From finding the right Test Pieces for your site to extending their lifespan, this guide covers everything you need to know about this essential tool for validating your metal detectors.

Metal Detectors can help food production sites to prevent product tampering, reduce the risk of foreign body contamination, improve food safety, safeguard brand reputation, and protect customers. By avoiding spoiled product or even recalls, sites can also drive efficiency and reduce costs. However, none of this would be possible if the Metal Detectors in question are faulty – unable to detect metal contaminants and leaving your operatives with a false sense of security. This is where Metal Detectable Test Pieces prove invaluable.

By running certified test pieces through your metal detector, you can ascertain if the machine is functioning properly. If it is, the test piece should trigger your detector, rejecting the product pack containing the test piece before it moves any further through your production line.

With the consequences of foreign body contamination so severe, it is no surprise that most sites test their metal detectors at the start and end of each run, and will carry out further tests whenever production switches over to a new product. It is also recommended to use test pieces at three points – the front, middle, and end of the batch that is moving through your detector.

But, which test pieces are suited to your operation and how do you extend their lifespan?

We will be answering these questions and more in the following guide, covering everything you need to know about Metal Detectable Test Pieces and their role at your site.

BRCGS Requirements - Clause

"Metal detector testing procedures shall, at a minimum include:
  • Use of test pieces incorporating a sphere of metal of a known diameter selected on the basis of risk. The test pieces shall be marked with the size and type of the test material contained.
  • Tests will be carried out using separate test pieces containing ferrous metal, stainless steel, and typically non-ferrous metal, unless the product is within a foil container where a ferrous-only test may be applicable."

First, let’s take a closer look at the guidance included in Version 9 of the BRCGS Global Food Safety Standard. Here, the Standard emphasises the importance of checking your metal detectors – using test pieces that have been selected following a thorough risk assessment. Your auditor will expect to see a clear correlation between the risks at your site and the test pieces you have decided to use. Otherwise, your testing will be deemed insufficient. We will be covering the process of finding the right test piece later in this article.

The second stipulation is that sites use a combination of ferrous, non-ferrous, and stainless steel test pieces. Here, it’s important to note that sites testing products within foil containers, for example, could be a possible exception, as in this case a ferrous-only test piece will be required. If we use the example of foil containers, this is because aluminium is a non-ferrous metal that would trigger a standard detector. In contrast, a ferrous-specific detector will pass over the aluminium, only triggered by ferrous metals such as cast iron, steel, and steel alloys.

What type of contaminant do I need?

The material of your test piece will be determined by the type of metal your detector is capable of identifying. As outlined in Clause of the BRCGS Standard, this will be dependant on whether or not your product/packaging contains any metal.

If it doesn’t, you will require a metal detector that is capable of detecting ferrous and non-ferrous metals, along with stainless steel. However, if your product/packaging does include a metal, e.g. a ready meal in an aluminium container, you will need a metal-specific detector and test pieces to reflect this.

Below, we have explored three of the most popular contaminants. However, here at Klipspringer, we also supply: 304 Stainless Steel, Aluminum, Phosphor Bronze, Soda Lime Glass, Crystal glass, Ceramic, Teflon, and Nylon.


Ferrous-specific metal detectors detect both ferrous metals and magnetic stainless steel. Examples of ferrous metals include:

  • Cast Iron
  • Steel
  • Steel alloys

If your site is using a ferrous-specific metal detector, it’s important that you are using test pieces from this range, as your detector is not going to be triggered by a non-ferrous option.


Examples of non-ferrous metals include:

  • Copper
  • Brass
  • Aluminium
  • Lead

As previously mentioned, aluminium is a popular choice for product packaging, so non-ferrous test pieces are typically reserved for sites that don’t have any approved metals moving through their production line.

Stainless Steel

It is likely that stainless steel will have been flagged as a possible metal contaminant in your HACCP plan. This is because it is often used as a material for production equipment such as:

  • Scrapers & Spatulas
  • Knives

Due to its non-magnetic properties, a stainless steel test piece is difficult to detect. This is why auditors like to see it included in your testing.

What are the available sizes?

The size of your test piece will be determined by the sensitivity of your metal detector, with this determined by the ‘background signal’ generated by your product. Dry products such as pasta and biscuits produce an extremely low background signal when they pass through a detector, whereas wet products such as dairy and ready meals generate a much higher signal.

As you can imagine a product with a strong background signal will require a less sensitive detector, otherwise the metal detector would be triggered constantly. In contrast, a product with a weak background signal will be able to pass through a more sensitive detector without setting it off.

