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Phase change materials, also known as PCMs, change phases at a specific temperature and are often used to keep substances cold but not frozen. For example, if you have a substance that needs to remain at exactly 3°C or below, there is a PCM specifically formulated to meet your needs.

Shipping with Dry and Wet Ice

Every substance changes phase at a specific temperature. We all know that water goes from solid to liquid at 0°C. When a substance reaches its phase change temperature, it absorbs a large amount of heat at an almost constant temperature until the material is melted. This makes ice a good coolant for anything that needs to remain at 0°C or colder, so long as the packaging can handle the liquid water. Solid carbon dioxide, also known as dry ice, changes phase at -78°C and is used to keep substances frozen at -78°C or below. Dry ice has the added advantage of sublimating into a gas, leaving no liquid behind to damage a substance or its packaging. 

Shipping with Phase Change Materials


  • Unlike dry ice or wet ice, PCMs can be refrozen and reused
  • PCMs maintain a very specific temperature range that is often cold, but not frozen
  • PCMs work in both directions keeping your substance from getting too cold or too hot


  • PCMs need to be “pre-conditioned”, which is a very specific process that can take hours to freeze or refrigerate them to the right temperature
  • Adding more PCMs doesn’t linearly add onto the amount of time a package can be shipped/stored. If 4 gel packs are needed to maintain a certain temperature for 3 days while shipping, 8 gel packs would not give you 6 days with the same result
  • Dry ice is readily available and logistically easier for a recipient to ship with versus the time and resources required to re-freeze a PCM


Each shipment is unique and Mercury’s expert team provides a customized solution to meet your specific needs. Contact us to learn more.


Shipping Best Practices