Soap Varieties

Part of Soap Making

An overview of the different soap types you can make and how to choose based on available ingredients and intended use.

Why This Matters

Not all soap is the same. The type of alkali you use, the fats you combine it with, and any additives you incorporate produce wildly different results — from crumbly laundry bars that strip grease off cloth to gentle shaving creams that cushion a blade. Understanding the landscape of soap varieties means you can match your production to your actual needs and available materials rather than making one generic product for every purpose.

In a rebuilding context, soap is not a luxury — it is a disease-prevention tool. Cholera, dysentery, and skin infections kill more people in collapse scenarios than almost anything else, and regular handwashing with soap breaks those transmission chains. Getting your soap-making right, and producing the right types for the right jobs, is a public health priority.

The good news is that the core chemistry is the same across all soap varieties. Saponification — the reaction between an alkali and a fat — produces soap and glycerin every time. What changes is which alkali, which fat, in what ratio, and what you add afterward. Once you understand those levers, you can produce a full spectrum of cleaning products from a basic setup.

The Alkali Determines the Form

The single most important variable in soap type is the alkali used:

Sodium hydroxide (NaOH) produces hard bar soap. NaOH is obtained commercially or synthesized via the lime-soda process (see Hard Bar Soap). Hard bars last longer, travel better, and are preferred for personal bathing and shaving.

Potassium hydroxide (KOH) produces soft or liquid soap. KOH is what you get naturally from wood ash lye — it is the easier alkali to produce from scratch. Soft soap has a paste or gel consistency and is diluted with water for liquid applications. This is the historically dominant homemade soap type and remains the easiest to produce without industrial inputs.

Mixed alkali — combining NaOH and KOH — produces semi-solid soaps with intermediate properties. Traditional shaving soaps often use a blend to achieve a dense, creamy lather that softens beard hair effectively.

Wood ash lye gives you KOH by default. If you only have wood ash lye, your natural product is soft/liquid soap. To produce hard bars from scratch requires additional chemistry — specifically the salt-out method or the lime-soda process. Plan your soap program around what alkali you can actually produce.

Hard Bar Soap (NaOH-Based)

Hard bar soap is the familiar solid brick used for personal bathing. It is produced by reacting sodium hydroxide with fats at a ratio of roughly 1 part NaOH to 3-6 parts fat by weight, depending on which fats are used.

Best fats for hard bars: Tallow (beef or mutton fat) and lard (pork fat) produce firm, long-lasting bars with moderate lather. Coconut oil makes an exceptionally hard, fast-lathering bar but can be drying at high percentages — keep coconut oil below 30% of the fat blend. Palm oil (if available) produces hardness similar to tallow.

NaOH saponification values (grams of NaOH needed per 100g of fat):

• Tallow: 14.0g NaOH
• Lard: 13.8g NaOH
• Coconut oil: 19.0g NaOH
• Olive oil: 13.4g NaOH

A classic tallow bar: 500g tallow, 70g NaOH, 190ml water. Produces a white, firm bar with mild lather and exceptional longevity.

For full details on hard bar production from scratch, see Hard Bar Soap.

Soft and Liquid Soap (KOH-Based)

Soft soap is the natural product of wood ash lye saponification. The paste produced is concentrated and must be diluted with water to create liquid soap suitable for handwashing and general cleaning.

Best fats for soft/liquid soap: Olive oil, linseed oil, and other soft oils produce a gentle, slow-lathering liquid soap well suited to skin contact. Coconut oil can be added (up to 20%) to increase lather speed. Avoid high percentages of hard fats (tallow, coconut) in liquid soap — they cause cloudiness and may gel at cool temperatures.

Soft soap is better for laundry and dishwashing than personal bathing, partly because it rinses less cleanly and partly because the glycerin content makes it feel slightly sticky on skin compared to properly cured hard bar soap.

For full production details, see Liquid Soap.

Castile Soap

Castile soap is made from 100% olive oil — no other fats. Originating in the Castile region of Spain, it is one of the oldest documented soap formulas still in wide use.

Properties: Extremely gentle on skin. Produces a slippery, low-bubble lather that feels luxurious but does not look foamy. Very slow to cure — requires 4-6 weeks minimum before use, ideally 6-12 months for optimal mildness. Soft and somewhat sticky when fresh; firms significantly with extended curing.

