How to Use Acid Slurry (LABSA) to Make Liquid Soap and Detergent — Complete Guide for Indian Manufacturers

If you are a detergent manufacturer, a small-scale cleaning product maker, or someone just starting out in the liquid soap business in India — this guide is written specifically for you.

Every day, manufacturers across Nagpur, Vidarbha, Maharashtra and Central India ask the same questions:

• How do I use acid slurry (LABSA) to make liquid detergent?
• What is the correct ratio of LABSA to caustic soda?
• Why does my liquid soap turn lumpy or separate?
• How do I get the right pH in my final product?
• What is the difference between using LABSA and SLES?

This blog answers all of it — clearly, practically, and in the Indian context.

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What is Acid Slurry (LABSA)?

Acid Slurry is the trade name for Linear Alkyl Benzene Sulphonic Acid — LABSA. It is a brown, viscous liquid with a strong characteristic smell. It is the single most widely used raw material in the Indian detergent industry.

CAS Number: 27176-87-0

LABSA is produced by the sulphonation of Linear Alkyl Benzene (LAB) — a petroleum-derived compound. The sulphonation process uses Sulphur Trioxide (SO₃) or Oleum to produce LABSA.

In India, the most commonly available grades are:

Why is LABSA so important?

LABSA is the backbone of the Indian detergent industry because it is:

• Extremely cost-effective — lowest price per unit of active surfactant
• Available in bulk across India from manufacturers like IOCL, Tamilnadu Petroproducts, and Nirma
• Highly effective at removing grease, oil and organic soil
• Versatile — used in powder, liquid and bar detergents

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The Most Important Thing to Understand About LABSA

This is the single most common mistake made by new manufacturers. Raw LABSA has a pH of approximately 1–2. If you add it directly to your formulation without neutralisation:

• The product will be highly corrosive
• It will damage skin on contact
• It will corrode metal packaging
• The pH will be dangerously low
• Your product will fail any quality test

LABSA must always be neutralised with Caustic Soda (Sodium Hydroxide — NaOH) before use.

The neutralisation reaction converts LABSA (an acid) into LAS — Linear Alkyl Benzene Sulphonate — which is the actual active surfactant in your detergent. This is a permanent chemical change, not just a mixing step.

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The Chemistry — Simple Explanation

The neutralisation reaction is:

What this means in practice:

• LABSA (acidic, pH ~1) reacts with caustic soda (alkaline, pH ~13)
• They neutralise each other
• The product is LAS — a neutral or slightly alkaline surfactant
• The target pH for most liquid detergents is 7 to 9

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How Much Caustic Soda Do You Need to Neutralise LABSA?

This is the question every manufacturer asks. Here is the calculation:

In practical terms:

For every 8 kg of LABSA 96% — you need approximately 1 kg of caustic soda (100% NaOH).

But since caustic soda in India is commonly available as:

• Flakes (97–99% purity): use 1.03–1.05 kg per 8 kg LABSA
• Liquid lye (32% solution): use approximately 3 kg of liquid lye per 8 kg LABSA

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Step-by-Step Process: How to Neutralise LABSA and Make Liquid Detergent

Equipment You Need

• SS (Stainless Steel) mixing tank — minimum 200 litres for small batch
• Paddle stirrer or mechanical agitator
• pH meter or pH strips (range 0–14)
• Personal Protective Equipment — rubber gloves, safety goggles, apron
• Measuring containers (stainless steel or HDPE)
• HDPE drums or carboys for storage

Do NOT use aluminium or mild steel containers — caustic soda and LABSA both corrode these metals.

Safety Warning — Read Before You Start

LABSA is a Class 8 corrosive material (UN 2584). Caustic soda is also highly corrosive. When neutralising:

• Always wear rubber gloves, safety goggles and a full-length apron.
• Work in a well-ventilated area — neutralisation releases heat and some fumes.
• Never add caustic soda directly to LABSA — always prepare a caustic soda solution in water first.
• Keep running water nearby for emergency washing.
• If either chemical contacts skin — wash immediately with large amounts of water for 15 minutes.

Step 1 — Prepare Your Caustic Soda Solution

Never add dry caustic soda flakes directly to LABSA — this can cause violent splashing and heat generation.

1. Take a clean SS or HDPE container.
2. Measure the required quantity of soft water or RO water (hard water causes cloudiness).
3. Add caustic soda flakes SLOWLY into the water — never water into caustic soda.
4. Stir continuously as you add the flakes.
5. The solution will heat up significantly — this is normal (exothermic reaction).
6. Allow to cool to room temperature before use.
7. A typical working solution is 25–30% caustic soda in water.

Step 2 — Add LABSA to Your Mixing Tank

1. Add the required quantity of soft water to your mixing tank first.
2. Start the agitator/stirrer.
3. Add LABSA slowly into the water — never water into LABSA.
4. Stir at medium speed.
5. The LABSA will disperse and the mixture will become uniform.
6. At this stage the mixture is still acidic (pH 2–3).

