Corrugated Box – The Master Guide - PakFactory Blog

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When you think of cardboard, you might assume it is just one type of packaging material. However, there is more to it than that. Cardboard is one type of material, and corrugated cardboard is another. Both materials are often confused with one another but serve different purposes depending on the product.

Source: PakFactory

In this post, we will explore the differences between cardboard and corrugated cardboard, go in-depth into the various aspects of corrugated material, look into quality control, and discuss the benefits and uses of such material. By the end of this article, we hope to give you a better understanding of corrugated boards so you can make the best decision for your product’s packaging!

Corrugated Definition

Before we begin, let us define what a corrugated box is. Simply put, these boxes are made from sheets of corrugated cardboard, a prevalent shipping option for its protection and durability. In fact, 95% of all shipped products in North America use corrugated material! But what is corrugated cardboard?

Corrugated cardboard, or corrugated fiberboard, is a sturdy packaging material typically made from three layers of kraft paper. The outer layers are called liner boards, and the wavy layer is called flute. Adding additional layers for protection is also possible with corrugated, which we will discuss in more detail later.

Corrugated vs. Cardboard – What’s the Difference?

Now that you know what corrugated packaging is and how common it is in shipping, you may wonder what the difference is between corrugated and cardboard. We’ve mentioned briefly that corrugated cardboard differs from cardboard, but let us unpack this topic further.

Corrugated Cardboard

Cardboard is generally made of thick paper stock or heavy paper pulp. It’s typically used in folded cartons for smaller product packaging but can also be used as structural support inside a box to keep its shape during transit. However, cardboard by itself is not very protective.

Corrugated, on the other hand, is different. It has three fiberboard layers, offering increased durability,  protection, and versatility. This box material is among the best options whether your company is shipping large packages or sending a few products. Still unsure of the difference? Check out the chart below for a comparison!

  Rigid Boxes Folded Carton Boxes Corrugated Boxes Set up None if not foldable Needed Needed Sturdiness High Low High Product Safety High High with the aid of inserts High Cost Generally High Depends on printing & finish Depends on printing & finish Appeal Generally High Depends on printing & finish Depends on printing & finish Reusable Yes Usually not Yes

Corrugated Construction – Paper Liners and Flute Grades

With a better understanding of corrugated materials, it should be less daunting now to take an even closer look at the types of corrugated options available, starting with the kinds of paper liners.

Kraft paper liners consist of 70-80% “virgin” chemical pulp fiber, which results in a top paper grade that is very stiff and durable. Kraft paper is the most sustainable option out of all the types of paper available, but it is also the most costly.

Source: PakFactory

Test paper liners are less expensive than Kraft because they use more recycled fiber content, resulting in less durability. The higher recycled fiber content also makes the paper more difficult to print on, but it is very common to use test paper as the inner liner board of a corrugated box.

The last paper option is flute paper, available in Semi-Chem and Waste Based Fluting. Semi-Chem uses virgin fibers and a neutral sulphite semi-chemical process, while Waste Based Fluting uses 100% recycled fibers.

But speaking of flute paper, now is a good segue into the different flute grades available, too!

Corrugated Flute Grades

Corrugated flute is similar to liner boards save for the construction.

Corrugated flute provides cushioning, strength, and compression-resistant qualities to your package depending on the different grades, allowing for even more customization with your packaging. But before we examine each flute grade in detail, look at our corrugated flute chart for a quick visual comparison:

Source: PakFactory

A-Flute – 1/4” is the first type of corrugated flute. This flute grade has the highest protection and cushion qualities. It is very good at handling compression and stacking and is often used for packaging fragile items.

B-Flute – 1/8”. This flute appears much thinner than others but is still quite strong, with excellent puncture and crush resistance. B-flute has outstanding all-around performance for various packaging or as additional material for padding and dividing. It even has a flatter surface for higher-quality printing and easy die-cutting. 

C-Flute – 3/16” is flexible and one of the corrugated boxes’ most versatile flute grades. It has average crush resistance, stacking strength, and printing properties. You have likely seen C-Flute used for shipping boxes but also for packaging glass, dairy, and furniture products.

E-Flute – 1/16” is not typically used for shipping. E-flute thickness is on the thinner side of flute grades, so it is often used as an alternative for paperboard folding cartons. However, you may still use E-Flute for cosmetics, fragile glass, ceramics, and other small and delicate products. E-Flute has excellent compression strength, crush resistance, and a relatively flat surface for high-quality printing applications.

