Liquid detergent detergency testing is a standardized laboratory evaluation that quantifies a detergent's ability to remove soils and stains from fabrics, dishware, and other surfaces under controlled washing conditions. By measuring whiteness recovery, soil removal rates, and anti-redeposition performance against reference detergents, manufacturers can verify product efficacy, substantiate marketing claims, and demonstrate compliance with national and international standards. This article explains the testing principles, sample types, evaluation items, methods, and practical applications of liquid detergent detergency testing.
Technical Overview
Detergency, also referred to as soil removal power or cleaning power, is the single most important performance attribute of any liquid detergent. Detergency testing measures how effectively a detergent solution removes artificially applied soils from standardized test substrates under reproducible laboratory washing conditions, and compares the result against a standard reference detergent.
The fundamental principle of detergency testing is straightforward: a soil layer is applied to a white fabric or dishware substrate, its initial reflectance is measured, the substrate is washed under strictly controlled conditions using the test detergent, and the reflectance is measured again. The increase in whiteness or reflectance is converted into a detergency value, which is then compared with the result obtained from a reference detergent washed in parallel. The most widely used whiteness metric is blue reflectance (R457, reflectance at 457 nm), measured with a calibrated whiteness meter or spectrophotometer.
Key testing standards and frameworks include:
- GB/T 13174 – Determination of detergency and anti-soil-redeposition property of laundry detergents, using artificially soiled standard test cloths and a comparison against a reference detergent.
- GB/T 13176 and related methods – Measurement of whiteness of powders and washed fabrics used in detergency evaluation.
- GB 9985 – Safety and technical requirements for hand dishwashing detergents, which specifies the plate-count detergency method.
- ISO 2267 – Surface active agents: evaluation of certain effects of laundering, including methods for preparation of soiled test cloths and washing procedures.
- ISO 6330 – Domestic washing and drying procedures for textile testing, used for full-scale machine washing studies.
- ASTM D4265 – Standard guide for evaluating stain removal performance in home laundering.
- AATCC TM 130 – Soil release: oily stain release method, used to assess detergent and fabric finishing performance on oily soils.
Testing is typically performed by accredited third-party laboratories, in-house research and quality control laboratories, or contract research facilities equipped with standardized washing equipment, controlled-temperature water systems, calibrated reflectance instruments, and certified reference materials.
Testing Samples
Liquid Laundry Detergents
This category includes standard liquid laundry detergents, concentrated and ultra-concentrated formulations, high-efficiency (HE) liquids for front-loading machines, liquid capsules, and specialty detergents for wool, silk, or colored fabrics. These products are evaluated on standard soiled fabric swatches to determine overall and stain-specific cleaning performance.
Hand Dishwashing Liquids
Manual dishwashing detergents are evaluated for grease removal capacity and foam endurance using artificially soiled plates or dishes, following the plate-washing approach defined in dishwashing detergent standards such as GB 9985.
Multi-Purpose and Specialty Liquid Cleaners
Liquid cleaners intended for hard surfaces, laundry pre-treatment (stain removers), or delicate fabrics may also undergo detergency or stain removal evaluations adapted to their intended use, often referenced to ASTM or ISO laundering guides.
Reference Materials
- Standard reference detergent (reference laundry powder or reference liquid) for parallel comparison washing.
- Certified artificially soiled test cloths, such as carbon black oily soil cloth, sebum/oily soil cloth, protein soil cloth, and pigment soil cloth, prepared in accordance with GB/T 13174 or ISO 2267.
- Unsoiled white control fabric for whiteness baseline and redeposition evaluation.
- Standard hard water prepared at defined calcium/magnesium hardness levels.
Testing Items
Typical evaluation items for liquid detergent detergency programs include:
- Detergency value (soil removal value): the percentage of soil removed by the test detergent, calculated from the reflectance increase of the soiled cloth after washing.
- Relative detergency ratio: the ratio of the test detergent's detergency value to that of the standard reference detergent washed under identical conditions; a ratio of 1.0 or higher is commonly required for compliance or premium claims.
- Whiteness maintenance and anti-redeposition: evaluation of how much removed soil redeposits onto clean white fabric during washing, indicating the detergent's soil-suspending capacity.
- Stain-specific removal performance: targeted evaluation against oily stains, protein-based stains (such as blood, egg, or milk), particulate soils, and colored stains.
- Grease removal capacity (dishwashing liquids): the number of soiled plates that can be effectively washed before foam collapse, or the measured removal of standardized artificial grease soil.
- Multi-cycle performance: repeated washing studies to assess cumulative whiteness retention, greying, and fabric incrustation.
Testing Methods
Standard Soiled Cloth Method (Primary Laundry Detergency Method)
This is the core method for liquid laundry detergent evaluation, generally aligned with GB/T 13174 and ISO 2267 principles. The procedure involves:
- Conditioning and pre-measuring the reflectance (R457) of certified soiled test cloths and unsoiled control fabric.
- Washing the soiled cloths together with clean white fabric in a laboratory washing device (bottle-type washing apparatus or laboratory drum washing machine) using defined water hardness, detergent dosage, liquor ratio, wash temperature (for example, 30 °C, 45 °C, or 60 °C), and wash duration.