Step 3 — Neutralise with Caustic Soda Solution

1. Begin adding your pre-prepared caustic soda solution slowly and gradually to the LABSA mixture.
2. Stir continuously throughout.
3. You will notice the mixture foaming — this is normal.
4. Add caustic soda in small portions — do NOT add all at once.
5. Check pH after each addition using pH strips or pH meter.
6. Target pH: 7.0 to 8.5 for most liquid detergents.
7. Stop adding caustic soda when you reach your target pH.
8. Allow to mix for 5 minutes after reaching target pH.
9. Check pH again — if it has risen above 9 add a small amount of citric acid to bring it down.

Important: The neutralisation reaction generates heat. If your batch heats above 50°C — stop adding caustic soda, let it cool, then continue. Overheating causes product instability.

Step 4 — Add SLES

1. Slowly add SLES (28% or 70% grade) to the mixture.
2. SLES does NOT need neutralisation — it is already a neutral salt.
3. Add while stirring continuously.
4. If using SLES 70% paste — warm it slightly for easier handling.
5. Typical addition: 10–20% of total batch weight depending on formulation.

The combination of LABSA (now neutralised to LAS) and SLES gives your liquid detergent its characteristic foam and cleaning power:

• LAS (from LABSA) — deep cleaning, grease cutting.
• SLES — fine foam, mildness, better skin feel.

Step 5 — Add Remaining Ingredients

In this order:

• CDEA (Coconut Diethanolamide) [2–5%] — Foam booster and thickener
• Salt (NaCl — common salt) [1–3%] — Viscosity thickener
• Glycerin [0.5–2%] — Moisturising agent for skin feel
• EDTA (Tetrasodium) [0.1–0.3%] — Chelating agent for hard water
• Preservative [0.05–0.1%] — Prevents microbial growth
• Fragrance [0.3–1%] — Scent (add after temperature drops below 40°C)
• Colour / Dye [0.01–0.05%] — Appearance

Step 6 — Final pH Check and Packaging

1. Allow mixture to cool completely to room temperature.
2. Check final pH — target 7.0 to 8.5.
3. Check viscosity — should be uniform, no lumps, no separation.
4. If too thin — add 1% salt solution slowly until desired thickness.
5. If too thick — add small amount of water with stirring.
6. Fill into HDPE bottles or carboys.

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A Basic Liquid Detergent Formula for 100 kg Batch

This is a standard formulation widely used by small and medium manufacturers in India:

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Common Problems and How to Fix Them

• 1. Product Turns Lumpy or Gels:
  Cause: LABSA added too fast, or water is too hard. Fix: Use soft/RO water, add LABSA slowly with continuous stirring.
• 2. Product Separates Into Two Layers:
  Cause: Incomplete neutralisation, or added SLES before full neutralisation of LABSA. Fix: Always complete LABSA neutralisation and check pH (7.0 - 8.5) before adding SLES.
• 3. pH Too High (Above 9):
  Cause: Excess caustic soda solution added. Fix: Add 10% citric acid solution slowly until pH falls to 7.5 - 8.5.
• 4. Viscosity Too Thin (No Body):
  Cause: Low CDEA or insufficient salt. Fix: Add 10% NaCl salt solution slowly (1% at a time), do not exceed 3% total salt.

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LABSA vs SLES — When to Use Which?

A question every manufacturer asks:

For most Indian small manufacturers: Use both together — LABSA provides cleaning power and cost efficiency, SLES provides foam quality and mildness.

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How to Check Quality of Your LABSA Before Use

• Appearance: Clear brown to dark brown viscous liquid with no solid sediments.
• Smell: Characteristic acid smell, no rancid or burnt odours.
• pH test: Dilute 1 ml in 100 ml water — pH should be 1.5 to 2.5.
• Active Matter: Ask for COA from supplier — should be 90% or 96% minimum.

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GST and Transport — Practical Notes for Buyers in Nagpur and Central India

LABSA attracts 18% GST in India. Sourcing locally from Nagpur-based distributors saves significant freight cost vs sourcing from Mumbai or Gujarat.

For buyers in Nagpur, Vidarbha, MP and Chhattisgarh — freight from Mumbai to Nagpur typically adds ₹2–4 per kg for drum quantities, whereas local pickup from Butibori MIDC has ₹0 freight cost.

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Where to Buy LABSA and SLES in Nagpur and Central India

FragVansh Aromatic Elements supplies LABSA 96%, SLES 28%, SLES 70%, and all other detergent raw materials from our warehouse at Butibori MIDC, Nagpur. We deliver pan-India with COA and MSDS provided for every batch.

You can request a quote or contact our sales team directly at the Contact Page.

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Frequently Asked Questions

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Summary — Key Points to Remember

• LABSA must always be neutralised with caustic soda before use.
• Add LABSA to water, never water to LABSA.
• Prepare caustic soda solution separately and let it cool before adding.
• Target pH for liquid detergent/floor cleaner: 7.0 to 8.5.
• Use soft/RO water to avoid cloudiness.
• Add SLES after LABSA is fully neutralised.
• Add fragrance below 40°C.
• Always verify with a pH meter.

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Disclaimer: The formulations and ratios provided in this blog are for general guidance only. Always conduct small-scale trials before full production. Consult a qualified chemical engineer for commercial-scale manufacturing. FragVansh Aromatic Elements is not liable for any outcomes resulting from the use of information in this article.