Warp standards for micro boards and S-warp

August 25, 2016

Rick asks,

I am seeking written accepted warp standards for corrugated. I’m looking primarily for standards on C, B and E flutes.

I seem to recall 1/4″ per running foot as acceptable for B and C.

1. Is the same true for E Flute and other “micro”
2. Is there anything for “S” warp, as that seems to be issue with lower profile flutes.

I have not been able to locate “written” warp standards for E flute and finer corrugated board. And S warp is just a matter of compound warp in both the MD and CD directions.

Yes, the Fibre Box Handbook recommends that warp of corrugated board should not exceed 1/4” (6mm) over 12 lineal inches (305mm) of the material’s surface. However, there does not seem to be anything specifically relating to micro or finer flute board. I would think due to the nature of material and its uses that the warp standards would be different than that of larger flute board.

One has to look to setting standards on paper moisture variations, glue application rates, and corrugator process controls. It’s these input variables that a paper buyer, corrugator supervisor, and control system need to establish. Without getting the front end communicated there is not much chance of flat board.

Hey followers… We’re always open to your input. Please share your knowledge and experience on this subject with us.

— Ralph

Corrugated Safety Data Sheets

August 19, 2016

Kim asks,

Recently a customer asked us to provide a Safety Data Sheet (SDS) for corrugated sheets. Have you ever heard this request before and do you know if anyone has a standard SDS or a template for and SDS?

Yes Kim, it’s a more common request than you might think. Click here for a Corrugated Safety Data Sheet example provided by the FBA. This should help you craft your SDS.
— Ralph

Ideal Starch Viscosity for Corrugated

June 30, 2016

Khuram asks,

I have a few queries regarding corrugated glue.

  • What should be the ideal viscosity and %age solids range for corrugated glue adhesive?
  • Which one is the standard cup to measure viscosity of corrugated glue?
  • As viscosity changes with temperature so can you provide any graph showing change in viscosity of corrugated glue with temperature?
  • As in summer season temperature is higher so viscosity will be less. Is it advisable to control viscosity by adding borax in summer season?


We reached out to Roman Skuratowicz at Ingredion for some expert insight to Khuram’s question. Here’s Roman’s response.

  • Ideal viscosity varies by machine, BHS typically likes 40-50s Stein Hall viscosity, others may like something between 30-40. Most machines overall will run between 30-60 seconds Stein Hall. Fresh adhesive is better than storage adhesive. Using adhesive within hours is preferred but if needed adhesive can be stored overnight or for days with proper formulation, agitation and temperature control.
  • The Stein Hall cup is the standard measure for starch viscosity, although there are European versions as well as the US version. I have only ever worked with the US version, which can be purchased from https://www.gardco.com/pages/viscosity/vi/steinhall_cup.cfm  or  http://www.ringwoodstarchmix.com/ among other places.
  • Correct, viscosity changes with temperature. Follow this link for a temperature/viscosity reference table “Temperature – Viscosity Correction Table (For Stein Hall Viscosity)”. This table is approximate but provides a good guide.
  • First adjustment for viscosity is typically to add or remove a few pounds of starch in the primary. Adjusting borax changes the chemistry of the adhesive and does not impact viscosity as effectively as primary starch. You can also adjust shear time in the primary or borax mix which will impact viscosity. That said, reducing water temperatures is important as you want to keep adhesive storage temperature below 105F, otherwise you will see viscosity growth in storage. Controlling temperatures on the corrugator is also important, as high paper temperatures will flash water from the adhesive and result in brittle, crystallized bonds.

Revisiting Metal Detection in Paper – updated

June 30, 2016

Mario asks –

I read your post on ASK RAPLH about detecting metal in corrugated. Did you find some solution to detect metals in the corrugated plants? We have had issues that have damaged relationships with some of our customers in the food industry.

I would appreciate your comments.

Update – Click here or scroll down

I just returned from my summer meeting with my technical peers that are members of TAPPI. This was one of the subjects we discussed.

One paper mill system with three 100% recycled fibre machines runs samples from every fourth reel, but has never detected metal from its scanners.

You will need to buy a scanner the same as your customer. You will need to calibrate it according to their sensitivity levels. Make sure you can track the order from the receiving of the sheets from sheet supplier, through your converting equipment/process and all the way to delivery of the finished product to your customers. Once you find the source of the metal and your sheet supplier. Once you identify the source of the metal contamination, then you can address the issue.

If you haven’t read the comments from Bill and Clayton regarding detecting metal please click on this link and scroll down the page. Both gentlemen offer some very good insight based on in-plant experience.

Check with your customer to see what kind of detection system they are using and if the same or similar system may be available to meet your needs.

Dick Lund – RC Lund Consulting.

Metal in paper is usually from virgin paper mills – sloughing off of metal in the machines or poorer fiber cleaning than is used in recycled mills.  Recycled mills are specifically designed to remove metal and other contaminents, virgin – not as well equipped.  Further, testing boxes on line in a box plant may be possible but it is very expense and difficult to execute.  Better to get metal free paper!