The size of your test piece will need to sit at the lowest limit of your metal detector’s sensitivity, as this will allow you to validate the detector’s ability to pick up on a foreign body of that size.

In our range of Ferrous, Non-Ferrous, and Stainless Steel test pieces, the following sizes are held in stock for same day despatch:

0.5mm, 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm,    15mm, 20mm.

The Ferrous Test Pieces are also available for same day despatch in sizes 1.6mm and 8.5mm, the Non-Ferrous Test Pieces in sizes 2.8mm and 6.35mm, and the Stainless Steel Test Pieces in 8.5mm.

These sizes are also possible for the other contaminants, but are not held in stock for same day despatch.

As for our extended range of contaminants (304 Stainless Steel, Aluminum, Phosphor Bronze, Soda Lime Glass, Crystal glass, Ceramic, Teflon, and Nylon), we can supply them in any size. The only difference is that they are not available for same day despatch.

Are there any bespoke shapes & sizes available?

Although test wands are the most popular test piece, they are by no means the only option available. Other examples include:

  • Test Sleeves: typically used in conjunction with product trays
  • Test Paddles and T-Bars: typically used for bottles and jars
  • Test Discs: typically used for packaged products or products moving in bulk
  • Test Cards: typically used for bagged products or products moving in bulk
  • Test Wands: typically used for products on a conveyor belt
  • Test Torpedos: typically used for products that undergo a free fall
  • Test Cubes: typically used for products moving in bulk

When it comes to metal detection within the food industry, it’s not always as simple as running a standard test piece through your machine. There are a wide variety of factors that could influence the detectability of metals, such as the orientation and shape of the foreign body. That is why you need to make sure your test pieces are reflective of the unique risks to your operation.

Extending the lifespan of your Test Pieces

One of the most common queries we receive relating to Metal Detectable Test Pieces is: how to extend their lifespan? From conveyor belts filled with items moving in bulk to products that undergo a significant free fall, it is common for test pieces to be exposed to regular wear and tear.

It is no surprise then that so many sites prioritise durability. After all, a chipped or damaged test piece could become a serious point of non-conformity.

What are the most durable Test Pieces?

Although all test pieces offer a certain amount of resilience, selecting the correct shape and size for your specific application is an easy way to improve the chances of them standing the test of time.

You should also pay close attention to the housing of your test piece, in particular the material it has been made from. For example, we supply a range of ferrous, non-ferrous, and stainless steel test pieces that have been made from shatter resistant PTFE – offering additional protection from chips and scratches.

How do I store my Test Pieces?

Even if you select the perfect test pieces for your site – opting for a design that offers optimum durability – you will still need to consider the way in which they are being stored. All too often equipment is damaged due to improper storage conditions, so it’s important to get this right. One solution is a customised Critical Control Point Station with a set storage area for your test pieces. This will ensure your test pieces are easily accessible, but will also lower the risk of them going missing or being exposed to unnecessary damage.

Keeping your test pieces in plain site will also make it easier for you to identify any signs of degradation, giving you the opportunity to put preventative measures in place and encourage accountability amongst your operatives. Click here to learn more about our wide range of storage solutions.

What are the key training points for my team?

Any site that uses a metal detector needs to pay close attention to its culture. Far too often operatives view metal detection as the ultimate safeguard and an excuse for a lack of vigilance elsewhere.

To avoid this, you need to highlight the importance of ‘prevention before detection’, an ethos that will encourage your site staff to reduce the risk of foreign body contamination at every point of the production process.

You can also secure the engagement of your operatives by emphasising the fact that thorough testing will save time and effort in the long run. After all, running a test sample through a detector is a lot less involved than dealing with contaminated products or a recall. Your site staff will also need to take proper care of the test pieces. The storage solution mentioned above will help with this. You should also consider Visual Management solutions to remind your team of the correct way to use the test pieces i.e. where they should be placed, how they should be positioned, and how they should be cleaned after use.

So that brings us to the end of our guide to using and caring for the Metal Detectable Test Pieces at your factory. As you work through your list of priorities and weigh up the different options available, the Klipspringer team would be happy to help.

From providing the necessary certification to helping you to evaluate the sensitivity of your detectors, we can provide support at every level. You can contact us on 01473 461800 or Alternatively, you can use the form below to arrange a free consultation.  

If you would like further guidance relating to the advice shared in this article, the Klipspringer team would be happy to help. Share your details below to arrange a free consultation.