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What happens with the metalworking fluid samples? The journey of the metalworking fluid samples through the laboratory
Triage for customer samples
Our customers from all over the world send metalworking fluid samples to Hasle Rüegsau in Switzerland. Hundreds of customer samples found their way to our laboratory last year, where they were analyzed in detail by our specialists. Almost 7,000 of these samples were sent to the microbiologists in our customer service team. What happens with a customer sample? What is involved in standard analysis and what is the difference between a dip slide and a plater?
Triage for customer metalworking fluid analysis
In the early morning, all the metalworking fluid samples that have arrived from customers all over the world are lined up on the laboratory bench in customer service. Each sample is delivered together with a sampling report. This records the customer name, products used, tank size, filling date and much more. Measurements showing the concentration and the local pH value are also included. Each of these customer samples is now assigned a unique internal number and all the data collected are recorded electronically. The samples that have arrived for standard analysis include the following two used emulsions, which I will now deal with in a little more detail:
Customer sample 1
Customer sample no. 1 / Customer sample from Germany
A German customer uses our B-Cool metalworking fluid. The pH value and the concentration have already been measured on site and our sales representative sent a sample from the 6,000 liter sump to Switzerland for further analysis.
Customer sample no. 2 / Customer sample from Switzerland
A Swiss customer has been using a Blasocut metalworking fluid for several years. In order to check the condition of the emulsion, a sample of the used emulsion was taken from the customer’s central system. Because of their different product properties, the two customer samples now complete different test procedures.
Customer sample 2
CustomerYeast, mold and bacteria cultivated on nutrient agar
Customer sample no. 1 – Analysis of conserved products:

Microbial growth is not usually tolerated in traditional products because the ingredients suppress the growth of microorganisms in the ready-to-use product.

In order to check that everything is in order with the metalworking fluid, we use the so-called dip slide for analysis.

The dip slide is coated on both sides with a nutrient agar. If bacteria, yeast and/or mold are present, they will divide on the dip slide until they grow into a colony that is visible to the eye. This test tells us whether or not there is microbial growth and whether it involves bacteria or fungi

Customer sample no. 2 – Blasocut products:
This product group consists of so-called bio-concept products, in which bactericides are deliberately avoided. The growth of a particular harmless waterborne germ is specifically promoted; this enters the emulsion through the mixing water. The Blasocut products are analyzed using a plater. Here, too, a nutrient agar is used to cultivate the microorganisms. In contrast to the dip slide, differentiated colonies in different colors, shapes and surfaces are allowed to form here. The smell, which can vary greatly depending on the type of colonies, also helps us to assign the microorganisms to the correct genus and species.
The dip slides and platers are incubated at 30 to 35°C – because microorganisms from the metalworking fluid like things to be warm. If present in the metalworking fluid in a viable form, bacteria, yeasts and molds divide within 48 hours and form visible colonies. Using the dip slide for traditional products, we can therefore tell whether the system is stable. With the plater for the bio-concept products, we can identify exactly which bacteria colonize our metalworking fluid after the test.
Evaluation of samples and recommendations for customers

In the case of standard analysis, the evaluation of the samples takes around two to three working days. After we have completed our investigations, customers receive a report that contains all the parameters measured by the various laboratories and advice on whether control measures should be initiated.

Customer sample no. 1 from Germany features an empty dip slide. As no growth was detected on the dip slide, we can now be sure that the metalworking fluid used is stable.

In the case of customer sample no. 2 from Switzerland, a plater was set up and we can see that the organism identified as the primary bacterium is dominant. The characteristic colonies tell us that this bio-concept is also stable.

In my next blog post I will explain the specific analysis methods, such as PCR DNA analysis or the flow cytometry device, for which we have developed a special purification method designed for metalworking fluid samples in particular. These and other analysis methods are only used for certain customer samples and for research purposes and cannot be carried out by every metalworking fluid laboratory.

Production of customer reports on the PC