F-Flute – 1/32” has protective qualities similar to E-Flute but with an even smoother surface for high-quality printing. It is common for you to use F-Flute for clamshell packaging in the US fast-food industry, but in Europe, this grade of corrugated fluting is a standard option for specialty and retail packaging.

Corrugated Cardboard Thickness and Style

Now that we’ve covered the different types of paper liners and flute grades, it’s time to look at thickness! Below is a summary of the standard thickness options available:

Liner Board – The ‘face’ of the fiberboard sheet. You glue the flute onto this board.

Single Face – Consists of one liner board with glued flute visible on one side.

Single Wall – The most common thickness. Two liner boards with fluted fiberboard glued in between.

Double Wall – Three sheets of liner board and two fluted fiberboards in between.

Triple Wall – Four sheets of liner board and three fluted fiberboards in between. This option can withstand heavier weights up to almost 300 lbs but is less flexible.

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Examining a little further with double and triple walls, different combinations of flute grades are possible with these options. Some industry standard combinations include:

AC Flute – A mix of the two most protective corrugated grades. AC Flute is excellent if you need extra protection for harsh shipping and handling processes. 

BC Flute – An outstanding all-around performer, this combination provides high-level transit protection and is common for shipping boxes.

EB Flute – Provides superior transit strength and safety, while the outer E-Flute allows for an excellent, high-quality printing surface.

Box Styles

With everything from construction to thickness covered, the style of boxes is the last topic to cover before moving on to quality control. By combining layers, customizing flute grades, or adding interior padding, corrugated boxes can fit any packaging need. 

Custom corrugated boxes meet any specific requirement of the user, but below are some common styles for corrugated packages:

Source: PakFactory

Quality Control Tests

With the sheer amount of design and customization options available at your fingertips, there might be many questions about protection. Corrugated boxes are subject to stress and impact during packing, shipping, and storage, so there needs to be ways to test your custom package’s strength.

Some standard tests include the Edge Crush, Flat Crush, and the Burst Test.

The Edge Crush Test is one of the essential tests for corrugated packaging. As the name implies, force is applied perpendicular to the edge of the corrugated board until it buckles. The results ensure the strength and durability required to handle heavy loads and stack resistance.  

The Flat Crush Test is also used and is similar to the Edge Crush Test. Force is applied directly on the surface area of the corrugated fiberboard until the flute flattens and compromises its structure. This test similarly determines the compression and stacking resistance of the corrugated board required to carry heavy loads.

The Burst Test, or the Mullen Test, challenges the durability of the corrugated fiberboard’s surface by determining the force needed to puncture the board.

All of these tests ensure the quality of custom corrugated packaging so your products have the highest level of safety they need to reach their final destination.

Source: PakFactory

Box Maker’s Certificate

After customizing and thorough testing, the corrugated box is ready for its box maker’s certificate, or BMC! The BMC is a convenient and efficient way of describing some quick specifications about the box, and there are two versions: the Ect-rated BMC and the Mullen-rated BMC.

You will notice a few differences, but these certificates provide the same information:

1. The Box Manufacturer on the outer ring indicates the company responsible for manufacturing your box.
2. Board Construction is the information displayed directly under where it says box certificate. This information tells whether the box is a single, double, or triple wall.
3. Minimum Combined Weight Facings is the total weight of the liner board used before the entire liner board is cut and made into boxes.
4. Size Limit is the maximum outer dimensions of the box. This section is helpful to know for storage and shipping purposes.
5. Gross Weight Limit is the maximum weight allowed for the box and the items within.
6. City and State are located at the bottom of the label. It indicates the location where the box is constructed and shipped.

Benefits of Corrugated Packaging

If you’ve followed along until now, you may already understand some of the benefits of corrugated packaging. Corrugated cardboard and corrugated boxes have seen enduring popularity because of the many benefits they have to offer.

Some of the main reasons for their popularity include:

1. Protection and Durability – Corrugated boxes are one of the best packaging options for those seeking to protect their items during transit. It can handle the impacts of being moved around and shipped, and the cushioning offers much support. These boxes can withstand harsh impacts without damaging products and are an excellent barrier to the elements, making them best for e-commerce packaging.
2. Environmentally friendly –  Sustainability has become increasingly important, especially for packaging. Corrugated boxes use recycled fibers, making them a better contender for sustainable packaging alternatives.
3. Customizable – Because of the many options available for raw materials and their environmental-friendliness, corrugated packaging is the best option for those looking for bespoke packaging, including printing. The shape and thickness are easily customizable alongside graphics and surface printing.

