Archive for the ‘Corrugating’ Category

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

Laminator Glue Recipe

December 1, 2017

David asks,

I have just installed a Flute laminator Mounting machine here in UK that I purchased from China. While I was there they said that most of the machines in China would be using Starch Glue. I wanted to try some so they sent me about 25kg of the components to try with the idea of buying from China if it works. However there are problems with importing it, so I have started to look at buying materials here.

We are either mounting uncoated paper to Test corrugated board or to Unlined grey-board our speeds are not much more than 70 metre/min max but much lower for most jobs around 45mtrs/min

The recipe from China is as below. The problem is that they are saying the Calcium Carbonate has other additives in it. I guess they want me to buy from them and won’t say what those additives are nor are the instructions to prepare the glue very clear.

The recipe I have is as follows

  • 5kg Corn Starch
  • 5kg Calcium Carbonate + whatever there may be in it
  • 16kg water
  • 300gm Caustic soda
  • 150 gm Borax

I was told to mix the starch and the calcium carbonate and then add the Caustic soda and Borax.

My question is:

Does the above recipe look viable? I think it’s possible that the calcium compound is just with that nothing added. I have seen recipes for starch glue including all of the other contents and I have also seen that the Calcium can be a filler which might make it more viscous?

The cost of all of these chemicals is much cheaper than the PVA based adhesives we have available here and I understand that Starch glue has been used in corrugated for many years.

If you are able to advise if this recipe will work or if there is a different combination of chemicals it would be very helpful.

PVA adhesives are recommended for laminating because their elastic properties reduce the extent of score cracking. Yes they are more expensive, but the finished product is typically of a much higher quality.

I do believe that the calcium carbonate is nothing more than a filler and increases the viscosity of the mixture.

I have copied some of my network contacts here in the States for their expertise.

Let’s also toss this out to our readers and see what their experiences have been.

– Ralph

Peeling white liner issue

October 24, 2017

Khuram asks,

We are experiencing a peel off issue with white 135gsm test liner. This issue is random and the top layer of white liner gets peeled off in the cross direction during conversion. (See the picture below for examples.) We have our own vertically integrated board mill which is providing this white test liner and as far as ply bond strength is concerned we have tested it different lots (using method TAPPI-569) and its average values are >250J/m2.

This issue can have several root causes.

One is that the ink is too tacky and it is pulling the white fibre from the brown base sheet.  It can also be that the ink is drying on the printing plate or otherwise not releasing properly from the plate.

Second is that there could be a poor bond between the white fibre top sheet and the brown base sheet.  This is usually caused by poor fibre developing during the pulping process.  It could also be an issue of poor water drainage in the board making segment.  There could be a contaminated water system, or there may not have been enough starch between the two layers to hold them together.

Sometimes closure tapes can be used in the box plant to predict the ply separation.

So there are a few things that you can look at. Let’s toss this out to our followers and see what they have experienced and information they can offer.

— Ralph