Abstract

A standard method for the evaluation of hand dishwashing products, adapted to Italian conditions, was developed and checked for robustness and reliability. The stability of the method, the ability to differentiate the results in various conditions, and the simplicity of its implementation are useful characteristics of the method.

In the context of the activities carried out by companies in the detergency sector, the evaluation of the “performance” of the product has a very significant value.

Over the years, other protocols have been developed internationally which in many cases have also been used in Italy as a reference by companies which, however, increasingly often have highlighted their limitations, both linked to execution difficulties and criteria not always correlated with the national reality.

For these reasons, companies in the detergency sector have expressed the need to develop alternative, possibly standardized methods for evaluating the “performance” of some categories of cleaning products, closer to the reality and habits of Italian consumers.

Within Assocasa (National Association of Detergents and Specialties for Industry and the Home) which is part of Federchimica, a dedicated Working Group was set up for this purpose which also saw the precious collaboration of Innovhub SSI (Stazioni Sperimentali for industries).

After careful evaluation, the Working Group identified some categories of products for which a need in this sense could be identified, among which priority was given to products for hand cleaning of dishes.

About the category mentioned, it was considered useful to develop a new evaluation standard as the most widely used protocol among the existing ones, prepared and published by IKW, the German association of detergent manufacturers presents many application difficulties. In addition to the complexity of execution, the type of “dirty” defined by IKW is based on ingredients that are difficult to find in Italy (mostly linked to the habits of German consumers) making it difficult to apply.

The Working Group, starting from a careful analysis of the existing methods and in particular of the IKW already mentioned, provided for the preparation of a simplified standard with specific regard to the preparation of the soiling mixture, more widely adapted to the national context and, at the same time, with easier possibility to find ingredients required for the execution, and greater robustness.

Coordinated by Innovhub SSI, some laboratories of the member companies have also validated the method in practice through a series of inter-laboratory tests (Ring Test) carried out several times.

The demonstration of the stability of the method, the ability to differentiate the results in various conditions and the simplicity of its implementation allow, according to the Working Group, that the method can become a useful reference for the sector.

METHODOLOGY
Federchimica-Assocasa method developed with the collaboration of “Innovhub - Stazione Sperimentale per le industrie degli Oli e dei Grassi”.

1. Scope
   This is a method for the determination of the cleaning performance of hand dishwashing detergents.
2. Normative References
   Recommendation for the Quality Assessment of the Cleaning Performance of Hand Dishwashing Detergent (Ch. Nitsch,G. Huttmann) SOFW-Journal,128 Jahrgang 5-2002
   (2011/382/EC) Ecological criteria for the award of the Community eco-label to hand dishwashing detergents
3. Principle
   In a dishwashing solution soiled plates are washed by hand until the foam layer collapses. Besides the dishwashing detergents for testing, may be conducted a control with a reference detergent (ref. point 8).
4. Reagents
   
   Water (soft water is to be prepared by dilution of tap water with demineralized water on the base of the tap water hardness measured).

Soil: see table 1 for composition.
Testing samples.

5. Apparatus
Plates (melamine, diameter 20 cm).
Washing up basin (inner diameter 30cm).
Water reservoir with outlet tap (5 liters capacity).
Washing up sponge/brushes, bi-color, brush and sponge, ergonomic, see image 1 in as an example
Disposable pipettes.
Balance (precision 0.1g).
Heater with magnetic stirrer.

6. Procedure

Soil preparation

• All the components are separately weighted.
• Premix oleic acid, stearic acid and sunflower oil melting them.
• Add flour to 1/3 of the water (demineralized) pre-heated at 60 + 3°C stirring by using a mixer till obtaining a smooth paste.
• Add the fatty premix to the hot water + flour, stirring by using a vertical mixer to a smooth paste.
• Add to the mix (stirring) the rest of the water (demineralized) pre-heated at 100 + 5°C.
• Half of the soil is left boiling (low heat) for about 2 minutes, stirring.
• Add the other half part of the soil and let it cool at room temperature, without forcing it (minimum of three hours are necessary). When cold, filter the soil using a kitchen strainer.
• When soil is stored overnight, seal the container and keep it cool in the fridge (4 + 2°C).
• This soil can be stored in freezer up to one month.

