Manufacture Of Dishwashing Liquid with Use Of Caustic Soda

Manufacture Of Dishwashing liquid with caustic soda means neutralizing an acidic surfactant (usually LABSA) to the right pH, blending primary and secondary surfactants, adjusting viscosity with salt and solvents, then cooling, filtering, and packing under strict safety, quality, and regulatory controls to deliver stable, high-foaming, skin-compatible products.

Modern dishwashing liquids look simple on the shelf, but behind each bottle sits a carefully controlled chemical process. If you work in detergents manufacturing, private label production, or are planning a new plant, understanding the role of caustic soda is essential for safe and efficient production.

Process Overview for the Manufacture Of Dishwashing Liquid with Caustic Soda

At a high level, the process is a neutralization and blending operation carried out under controlled mixing, temperature, and pH:

1. Charge water into a mixing tank and start agitation.

2. Add LABSA (linear alkyl benzene sulfonic acid) and pre-dissolve.

3. Neutralize with caustic soda solution to convert LABSA to its sodium salt (LAS) and bring pH into the target range.

4. Add secondary surfactants such as SLES, SLS, CAPB, and nonionics (e.g., CDEA).

5. Adjust viscosity and feel using salt, solvents (e.g., propylene glycol), and humectants (e.g., glycerin).

6. Add minors: preservatives, color, fragrance, and any specialty additives.

7. Top up with water, fine-tune pH and viscosity, then filter and fill.

Typical Ingredient System

Below is a simplified view of a common hand dishwashing liquid base (manual dishwash, not machine dishwasher):

Exact levels depend on local regulations, target cost, desired performance, and the active matter of each raw material.

Key Raw Materials and the Role of Caustic Soda

Surfactant Backbone

In most hand dishwashing liquids:

• LABSA provides strong grease cutting, but is acidic and irritating in its raw form. It must be neutralized to its sodium salt.

• SLES and SLS add high foam and detergency; SLES is milder and widely used in household products.

• CAPB (cocamidopropyl betaine) improves foam stability and mildness, especially valuable in hand-contact products.

• Nonionic surfactants such as CDEA help cut greasy soils and boost foam, but must be dosed within regulatory and safety limits.

Where Caustic Soda Fits In

Caustic soda (sodium hydroxide, NaOH) plays three main roles:

• Neutralization: It converts LABSA to LAS, the actual anionic surfactant that cleans dishes.

• pH Adjustment: It brings final pH into the typical 6.5–8.0 window—high enough for cleaning, low enough for skin compatibility and stability.

• Performance and Stability Tuning: Slight pH adjustments influence grease-cutting efficiency, perfume stability, and even preservative performance.

Common practice is to use a 30–50% NaOH aqueous solution, added slowly under agitation while monitoring pH and temperature. Safety data sheets classify liquid caustic soda as corrosive, requiring robust PPE and handling procedures.

Step-by-Step Production: Practical 1,000 kg Batch Tutorial

Below is a typical batch workflow for a 1,000 kg manual dishwashing liquid. Adapt equipment capacities, safety factors, and process parameters to your plant.

1. Preparation and Safety

• Verify that the tank, agitator, and transfer lines are clean and labeled.

• Confirm raw material identity and lot numbers.

• Prepare caustic soda solution (e.g., 30–35%) in a separate, vented tank by adding NaOH flakes/solution into water, never the reverse.

• Ensure operators wear face shields, gloves, aprons, and use local exhaust when handling LABSA and NaOH.

2. Charge Water and Dissolve LABSA

1. Add ~60–70% of the batch water to the main tank.

2. Start agitation and, if needed, heat to 30–40 °C for better dissolution.

3. Slowly add LABSA, avoiding splashing, until fully dispersed and homogeneous.

3. Neutralize with Caustic Soda

• Begin dosing the NaOH solution slowly, maintaining good agitation.

• Monitor pH continuously; initial target after full neutralization is pH 7.0–7.5 at 25 °C.

• Control temperature (exothermic reaction) to avoid darkening or degradation of the surfactant.

A simplified view of this early-stage process:

4. Add Secondary Surfactants

Once neutralization is complete and temperature is under control:

• Add SLES/SLS slowly to avoid excessive foam.

• Add CAPB and nonionics such as CDEA.

• Maintain mixing until the solution is clear and uniform.

