What to Watch for in Cold Chain Packaging Performance Graphs
Performance charts and graphs can be helpful in evaluating insulation technologies for cold chain packaging, but some are much more useful than others, and some are outright misleading. You really need to look at the data carefully. Here are some things to watch out for when looking at performance data.
1. "It's No Comparison"
Some charts just show how one type of insulation helps keep things cold. The problem is that even a plastic bag will keep things cold if you stuff it with enough ice, so this kind of chart may not tell you much. As an example, the chart here is taken from a foil bubble bag brochure we found online. The chart is labeled, "Temperature Comparison". It's supposed to show how well the foil bubble bag helps keep the contents cool.
Without knowing more about the contents of the box and the amount of coolant, it's impossible to say how well the insulation is working. At our lab, we tested a foil bubble bag alongside a thick plastic bag and found little difference between the two. In this case, the fact that the temperature inside the box so closely follows the outside temperature suggests that it's not insulating very well.
2. "On Thin Ice"
Measuring how well a box insulates ice is a straightforward way to measure performance. In fact, it's our favorite method, at least for initial comparison testing. But this method works only if you measure how much ice actually melts. The graph to the right is a good example of how not to use ice for testing.
The chart, taken from a competitive web site, is supposed to show that Box 1 and Box 2 have equivalent performance, because the ice in each box - or rather the ice / water mix - stays at 32 degrees F. The problem is that you have no idea how much of the ice has actually melted, because the entire ice / water mixture within each box will stay at 32 degrees F until all the ice has melted. One box might be 95% ice / 5% water and the other box 5% ice / 95% water, but the temperature in both will be 32 degrees F.
The simple fix to this problem is to open each box at the end of the test and measure how much ice is left in each one. We actually recommend this method to those wanting to compare our boxes to competitive products.
3. "Now That’s Just Cheating"
Our last example is probably the most obvious example of twisted data. In this case, it is claimed that Box 1 performs better because it keeps the contents cooler than Box 2. No mention is made of the fact that Box 2 starts at a much warmer temperature and actually heats up at a slower rate than Box 1.
Box 1 actually gained heat (lost cold) at a much faster rate than Box 2. Box 2 was fairly steady and flat, showing a slower and more gradual heat gain. But they would have you believe that Box 1 insulated better because it finished the experiment at a slightly colder temperature, which is easy to do if it starts off 10 degrees colder.