Denise asks,
Do you have a graph or chart that shows how moisture in paper affects its durability and strength? For example, how much moisture does board start off with from the Corrugator? If you store a corrugated sheet in a cooler or if it sits outside in hot humid weather, how much can moisture increase in the board? Does increase amounts of moisture in board effect the durability and strength of the board?
It would be very helpful to me if I had access to a chart or graph that I could show to my customer on how humidity, moisture and temperature change effects the durability of corrugated products.
You may want to check the FBA handbook. George Maltenfort’s book Corrugated Shipping Containers: An Engineering Approach (ISBN-13: 978-0961630218) contains some excellent charts and tables on compression strength vs. moisture content. Unfortunately, this book is out of print, but if you can locate a copy it may be very useful.
Corrugated board stabilizes at 7 percent moisture at an environment of 72 degrees Fahrenheit and 50% relative humidity. Above and below these conditions board takes on and gives off moisture. Recycled and Kraft components react differently. The upper limit on moisture content is 20 percent.
There are very mobile and portable scientific instruments to measure moisture content (MC). There are many multipliers used to factor compression based on initial performance at the beginning of the life cycle/supply chain. However, generally the rule of thumb is that increases in moisture causes board to lose strength.
If anyone out there knows of a good source for George’s book please pass the information along.
—Ralph
askralph 
October 5, 2015 at 6:54 pm
Thanks Ralph,
Great to see you and Sharron in Ft.Worth. very cool town.
Thanks for sharing this.
One more question, I had a “cheat sheet” on a table converting linerboard into Grams, like they use else where in the WORLD, and I have misplaced it.
Do you have one you could send me? All of the “on line calculators” are asking for sizes….ie IP Basis Weight Calculator…but this doesn’t look right to me.
Thx
Tyler
Tyler W. Howland
VP of Business Development
Sound Packaging L.L.C.
480-940-2010 Office
480-220-5001 Cell
October 7, 2015 at 10:58 am
To convert lbs/msf to g/m2 multiply by 4.8828.
example: 35 lbs/msf = 171 g/m2
October 7, 2015 at 11:25 am
The problem with those charts and graphs that show the loss of BCT at different moisture levels is that they’re so simplistic. Studies were conducted with a 200 mullen construction in C-flute at a steady temperature and constant humidity (no fluctuations). Back in the day, it was not a terrible point of reference because 200 mullen accounted for 40% of the volume in a typical box-plant. Many people were quick to adopt these multiplying factors, including CAPE and TOPS in their palletization software.
The problem is that the % loss in BCT for a 29 ECT construction with recycled liners won’t be nearly the same as a 275 mullen with virgin liners. Dave Carlson also makes the good point that there’s a +/- 22% range in BCT for boxes in a standard (72 deg F and 50% RH) environment so imagine what the range would be at higher and/or fluctuating humidity and temperatures.
Unfortunately, I think environmental testing is the only way to get a reliable number. Even then, those numbers have to be trended. To gain an understanding of both temperature and humidity, you’d have to test in 3 environments: standard, tropical, and freezer. I’m not aware of anyone who’s shared a study like that.
March 6, 2018 at 8:33 pm
Corrugated boxes are crackling within hours of manufacturing in hot n humid atmospheric conditions,how to avoid such situations.
March 7, 2018 at 9:40 am
Jugal –
This is a question that has been asked many times on Ask Ralph and a complex one as there are many variables that lead to cracking scores. The paper the environment, the equipment the design and the tooling all can have an effect on the scores. If you search “scores” or “cracking” on Ask Ralph you should be able to find some very helpful information.