Soiling the plates

• In order to have clean plates wash them using a common automatic dishwasher (normal program. Temperature 50-65°C) with 1/3 of the dosage of a common detergent.
• Put a dry and cold plate on balance.
• Use disposable pipettes to dispense the amount of soil (5 g ± 0.1g ) onto each plate.
• Spread using the back side of a spoon the soil evenly over the front surface of each plate.
• Age the soil at least 10 minutes (letting it drying on the surface)
• Stack the plates at the side of the washing-up basin.

Execution of the test

• Put the required amount (g) of product (agreed with the customer) directly in the washing-up basin using a balance and note the exact dosage (precision of 0.1g).
• Put the washing-up basin on the floor and add the water (generally 3 liters) at the required temperature (agreed with the costumer) using the reservoir positioned with the outlet tap at a fixed height that have to be set at least 70 cm above the floor (maximum 1 meter). This generates the lather. The starting temperature of the water must be the same for all the replications. A decreasing of the water temperature during the execution of the test is acceptable also in order to reproduce the real domestic condition of execution of the washing phase. As the conduction of the removal phase is standardized it is possible to assume that, being comparable the execution time of each proof and constant the room conditions for all the replications, also the temperature of the water at the end point is comparable.
• Immerse the first plate. Wash it using the sponge and making circular movements on all surface. Execute 6 circular complete movements on front surface, then turn the plate and make other 3 movements on the back.
• Remove the washed plate from the bowl, let it drain and pass to the next plate.
• Continue washing plates till reaching the end-point – (image 2) . The end-point is reached when the first permanent break in the foam layer covering the surface of the washing solution is.
  During the execution of the replications defined the temperature and the relative humidity of the room have to be constant, in the range between 18 and 28 °C and 30 and 75% of relative humidity. Values outside this range should be indicated in the report.
• Carry out at least 5 replications of the test for each sample.

7. Results Evaluation
The results for each sample is expressed as the n° of plates washed for each replication or as the amount of soil removed for each replication obtained by multiplying by 5 the number of plates washed in each replication (5 are the amount of soil for each dish in grams).

If required, the estimation of the uncertainty is communicated after having rounded the value to the higher entire number.

If a comparison is required, a product is considered superior to another one when positive results are obtained in at least 80 % of the test rounds.
As an alternative, it is always possible to use statistical methods and demonstrate with a one-sided 95 % confidence range that the test product is as good as or better than the other one.

8. Use of the reference detergent
It is possible to consider as reference for this test a detergent formulation composed as indicated in table n° 2 of the annex.

For checking the good assessment of the whole testing system, the reproducibility of the trained operator, the good occurred preparation of the soil and, in general, for having a comparison, within a long period, with a fixed formulation, it is possible to made in laboratory the indicated formulation (table 2) and using this for carrying out the test in the same condition of a common commercial product.

The standard formulation, used in the measure of 3g in 3 litres of water, gives an indicative value of 13 plates washed +/- 1.

9. Report
Report should contain:
method reference, number, year of publication and revision;
samples reference;
samples dosage;
water hardness and starting temperature;
kind of soil used;
results: n° of plates washed for each replication or amount of soil removed for each replication obtained by multiplying by 5 the number of plates washed in each replication (5 are the amount of soil for each dish in grams);
any other comments or data elaboration.

CONCLUSIONS
On the base of the results of ring-tests performed by laboratories of participating companies, the method proved to be easily reproducible, and sufficiently precise to allow the correct discrimination between different hand dishwashing products. Furthermore it is easy to perform and the required ingredients are easy to find and more appropriate for the Italian market.

Another interesting result of the activity required for the development of the method was the collaboration amongst participating laboratories, that was found very useful to improve and standardize the operations.

Table 1. Composition of THE soil.

Image 1. Example of the sponge.

Image 2. The end-point: the first permanent break in the foam layer covering the surface of the washing solution.

Table 2. Composition of THE STANDARD REFERENCE PRODUCT.

The reference formulation have to respect the following chemical/physical parameters

• clear aspect;
• pH (product as is): 6.0 -7.0.

For more, the formulation is to be prepared: 

• with no perfume and colour;
• with preservative;
• with no thickener.