Testing Blue Ice Packs

A baseline. The water in this cooler will be the same for all tests. It simulates the food that needs to be cooled.

To start, we first measured the cooling power of ice. It had to be the same volume and nearly the same weight as a Blue Ice pack. In fairness, we tested "Freez Pak: The Iceberg," a generic ice pack and not the genuine Rubbermaid Blue Ice.

First we filled a cooler to an amount which will lead to the cooler being full after we add the "Freez Pak." We used a computer-friendly sensor to measure the temperature. The cooler was a simple lunch pack cooler from Coleman that many people use to take their lunches to work.

As you can see, the ice pack took up less than 25% of the total volume, so we needed quite a bit of water in there. For each test, we started with the water at room temperature. This allowed the test to last a shorter time than if we had started with cold water. However, since both the ice and "The Iceberg" pack had to cool the same amount of water, the test was fair

Ice Cube Test. We will use ice cubes to cool the water in the cooler.

The first test involved using bare ice cubes. They were placed in the cooler and as you can see, the cooler was completely full after the ice was added.

The lid was closed, and the temperature was recorded.

Ice in a bottle test. The Blue Ice Is contained in a bottle of sorts. It is fair to compare ice in a container to a blue ice pack.

For the frozen bottle test, we used the same amount of ice, but within a bottle similar in volume to the blue ice pack.

The surface area of the bottle was much smaller than the area of all the small ice cubes.

By measuring the temperature curves for two extreme cases (a bottle roughly in a cube) and many small ice cubes, we were able to combine this data to get the curves for any amount of surface area in between a square bottle and lots of ice cubes. Since "The Iceberg" has a more surface area than the bottle, we picked 40% of the way between the frozen cube bottle and the small ice cubes for our comparison.

Temperature versus time curves for water ice.

Here are the resulting curves for the water ice. Notice that the only differences between them are during the first five hours. Once all the ice is melted, it didn't really matter what the surface area was.

Blue Ice pack test. Only Blue Ice used to cool the water in the cooler.

The final result. We place a Blue Ice pack in the same amount of room temperature water as before, and measured the temperature response.

The Blue Ice cooled to a lower temperature and for a longer time than regular water ice. In this case about 3 hours longer than regular ice, but with different amounts of food or different ratios of ice to food, you could expect different results, but clearly "The Iceberg" significantly out-performs regular ice.

Using simple ice cubes did cause more cooling effect during the first two hours than the "Freez Pak," but then after the ice melted, the temperature quickly rose above the "Freez pak" temperature. We were frankly surprised with this result because we did not expect the latent heat capacity of this gel to be significantly better than water.

What is FreezPak The Iceberg?

The gel is probably about 70% water, 25% propylene glycol and 5% hydroxypropyl methylcellulose. It is the last ingredient that turns it into a gel. Propylene glycol is typically used as an antifreeze in recreational vehicles. For a 25% propylene glycol, 75% water mixture, the freezing point is about 15 degrees Fahrenheit.

We are basing this on he assumption that is is quite similar to Blue Ice

Other related products to Freez pak: The Iceberg

Rubbermaid Blue Ice Blocks

This product consists of a blue gel inside a hard plastic container. It was clearly the prototype for the Freez Pak product. Due to the rigidity of the plastic container, this product is not as flexible in conforming to the food in your cooler. The gel probably contains 70% water, 25% propylene glycol (judging by the MSDS for the product) and probably 5 percent by weight hydroxypropyl methylcellulose. There is also a trace amount of blue dye. The contents are based on US Patent US 4462224 A. Although propylene glycol in trace amounts is considered non-toxic, swallowing the gel is considered potentially dangerous. It should be pointed out that some people have serious allergies to propylene glycol.

Flexifreeze Ice Sheets

This product consists of an array of plastic pockets pre-filled with water. The shipping weight makes the product fairly expensive for what you get. Sheets come as large as 15" x 19" but can be cut to the size needed.

Rubbermaid Blue Ice Sheets

These are similar to Flexifreeze, but are pre-filled with the blue ice gel. They generally come in smaller size sheets.

TechniIce

This product is similar to Flexifreeze, except that the pockets are not pre-filled. Instead, you soak the pack in water until it absorbs water into the cells. Once in, it generally stays in. In fact, the cells continue to absorb water, so you have to protect them from water, lest they overfill and pop.

Thermafreeze

This product is similar to TechniIce. The sheets are shipped dry and require hydration before using. Users report better quality control with ThermaFreeze and that it is less expensive than TechniIce.