Irreversible Thermometers: Challenging to Make but Proven Results

    Posted by Jason Romine on April 24,2018


    This blog was formerly titled "The Challenge of Making Irreversible Thermometers"... But we felt a new spin may make things a bit more interesting for our readers!

    American Thermal Instruments has been designing and manufacturing irreversible ascending thermal indicators for many years. These indicators change from white to color (red or black) when temperature rises above their designed threshold, and the color change is permanent. The technology is well-established and is used in pharmaceutical, medical, industrial, and food applications where high temperatures can cause products to spoil, as well as in manufacturing processes where certain temperatures must be reached to produce a quality product.

    Visible Color Change

    ATI’s’ irreversible ascending technologies use the melting of a carefully selected phase change material (PCM) and carefully chosen dye to indicate whether a label has exceeded a customer’s chosen temperature. To make a label, these materials are dispersed into a liquid carrier to form an ink, then the ink applied to paper or film by one of several printing methods. When the label exceeds its designed temperature, the dried ink deposit melts, producing a visible color change.

    The challenges come in when selecting the right PCM. Our experts have determined what type of PCM is needed based on the temperature threshold requested. Finding a PCM that is both safe and accurate is critical to ensure a positive customer experience. The process to turn this PCM into an ink includes grinding the material into a small powder and adding thickeners and emulsifiers to get the right texture for printing.

    While there are a number of critical steps behind the scenes, the technology is quite simple for the user. The labels can be applied at the product, box or pallet level. At the applied level, the indicator will activate once the temperature threshold is met and provide a simple, visual indication that quality may be affected. With a ±1°C accuracy, you will know if the product may need to be reviewed for safety or efficacy, or if the shipment should be deemed compromised.

    We have experienced a lot of success stories with our irreversible thermometers Here are some industries and use cases you should consider for irreversible thermometers:

    Pour test image

    Medical Device

    Many global Medical Device manufacturers specify they have met regulation by adding an irreversible thermometer at the product-level. Some devices like heart stents, hearing aids and laboratory kits, may be considered unusable or unsafe if it reaches the specified temperatures.  By placing an indicator at the product-level, they have the flexibility to sort and review each box of product rather than recalling an entire shipment.


    Our industrial customers certainly have a wide range of applications for high temperature irreversible thermometers. Whether it’s a car engine that is being tracked for warranty abuse or a transformer that may overheat due to exceeded temperatures, irreversible thermometers can provide an easy visual for quality checks. With a range of up to 230°C, high temperature applications are still valid with this cost-effective measure.


    While most of us hear about cold chain or CRT (controlled room temperature) as critical paths for pharmaceutical drugs, there are a number of personalized biologics now being manufactured that have very low or high temperature ranges they must maintain. Validated packaging along with an irreversible thermometer has been a fitting solution for a number of our pharmaceutical customers. This ensures the drug moves from manufacturing to the last mile and stays safe and effective.

    Whether you have one temperature that is highly critical for your product to maintain or a range of temperatures that could affect your product, high temperature irreversible thermometers are a cost-effective and easy-to-use solution. Custom thermometers can be created for a number of industries and applications.




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    Topics: Industry/Chemical, Chemical Monitor, Temperature Monitoring, irreversible thermometers, Industry Knowledge

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