Checking Moisture of Corrugated Sheets

Tim asks,

Recently we encountered corrugated sheets with dry liners and medium that created problems converting. Is there a way for us to test sheets for moisture content at our facility? If so, is there a listing of the ranges?

Moisture meters, or moisture analyzers, can be used to test the moisture content of corrugate sheets. There are a number of portable, hand-held models available. (Most look surprisingly like a taser) They are rather inexpensive (ranging from $50 to $600) and a modest range of testers with varying capabilities and features are available in this range. These units provide instant readings of paper moisture content and should meet your needs. If you purchase a meter/analyzer make sure it is suitable for measuring paper. Some of the least expensive models are only for wood or hard materials. Also check the accuracy rating of the device. If it has a .01% or .02% for paper it should do fine. The same devices may have a 1% – 3% accuracy for wood, but that won’t affect testing paper.

6 to 8 percent moisture is the sweet spot for corrugated paperboard. Below 6% and the risk of cracking scores will increase, perhaps significantly depending on the paper. If the moisture content goes above 8% you will start to see a decrease in compression strength. Reports indicate compression strength can decrease as much as 6.5% per every 1% of moisture over 8%.

Now, in your case (simple checking for machineability) moisture meters/analyzers should work fine. However, they are not the most accurate method for checking paperboard moisture. Should you ever need to certify board for food or pharmaceuticals you may want to find a testing facility that can provide results via the oven method.

– Ralph

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