- Running a parallel wash under identical conditions using the standard reference detergent.
- Drying, conditioning, and re-measuring the reflectance of all cloths.
- Calculating the detergency value from the whiteness increase of the test wash relative to the soil baseline, and the relative detergency ratio of sample versus reference.
A simplified expression of the calculation logic is: soil removal is proportional to the difference between post-wash reflectance and pre-wash reflectance of the soiled cloth, normalized against the reference detergent result obtained in the same run.
Anti-Redeposition Assessment
Clean white fabric swatches are washed together with the soiled cloths. The decrease in whiteness of the originally clean fabric after washing indicates how much removed soil has redeposited. A high-quality detergent formulation keeps the white fabric whiter, demonstrating effective soil suspension and anti-redeposition performance.
Machine Laundering Method
For performance claims tied to real-world conditions, full-scale laundering studies may be conducted using domestic washing machines operated per ISO 6330 procedures, with standardized stain panels or artificially soiled fabric loads. Stain removal is scored instrumentally by reflectance measurement or visually using gray scales and standardized lighting.
Stain Removal and Pre-Treatment Evaluation
Targeted stain matrices (oily, proteinaceous, particulate, and dye-based stains) are applied to fabric, treated with the liquid detergent according to prescribed protocols, and evaluated per ASTM D4265 or AATCC stain removal guides. These studies support specific on-pack stain claims such as grease, sweat, or coffee removal.
Plate-Washing Method for Dishwashing Liquids
Following the approach in GB 9985, plates are coated with a standardized artificial grease soil. The dishwashing liquid solution is prepared at a defined concentration and temperature, and plates are washed sequentially with uniform mechanical action until the foam layer collapses or the soil is no longer removed. The number of plates washed serves as the detergency index, with results compared against a defined reference threshold or a reference product.
Quality Assurance of Results
- All washing trials include the reference detergent run and replicate measurements to control run-to-run variability.
- Reflectance instruments are calibrated with certified white tiles, and fabric conditioning is performed at standard temperature and humidity.
- Interlaboratory comparison and proficiency testing are used by accredited third-party laboratories to ensure reproducibility.
Applications
Detergency testing data serves a wide range of commercial and regulatory purposes:
- Product development: comparing surfactant systems, builder packages, enzyme grades, and polymer additives to optimize formulation cost-performance.
- Quality control: verifying batch-to-batch consistency against established performance benchmarks before market release.
- Regulatory compliance: demonstrating conformance with national detergent standards and technical specifications for market access, including mandatory requirements in certain jurisdictions.
- Claim substantiation: providing laboratory evidence for marketing claims such as superior stain removal, concentrated performance, cold-water efficacy, or whiteness retention.
- Benchmarking: head-to-head comparison against competitor or reference products to support positioning and retail negotiations.
- E-commerce and procurement qualification: supplying third-party test reports required by retail platforms, institutional buyers, and export customers.
FAQ
Q: What is a detergency value and how is it interpreted?
A: The detergency value expresses the degree of soil removal achieved by a detergent, derived from the increase in fabric reflectance after washing under standardized conditions. A higher value indicates stronger cleaning power. For compliance and comparison purposes, the relative detergency ratio against a standard reference detergent is the decisive figure; a ratio of 1.0 or above indicates performance equal to or better than the reference.
Q: Which standards govern liquid detergent detergency testing?
A: Laundry detergents are primarily evaluated under GB/T 13174 with supporting procedures in ISO 2267, ISO 6330, ASTM D4265, and AATCC methods. Hand dishwashing liquids are commonly assessed under GB 9985 using the plate-washing method. The applicable standard depends on the product type and target market.
Q: What sample quantity and sample preparation are required?
A: A typical detergency program requires several hundred milliliters to one liter of liquid detergent, depending on the number of soil types, temperatures, and replicate conditions requested. Samples should be homogeneous, properly labeled, and accompanied by dosage instructions reflecting real-use conditions.
Q: How are different soil types addressed?
A: Certified soiled cloths representing carbon black oily soil, sebum-type oily soil, and protein soil are washed in parallel. This matrix reveals whether the detergent is a general-purpose cleaner or excels against specific soil classes, which is essential for enzyme-containing and targeted formulations.
Q: Can dishwashing liquids be tested with the fabric method?
A: No. Hand dishwashing liquids are evaluated with the plate-washing or grease removal approach defined in dishwashing standards, because their function depends heavily on foam stability and emulsification of grease rather than fabric whiteness recovery.
Q: How long does detergency testing take?
A: A standard single-temperature, three-soil-type evaluation with a reference comparison is usually completed within one to two weeks, including fabric conditioning and replicate runs. Multi-cycle, multi-temperature, or machine-washing studies require additional time.
Q: What does a typical test report include?
A: Reports from accredited third-party laboratories typically include sample identification, applied standards and methods, washing conditions (temperature, water hardness, dosage, liquor ratio), reflectance data before and after washing, calculated detergency values, the relative detergency ratio versus the reference detergent, anti-redeposition results where applicable, and a clear conclusion on performance.