5. Adjust Viscosity and Add Functional Additives

1. Dissolve sodium chloride in a small portion of water and add gradually, watching viscosity.

2. Add solvents (propylene glycol, etc.) and humectants (glycerin) to fine-tune clarity and freeze–thaw stability.

3. Introduce preservative according to supplier guidelines.

4. Add perfume and color last to minimize loss and shade drift.

6. Final Adjustments, Filtration, and Filling

• Top up to the final batch weight with water.

• Recheck pH, viscosity (e.g., Brookfield), and appearance.

• Correct pH with tiny additions of NaOH (up) or a compatible acid (down), and viscosity with more salt or water.

• Filter through a suitable mesh to remove undissolved particles.

• Fill into clean, labeled containers using calibrated filling lines.

Safety and Regulatory Controls for Caustic Soda

Using caustic soda safely is absolutely non-negotiable.

Handling and Storage

• Classify and label according to GHS/CLP: caustic soda is corrosive (H314) with severe skin and eye damage risk.

• Store NaOH solutions in corrosion-resistant tanks with secondary containment.

• Keep away from acids, aluminum, and incompatible organics.

• Provide eyewash stations and safety showers near handling points.

Mixing Rules

• Always add NaOH to water, not water to solid NaOH.

• When neutralizing LABSA, maintain agitation and slow addition to avoid localized high pH and thick “gels.”

• Control temperature rise and use cooling if needed.

Regulatory and Documentation

• Maintain SDSs for all raw materials and finished products.

• Ensure compliance with detergent regulations and environmental labeling criteria in your target markets (e.g., EU Detergent Regulation, national eco-label schemes).

Quality Control, Testing, and Optimization

Robust QC differentiates a professional manufacturer from a blender of cheap formulas.

Core QC Tests for Dishwashing Liquids

Data-Driven Optimization

In practice, many plants now:

• Use designed experiments (DoE) to explore how surfactant ratios, salt, and caustic dosing affect viscosity and cleaning.

• Track batch data digitally and leverage simple analytics or AI tools to predict when a formula will fall out of spec.

• Run panel tests comparing their product to leading brands on foam, feel, fragrance, and residue.

Formulation Variants: Economy, Standard, and Premium

Different markets require different balances of cost, performance, and mildness. Caustic soda usage adjusts accordingly because it must fully neutralize the acidic surfactant component.

Example Formulation Ranges (Conceptual Only)

When you increase LABSA to cut cost, you must:

• Increase NaOH to achieve full neutralization.

• Keep a close eye on pH and skin mildness.

• Possibly add more CAPB or other mild surfactants to compensate.

Conversely, more SLES/CAPB and less LABSA often means less caustic, but higher raw material cost and better mildness perception.

Sustainability Trends and Innovation in Dishwashing Liquids

The manufacture of dishwashing liquids is changing rapidly under regulatory and consumer pressure.

Key Trends

• Shift to bio-based surfactants: New biosurfactants from fermentation and plant sources aim to match performance while improving biodegradability and reducing toxicity.

• Eco-friendly dish soaps: Brands are highlighting phosphate-free, dye-free, and fragrance-limited options, along with recycled or lightweight packaging.

• Concentrated and solid formats: Higher active matter reduces shipping costs and plastic usage but demands precise control of caustic dosing and pH to keep products stable.

Manufacturers that adapt formulations to use milder surfactants, optimized caustic levels, and greener raw materials are better positioned to obtain eco-labels and win B2B contracts with sustainability goals.

Commercial and Scale-Up Considerations

Moving from lab or pilot batches to full industrial manufacture Of Dishwashing liquid requires more than a good formula.

Key points to manage:

• Supply chain: Secure reliable sources of LABSA, NaOH, surfactants, and preservatives with consistent specs.

• Process design: Decide on batch vs. semi-continuous systems, material flow (gravity vs. pump transfer), and automation level.

• Energy use: Optimize mixing speeds, heat exchange, and CIP cycles to cut operating costs.

• Contract manufacturing: For private-label buyers, define detailed quality agreements including pH, active matter, and packaging tests.

A practical approach is to standardize one or two versatile bases (e.g., standard and premium), then customize perfume, color, and minor additives per customer.

Troubleshooting Common Issues

A focused troubleshooting table can save many off-spec batches.

Practical Checklist for Manufacturers (Executive Summary)

Use this checklist as a quick audit tool for your manufacture Of Dishwashing liquid with caustic soda:

• Raw Materials

  • Defined surfactant system (LABSA + SLES/SLS + CAPB/nonionics).

  • Verified SDSs and certificates of analysis for each input.

• Formulation Design

  • LABSA level matched with calculated NaOH requirement.

  • Target pH range, viscosity, and active matter clearly specified.

