GB/T 26398-2017Evaluation guide of detergence,water costing and saving for laundry detergents—Simulated household washing test method (English PDF)

3.1 Wash

Wash refers to the process of removing stains adhering to clothes with an aqueous solution containing detergent.

NOTE: the aqueous solution containing detergent used in washing is known as wash solution.

3.2 Rinse

Rinse refers to the process of adding water to rinse clothes after washing.

3.9 Saving Water

Saving water refers to the degree of reduction in the level of using water of the sample detergent relative to the reference detergent after the completion of washing under determined washing comparison conditions.

6.1 Washing Lining (companion washing fabric)

The selection of washing fabrics for tests needs to consider the suitability with the determination of the evaluation results of the level of using water of the detergent. It shall also be close to the ratio of the mainstream fabrics in the market. Since different fabrics have different adsorption of laundry detergents, it is relatively reasonable to use a combination of fabrics with various typical materials for the washing tests. This combination may refer to the ratio of various fabrics worn by consumers daily. In addition, in accordance with the washing requirements, determine the quality of the fabrics to be washed at an appropriate quality. In the evaluation of the mode of washing by washing machines, use a set of washing lining fabrics with a net weight of 1,300 g […]

9.1 Detergency

After determining the test conditions of washing, enter the actual washing. […]

10.3 Application of Determination Indexes

For the determination of the rinsing effect, appropriate indexes shall be selected from the indexes listed in Table 1 to determine each rinse solution. The indexes selected for the tests should be involved in all three categories; they are also related to the formula of the detergent (for example, if an anionic surfactant is not added, then, it is unnecessary to test the indexes related to anionic surfactants) and can objectively reflect the rinsing effect.

The judgment of the end of rinse is determined by comparing the variation trend of the same type of indexes in the adjacent rinse solution. When the index of a certain rinse (the ith rinse) is significantly different from the same index of the previous rinse, while the relative change of the index of the following rinse is not obvious, then, it can be considered that the ith rinse has reached the actual demands, and the rinse can be terminated. In the specific test, the index of the ith rinse can be used as the base number to estimate the change ratios Ni-1 and Ni+1 of the indexes of the (i - 1)th rinse and the (i + 1)th rinse, so as to make the judgment of the rinsing result.

NOTE 1: the principle of determining the number (i) of rinses is that Ni-1 larger than 1, and Ni+1 smaller than 1 and close to 1. When Ni-1 is much larger than 1, and Ni+1 is much smaller than 1, it indicates that the rinse of the detergent needs to be continued, and that it needs to be re-calculated and re-evaluated in accordance with the data after the end of the next rinse.

NOTE 2: the deviation of the value of N from 1, and the difference between Ni-1 and Ni+1 are related to specific indexes. For different indexes, the magnitude of changes of the value of N is different. For some indexes (for example, anionic surfactant content), there may be an order of magnitude changes in the value of N; for some other indexes (for example, pH), the magnitude of changes of the value of N is relatively small; for some non-digital characterized items (such as: foam and turbidity), the value of N is based on manual estimation. The implementer of this Standard may combine the characteristics of the test samples and the indexes to determine the acceptable range of the value of N during the evaluation of rinse.

For the non-digital characterized items, a mode of estimating the value of N shall also be drawn up (for example, the amount of foam on the liquid surface of the solution or the size of foam on the liquid surface may be chosen as the basis for calculation; for the turbidity of the solution, unused rinse solution may be used as a benchmark for comparison).

NOTE 3: in order to effectively apply the value of N, the standard detergent listed in GB/T 13174 should be used for confirmation tests; the reference basis for the application of the value of N of each index in the laboratory shall be established.

11.1.4 Scanner method

Use a scanner to read the chromaticity value (Lab) of the stained cloth pieces before and after washing. Use Formula (1) to calculate the change of chromatic aberration DeltaEi of the stained cloth pieces before and after washing, so as to evaluate the detergency. Before and after washing, read the largest effective area of the center of the front side of the cloth pieces Lab1 and Lab2.

The value of chromatic aberration (DeltaEi) of a certain type of stain shall be calculated in accordance with Formula (1):

Where, L1i, a1i, b1i---the L, a and b value obtained through measurement of the ith stained cloth piece before washing;

L2i, a2i, b2i---the L, a and b value obtained through measurement of the ith stained cloth piece after washing.

NOTE: adopt a tablet scanner that complies with the stipulations of GB/T 18788 and equipped with working software that reads the Lab value of the images and calculates the chromatic aberration DeltaE. The scanner method is applicable to the evaluation of detergency of various colored stains. For detergents added with florescent whitening agents, the consistency between the test result by the scanner method and that of the manual visual inspection will be reduced.

11.2 Evaluation of Whiteness Preservation

In accordance with the whiteness change of the fabric material tested for whiteness preservation before and after washing by the sample detergent and the reference detergent, adopt the mode similar to the evaluation of detergency (11.1) to evaluate and calculate the whiteness preservation capability of the detergent.

A.1 Basic Principles for Selecting Types of Stain Used for Detergent's Performance Evaluation

Choose in accordance with the following modes:

a) Select stains that are representative and frequently appearing in people's daily lives;

b) The stain material shall be able to represent the originality of common stains in daily life and be applicable to laboratory evaluation;

c) The dyed stain material has good discrimination, as well as good stability and reproducibility;

d) Select the mainstream cloth in the market as the carrier, namely, cloth base, for the stain material preparation.

A.2 Classification of Stains

Classify stains in accordance with the following modes:

a) In accordance with the natural state of the stain source, the stains can be divided into solid stains, liquid stains and pasty stains;

b) In accordance with the representative types of stains in life, the stains can be divided into three types: food stains, household stains and environmental stains:

---Food stains mainly include: tea / coffee stains, wine stains, milk stains, edible oil stains, seasonings / sauce stains, fruits and vegetables / juice stains, grain food stains and infant food stains, etc.

---Household stains mainly include: sebum stains, blood stains, cosmetic stains, mineral oil stains, pen and ink stains, etc.

---Environmental stains mainly include: soot stains, soil stains and grass stains, etc. […]

A.3 Requirements for Quality