My MCBTM2 dipslide isn't showing any growth but did in previous tests, what might be causing this?

Firstly, it could be that the implementation of good practices has improved the health of your sample and that the low / no levels shown on the dipslide are due to this. It's important to note that no growth on the metal cutting fluid dipslide doesn't mean that your sample has no micro-organisms in it. Levels could still be at up to 100 cfu / ml but standard dipslides aren't sensitive enough for readings below this level. Most samples will not need to meet target levels below 100 cfu/ml so your sample will most likely pass regulations but it doesn't mean that there is no bacteria present.

Each batch of dipslides undergoes testing and quality control before being released for sale. A Certificate of analysis is available for each batch to show the results of this testing and that each batch produced performed as expected. A Certificate of Analysis can be emailed to customers upon request.

If you are still unsure as to what might be causing a change in your results, please see below for factors that can affect bacterial growth.

Correct fluid parameters - are pH levels, fluid concentration and operating temperatures at recommended levels? Were they not previously within their suggested parameters? pH, fluid concentration and operating temperature can all affect bacteria levels. If any of these were previously out of range and now they are where they should be, this would most likely reduce bacteria levels and may explain the change in results.

Storage temperatures – ideally dipslides should be stored between 8 - 15 degrees C. If they are stored at too high a temperature or close to a heat source (such as a radiator), the dipslides will begin to dry out and will not perform as expected. If you are having trouble keeping the dipslides within the recommended storage temperatures, we recommend either storing in a dark, cool place (close to the ground) or using a drinks chiller that has an adjustable temperature function.

Dipslide shelf life – when purchasing our dipslides, the current batch's shelf life can be viewed on the product page under the ‘Buy now' button. The expiry date can also be seen on your dipslide box when you receive it. If you use dipslides after their expiry date, they are not guaranteed to work correctly as the agar on the paddles will lose moisture over time and it will become difficult for bacteria to adhere to and grow on the dipslide.

Incubation temperatures / times – Each type of dipslide has a recommended incubation temperature and time. It is important that these recommendations are followed. An incubator provides a constant, stable temperature and recommended incubation conditions are based on each type of microbe's specific requirements for growth. If you are not using an incubator or incubating at incorrect temperatures or times, this would affect the amount of microbial growth on the dipslide.

A change of metal cutting fluids / treatments – different brands and types of MWF have varying manufacturer recommendations for pH and adjustment factors for refractometer readings. If you have recently changed your MWF, make sure you are following these new guidelines. Aside from this, MWF formulations can differ in their resistance to microbial growth. Treatments and additives can also vary in their effectiveness in inhibiting bacteria and fungi. If you have recently changed either your MWF or additives, this may explain the difference in your dipslide readings.

Testing different areas of a machine
If you are getting very different results to previous tests, is this because you've tested a different part of the machine to usual? It is best practice to always test a sample from the same area of the machine every time so that you can monitor the differences from week to week.

We hope that this list helps you to diagnose what could be causing the difference in your readings.

A dipslide is a simple test that is composed of a plastic paddle and nutrients / agar ('food' for the microbes). If bacteria are present in the sample and they are provided with the correct environment (heat via incubation), they will grow. Very little can go wrong with this testing method if the dipslides have been stored correctly and have not been used past their expiry date.

If you still have further questions regarding your MCBTM2 dipslide or our metal cutting test kits, please contact us via email here: https://dip-slides.com/contact-us