• Process Control

  • Water → LABSA → NaOH neutralization sequence validated.

  • Mixing times, speeds, and temperatures documented.

  • Clear SOPs for salt and minor additions.

• Safety & Compliance

  • Appropriate PPE, eyewash, and showers in place.

  • Tanks and drums labeled with corrosive hazard symbols.

  • Compliance with detergent regulations and eco-label criteria where applicable.

• Quality & Optimization

  • Routine QC tests: pH, viscosity, appearance, foam, cleaning performance, and microbiology.

  • Stability and shelf-life data for each SKU.

  • Continuous improvement loop for cost, performance, and sustainability (e.g., trialing bio-based surfactants).

If these boxes are ticked, you are well positioned to produce consistent, competitive dishwashing liquids that meet customer expectations and regulatory demands.

FAQs on Dishwashing Liquid Manufacturing with Caustic Soda

1. Why is caustic soda used instead of another alkali in dishwashing liquids?
Caustic soda offers strong, predictable alkalinity and high solubility, making it ideal for neutralizing LABSA and adjusting pH. Other alkalis like sodium carbonate can be used, but NaOH allows finer control at lower dosages and is widely available industrially.

2. What pH range is recommended for hand dishwashing liquids?
Most manual dishwashing liquids target a pH between about 6.5 and 8.0 at 25 °C. This keeps cleaning performance high while reducing irritation potential and preserving fragrance and color stability over shelf life.

3. How do I calculate the amount of caustic soda needed to neutralize LABSA?
You start from the acid’s active matter and its equivalent weight, then calculate the stoichiometric NaOH required, adding a small excess for practical losses. Suppliers often provide neutralization curves; pilot batches are still essential to fine-tune the exact dose.

4. Can I produce “green” dishwashing liquids while still using caustic soda?
Yes. Many eco-labeled products still use caustic soda for pH control but combine it with bio-based surfactants, biodegradable solvents, and optimized packaging. The key is overall environmental profile, not the exclusion of every inorganic ingredient.

5. Why does my dishwashing liquid become too thick after adding salt?
Salt strongly affects micelle structure and can cause a sharp viscosity peak. If you overshoot that peak, the system may gel. Always add salt in small increments, under good mixing, and record addition curves for each formula.

6. How important is water quality in the manufacturing process?
Very important. Hard or contaminated water can change viscosity, create haze, and reduce cleaning performance. Most plants use softened or deionized water, especially at the neutralization and final makeup stages, to keep batch-to-batch behavior consistent.

7. What are typical shelf-life targets for dishwashing liquids?
Many brands aim for 24–36 months under normal storage conditions. Achieving this requires robust preservation, packaging compatibility, and stability against temperature cycles, light exposure, and perfume oxidation.

8. How can I benchmark my product against leading brands?
Combine lab tests (foam height, foam stability, detergency, pH, viscosity) with panel tests where trained or consumer panels wash standardized soiled dishes. Compare results blind against at least two or three market leaders in your segment.

9. Are there special considerations for highly concentrated dishwashing liquids?
Concentrates require more precise control of surfactant ratios, caustic dosing, and salt levels to avoid phase separation or crystallization. Perfume and dye selection also becomes more critical because they interact more strongly at higher actives.

10. What’s the best way to scale from a 10 kg lab batch to a 1,000 kg production batch?
Maintain ingredient ratios and process sequence, but reassess mixing times, shear levels, and heat transfer. Perform at least one intermediate pilot batch, and validate that pH, viscosity, and foam match the lab standard before full commercialization.

Sources

1. American Cleaning Institute – Soaps and Detergents: Making Everyday Cleaners
   Technical booklet explaining surfactants, builders, and basic detergent manufacturing principles for household products.
    cleaninginstitute.org

2. Gad Elmawla A. – Improved Manual Dishwashing Liquid Detergent Formulations (Egyptian Journal of Chemistry, 2018)
   Research article examining how LABSA/SLES ratios and electrolyte levels influence viscosity, foaming, and cleaning performance in manual dishwash liquids.
    ejchem.journals.ekb.eg

3. Patil H.V. et al. – Sustainable bio-based surfactants: Advances in green chemistry (2025)
   A modern scientific review on biosurfactants, covering performance, biodegradability, and their use in eco-friendly detergent formulations.
    ScienceDirect

4. Chemfax – Sodium Hydroxide (Liquid) Safety Data Sheet (2021)
   Authoritative SDS detailing hazards, handling guidelines, and emergency measures for liquid caustic soda used in soaps and detergents.
    chemfax.com