Archive for the ‘Paper’ Category

Checking Moisture of Corrugated Sheets

January 31, 2018

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

Decoding Customer’s Specs

January 3, 2018

Richard asks,

I was a given a spec for an RSC with the paper spec’d as:

K7K 230g + 140g + 230g Kraft C/F.

I don’t know how to interpret this. I’ve reached out to our board suppliers, but I thought you may be able to shed some light. I’m assuming this is a standard way to spec board in some other part of the world.

The paperweight is the easiest to decode. To convert the paper weights from grams to #/MSF simply divide the values by 4.88 and round accordingly to match the closest available weight.


  • 230g = 47.13
  • 140g = 28.68

The other parts of the specification may be a code that is specific to the customers operation. The K7K probably denotes Kraft over Kraft liners and not test liner. The 7 is the caliper, 7mm or .177”. The ‘Kraft C/F’ probably denotes Kraft Corrugated Fluting.

However, that’s a lot of ‘probablies’. To be on the safe side I would try to get the customer to confirm the K7K and the C/F.

– Ralph

Dual Arch Medium

December 1, 2017

Bruce asks,

I am searching for a company that manufactures corrugated sheets with dual arch medium capability. Our location is Dalton Ohio, is there anybody you could refer me to please? I know there is a supplier in Florida that does this medium, but freight is too costly.

I have reached out to some industry contacts. I’m awaiting a phone call. Also a search within the iDirectory revealed no information.

While we’re waiting to hear back, let’s toss this one out the readers too! Is anybody near Ohio running double arch?

— Ralph

What the #1W?!

December 1, 2017

Steve asks,

I have a customer asking me to interpret and explain this call out “ 200E #1W”.

The 200E part is easy. It’s the #1W is a bit more ambiguous…I don’t believe it is industry standard expression. Could it be a designation for coated SBS?

Oh yes. A long history here.

# 1 could be Kemi, Coated SBS, or Coated label stock

#2 does not exist anymore or a lightly coated white top or uncoated SBS

#3 is what we refer to today as uncoated white top.

— Ralph