendered animal fat — raw fat contains water and proteins that cause soap to spoil, develop pockets, and smell bad. Always render thoroughly.
2. Too much coconut oil — above 30% in a recipe, coconut oil soap becomes aggressively drying and can irritate skin. Balance with conditioning oils.
3. Ignoring saponification values — each fat needs a specific amount of lye. Using a single ratio for all fats produces either caustic soap (too much lye) or greasy soap (too little lye).
4. Not superfatting — zero superfat means any measurement error leaves free lye in the soap. Always include a safety margin.
5. Discarding cooking grease — in a survival scenario, every scrap of fat has value. Collect and strain cooking oils and pan drippings for soap making.

Summary

Fat Selection — At a Glance

• Tallow (beef fat) is the benchmark soap fat: hard, white, stable, long-lasting
• Lard (pig fat) gives better lather and conditioning but slightly softer bars
• Coconut oil provides outstanding lather and hardness but is drying above 30% of a recipe
• Olive oil makes the mildest soap but requires long cure times and produces low lather
• Always render animal fats thoroughly — chop, melt slowly, strain, re-melt, strain again
• Calculate lye amounts using saponification values specific to each fat
• Superfat by 5-10% to ensure no free lye remains in the finished product
• Blend 2-3 fats for balanced soap: hardness + lather + conditioning