NaOH ratio: 500g olive oil requires 67g NaOH and 190ml water for a cold-process batch.

Why it matters in a rebuild: Olive trees are widespread in Mediterranean climates and olive oil can be produced at village scale. A community with olive trees has a sustainable luxury soap supply. Castile soap is also safe for infants and people with sensitive skin conditions.

Limitation: True castile requires abundant olive oil, which is a food resource. In scarcity, blending olive oil with cheaper fats (tallow, lard) produces a reasonable alternative — traditionally called “Marseille soap” when made with 72% olive oil and 28% coconut/palm.

Laundry Soap

Laundry soap prioritizes cleaning power over gentleness. Skin contact is minimal (hands, occasionally) so the formula can be more aggressive.

Formula approach: High coconut oil percentage (50-80%) for strong surfactant action and fast lather. Higher alkali ratio (slight lye-heavy formula) to leave residual alkalinity that helps lift stains. Some producers deliberately superfat at 0% (no excess fat) or even add a small excess of alkali for maximum cleaning power — do not do this for skin soap, only for laundry use.

Production method: Hard bar format (NaOH) is most practical for laundry — the bar is grated or shaved into hot wash water. A softer KOH laundry soap paste can be dissolved directly in water.

Additives: Washing soda (sodium carbonate, Na2CO3) is often added to laundry soap to boost alkalinity and water softening. Add after saponification as a powder mixed into the soap batter before pouring. Ratio: up to 20% washing soda by total batch weight. Borax (sodium tetraborate) performs similarly if available.

Scent/additives: Unnecessary for laundry soap. Skip essential oils and botanicals — they add cost and complexity without cleaning benefit.

Medicated Soap

Medicated soap incorporates antimicrobial or healing botanicals into a standard soap base. This bridges personal hygiene and basic medicine.

Effective botanicals to incorporate:

• Calendula (pot marigold): Anti-inflammatory, wound-healing. Use dried flowers infused in the fat before soap-making (infuse 2-4 weeks in olive oil, strain). Gentle enough for damaged skin.
• Neem (Azadirachta indica): Antifungal, antibacterial, antiparasitic. Use neem oil as part of the fat blend (10-30%). Strong smell but highly effective for skin infections, scabies, ringworm.
• Tea tree (Melaleuca alternifolia): Broad-spectrum antimicrobial. Add essential oil at trace (1-3% of total batch weight). Not a soap-making region staple, but worth noting.
• Pine tar: Traditional medicated additive used for eczema, psoriasis, and scalp conditions. Add 5-15% pine tar to soap batter at trace. Has a strong, distinctive smell that many find pleasant. Pine tar is produced as a byproduct of pine charcoal making — a useful secondary product.
• Activated charcoal: Add finely powdered activated charcoal (1-2 teaspoons per 500g fat batch) to the soap batter. Adsorbs toxins, bacteria, and sebum. Makes a striking black bar that is popular for acne and oily skin.

Method: For fat-soluble botanicals (neem oil, infused oils), incorporate them directly into the fat component before making lye solution. For powdered additives (charcoal, ground herbs), add at trace — the point where the soap batter has thickened enough to hold additions without sinking.

Scouring Soap

For heavy-duty cleaning — greasy tools, blacksmithed metal, heavily soiled hands after field work — a scouring soap includes abrasive particles that mechanically lift grime.

Abrasives to incorporate:

• Fine sand: Washed, dried, sieved to remove large particles. Add at trace, 1-3 tablespoons per 500g fat batch. Too much makes soap crumbly.
• Pumice powder: Volcanic rock ground fine. Superior to sand — lighter, more consistent particle size, slightly porous so it holds lather. Add 2-4 tablespoons per batch.
• Cornmeal or oatmeal: Softer abrasion, suitable for moderately dirty hands and gentle exfoliation. Add 3-4 tablespoons per batch.
• Ground walnut shell: Medium abrasion, pleasant texture. Good for mechanics or anyone working with grease and oil.

Formula considerations: Use a harder fat blend (tallow-dominant) for scouring soap so the bar holds together under friction without dissolving too quickly. Higher coconut oil (25-30%) improves lather despite the abrasive load.

