Keep it on ice…

Shipping frozen products can be a gamble for any shipper, and even the receiver. What is worse than opening a long-anticipated package, to see that it has spoiled or melted? At PeriShip, we assist you in ways to avoid a catastrophe like this. The number one goal of shipping perishable items is to keep the shipping environment cool, keep heat from penetrating the inside of your shipping system for the number of days you are shipping. Here is a secret to help slow down the penetration of warm air in the box: remember the R-value! The R-Value is what keeps heat from penetrating the inside of your container, and a material’s R-value is the measure of its resistance to heat flow- the higher the R-Value, the greater the insulating effectiveness. Take this into consideration when evaluating internal insulation like Styrofoam coolers or Mylar bags.

The next question you may ask is, “what type of coolant do I use in order for my product to stay frozen during transit?” PeriShip understands the needs of one type of food may be completely different from another, and we can make the right recommendations for you. There are two effective options depending on what is being shipped, frozen items or refrigerated items. If you plan to use dry ice, it will offer a longer transit time because of how extremely cold it is (-109.8 degrees Fahrenheit). If you choose to steer clear of dry ice, your other option is using gel packs. However, there is a slight disadvantage to using gel packs; the frozen gels limit transit because they stay frozen for a shorter amount of time. Fear not though, there is also an advantage to using gel packs as well. You can maintain a ready supply of frozen gels in your freezer so they are ready to pack when you are!

Not only should your choice of coolant be accounted for when you are planning on shipping frozen or temperature sensitive items, you should also think about your packages transit times and the “bumps in the road” that may cause delays. In general, whatever your transit time is, you should add six to twelve hours to the total to account for those “bumps”, whether its weather delays, or a package remaining on the recipient’s doorstep until they are home from work, or even the recipient not finding the package until the next day. The way that you pack your shipping system also adds to the total transit time. By following our basic packing tips when shipping your products, you can rest assured knowing that your products will stay at safe, frozen temperatures!

Tips for Shipping Frozen: Dry Ice

  1. Precondition your product beforehand – doing this may only require 24 hours for a small payload and maybe 2-3 days for larger ones.

    Dry ice properly contained in Kraft paper. Dry ice has sublimated from original size.

    Dry ice properly contained in Kraft paper. Dry ice has sublimated from original size.

  2. Precondition shipping system (box and pad sets) – Place system in freezer for 3-4 hours before packing. This will draw out heat, saving 30-35% of product and refrigerant life, which is accounted for as adding transit time.
  • No room in your freezer? No problem! Place 2-3 frozen gels or 1-2 pounds of dry ice inside your system and seal up for 4-5 hours prior to packing.
  1. Ready to pack? Place one half inch of some type of dunnage on the insulation floor of your shipping system. Dunnage is just a type of filler: newspaper, brown Kraft paper, or packing peanuts.
  2. Center your product inside the system (on top of the layer of dunnage).
  3. Place dry ice on top of payload – Why not on the bottom you ask? Cold air filters down and will create its own natural airflow going beneath your payload and then right back up to the top!
  4. Maintaining maximum transit – Use two inch slabs of dry ice vs. pellets or nuggets; it sublimates at a much slower rate in bigger slabs. It is also less of a hazard to the recipient when they open their package.
  5. Sublimation process- This is the phase at which carbon dioxide changes from a solid to gas. Dry ice is frozen carbon dioxide. Due to the sublimation process, you will need to wrap the dry ice in heavy Kraft paper or a brown paper bag so to protect anyone handling the contents of the package.
  6. Got too much empty space? Fill it with dunnage! Make sure to place the dunnage on top of the dry ice, but do not pack it so tightly as to cut off natural inside airflow. When heat begins to penetrate the inside of your shipping system in transit, it goes to the nearest empty space and expands. The increase in mass and strength starts the defrosting process.
  7. Safe sealing – To allow for the safe release of CO2, seal only the middle seam of the box top and bottom, but not the flaps. Sealing the cooler could create a dangerous buildup of the gas.
  8. Finally, you are going to place a number 9 dry ice label outside of the shipping box, and complete the required information as appropriate. These stickers can be ordered at no charge through FedEx, UPS or the US Post Office. You can also call FedEx at 1-800-463-3339 to order.

Tips for Shipping Frozen: Gel Packs

  1. Precondition payload… As described above!
  2. Precondition shipping system… As described above!
  3. Precondition gel packs- To do this, you will need to freeze the gel packs for 24-48 hours prior to shipping. Ideally, you would lay the gel packs as flat as possible in single rows- whatever shape gels are frozen at will be their shape at packing time.
  • The correct placement of gel packs on top of the product will encourage proper cool air flow.

    The correct placement of gel packs on top of the product will encourage proper cool air flow.

    Can I place gels on top of each other? Sure! Just make sure to put a piece of cardboard in between each one because gel packs have a tendency to self-insulate.

  1. Ready to pack? Cut a piece of cardboard the size of your insulation floor and place on top of the insulation floor. This will allow inside airflow to circulate more evenly, as well as serving as a simple heat barrier.
  2. Center your payload inside the system.
  3. Place frozen gels on the top and bottom of the payload. The number and weight of gels used will depend on the size and weight of your payload, along with the number of days you are trying to ship.
  4. Empty space? Don’t forget to use the dunnage as described above! And remember, do not overstuff dunnage so tightly as to cut off natural inside airflow.
  5. Seal all seams. Unlike shipping with dry ice, you will be sealing off the outside flaps of your package with pressure sensitive tape so to trap the cold air inside and to keep the warm air from penetrating in.


And as always, make sure to place a PeriShip sticker on the outside of your package!


One thought on “Keep it on ice…”

  1. Thomas says:

    Its really good. Very informative post. Thanks

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