Application: Wet hands, rub bar vigorously, work up lather before scrubbing. Do not use scouring soap on face or sensitive skin.

Shaving Soap

Shaving soap must produce a dense, stable, lubricating lather that cushions the blade and softens facial hair. It differs fundamentally from bathing soap in texture and performance requirements.

Alkali: Mixed NaOH/KOH (approximately 60% KOH / 40% NaOH by alkali weight) produces the classic semi-soft consistency. Pure KOH makes too soft a product; pure NaOH makes too hard a bar that does not load onto a brush easily.

Fat selection: Stearic acid-rich fats produce the dense, stable lather required. Best options:

• Tallow (high stearic content) — the traditional base
• Lard — similar to tallow, slightly softer result
• Coconut oil (15-20% of blend) — adds lather volume and speed
• Castor oil (5-10% of blend) — exceptional lather booster, adds creaminess; the single most useful shaving soap additive

A simple shaving soap formula (500g fat total):

• 350g tallow
• 100g coconut oil
• 50g castor oil
• 116g KOH (90% purity) + 58g NaOH
• 210ml distilled water

Method: Hot process is preferred for shaving soap — cook to full saponification (2-3 hours in a double boiler or slow cooker), then pack into a wide-mouth container while warm. Allow to firm 2-4 weeks. Load with a wet shaving brush to create lather.

No fragrance required — unscented shaving soap is effective and avoids skin irritation during shaving when the skin barrier is compromised by the blade.

Saddle and Leather Soap

Leather soap cleans, conditions, and preserves leather goods — saddles, boots, belts, harnesses, bags. It is less alkaline than bathing soap (high superfatting leaves excess conditioning oils) and contains additional conditioning agents.

Formula approach: Superfat at 15-20% (much higher than the standard 5-8% for bathing soap). This means the alkali is calculated to saponify only 80-85% of the fat, leaving free oils to condition the leather.

Fat selection: Include beeswax (5-10% of formula), neatsfoot oil (from cattle leg bones and feet — traditionally used for leather conditioning), and lanolin (from wool) if available. These penetrate leather effectively.

A basic leather soap formula:

• 400g tallow
• 50g beeswax (melt with fats)
• 50g neatsfoot oil or lard
• 52g NaOH (calculated for 80% saponification of the fat blend)
• 150ml water

Use: Dampen a cloth or sponge, rub on the bar to pick up soap, work into leather in circular motions, wipe off excess with a dry cloth. Do not saturate leather — work in thin layers.

Choosing the Right Type

Need	Best Type	Alkali
Personal bathing	Hard bar or castile	NaOH (or KOH salt-out)
Handwashing (liquid)	Liquid/soft soap	KOH (wood ash lye)
Laundry	Laundry bar or paste	NaOH or KOH
Dishes	Liquid soap	KOH
Skin infections	Medicated (neem/calendula)	NaOH or KOH
Heavy work	Scouring bar	NaOH
Shaving	Shaving soap	Mixed NaOH/KOH
Leather care	Leather soap	NaOH (high superfat)

In a resource-constrained rebuild, start with liquid soap from wood ash lye — it requires the least infrastructure and covers the most critical needs (handwashing, laundry, dishes). Graduate to hard bars once you can produce or obtain NaOH reliably.

Common Mistakes

• Using the same formula for laundry and personal bathing — laundry soap is too stripping for skin
• Adding botanicals before trace — they sink to the bottom or get destroyed by the hot lye
• Making shaving soap with pure NaOH — it will be too hard to load onto a brush
• Superfatting laundry soap — excess free oils leave grease stains on fabric
• Using coarse sand in scouring soap without sieving — large grit scratches rather than scours
• Confusing KOH and NaOH soap appearance — KOH soap is always translucent/soft when fresh, not a sign of failure

Key Takeaways

• The alkali (NaOH vs KOH) is the primary determinant of soap form: NaOH = hard bar, KOH = soft/liquid
• Wood ash lye naturally produces KOH — liquid soap is the easiest type to make from scratch
• Fat selection controls hardness, lather quality, and skin feel
• Different soap types serve different purposes — a single formula is a compromise
• Additives (botanicals, abrasives, wax) are incorporated at trace after saponification begins
• Superfatting percentage controls harshness: 0% for laundry, 5-8% for bathing, 15-20% for leather soap