But Are Custom Corrugated Boxes Right for You?

Many industries benefit from using corrugated packaging, especially e-commerce. Depending on the size and shape of the packaging, shipping and mailing can be more manageable. However, there are still some drawbacks to this type of packaging.

For starters, corrugated boxes are susceptible to inclement weather, such as rain or snow. The packaging can become deformed or lose its shape.

But the biggest drawback of using corrugated cardboard is its cost. Compared to other options, corrugated is on the higher side of the price range, which may be disheartening for companies with a lower budget. However, many ways exist to reduce costs and create affordable luxury packaging!

Source: PakFactory

Get Started – Choose a Corrugated Box!

Corrugated packaging offers many benefits, particularly in its durability and customizability. With this material, you can have a lot of creative freedom in designing the packaging precisely as you wish while ensuring your product is safe during transport.

If you want to learn more, contact one of our packaging specialists today to begin your next project with corrugated packaging!

Understanding Shipping Box Strength

When you ship your products, you must ensure that they remain safe. No matter how much you trust your shipping partner, you never know what might happen on the road, and you need to trust that your shipping box will protect your products so that they will arrive to your customers intact.

On the other hand, you also want to ensure your packaging is economical. Stronger boxes are heavier and, therefore, more expensive to ship, and they use more materials, which costs more and is less environmentally friendly. You should find that sweet spot between protection and practicality when choosing your boxes.

As packaging experts, we know the ins and outs of shipping box strength and how to choose the perfect box for your products. Here’s our guide.

How is cardboard strength measured?

The strength of the shipping box sheet is described with a number and letter (e.g., 23B or 23ECT B). The number notes the Edge Crush Test (ECT) rating, which describes how much weight a single sheet can withstand if standing on its edge. The letter describes the tightness of the waves of the corrugate, otherwise known as the fluting.

What is an edge crush test (ECT)?

Corrugated strength is most commonly described using ECT. It tells you how much weight a corrugated sheet can withstand when standing up on its edge in a lab setting. For example, a 23A corrugated sheet can withstand 23 pounds of pressure, as can 23B, 23C, and 23E.

Another common way to note corrugated box strength is with The Mullen Test. This test measures how much pressure (in PSI) a corrugated sheet can withstand when horizontally suspended in the air. While this method is relevant for specific applications, ECT works well for most small carrier shipping boxes. ECT is also the only strength measurement applicable to boxes made with recycled content.

ECT determines whether a box is strong enough for its contents. Heavier products will need boxes with a higher ECT. However, you must consider more than just the ECT. The size and type of box you choose will also play a part. For example, a 32C box can carry more weight than a 32E box because it’s thicker.

Check out this reference from UPS, which has delivered millions of packages just like yours. UPS does not address 23B, so we have added our guidelines based on our experience.

Maximum Weight of Box and Contents (lbs/kg) Size Limit of Box Length, Width, and Depth Added (inches/cm)* Minimum Bursting Test (lbs per sq. inch/kg per sq. cm) Minimum Edge Crush Test (ECT) (lbs per inch/kg per cm width) 5-10* 30* 125 * 23* 30 75 200 32 40 75 200 40 50 85 250 44 65 95 275 55 80 105 350 N/A

*EcoEnclose recommendations; not provided by UPS.

What are flutes?

Flutes are the s-shaped, wavy paper between the linerboard of a corrugated sheet. It gives corrugated boxes their strength and resistance to bending and pressure. Flutes vary by their height and how tightly or loosely they are waved.

Below are standard flute sizes from thickest to thinnest.

• A Flute: 36 flutes per foot and 1/4" thick. While it works great for shock absorption, strength, and cushioning, it exceeds the needs of small carrier shipping. Not offered by EcoEnclose.

• C Flute: 39 - 43 flutes per foot and 11/64” thick. This is the go-to flute for standard box styles (RSCs and FPFs).

• B Flute: 42 - 50 flutes per foot and 1/8" thick. It’s designed to resist crushing and is good for folding, making it an excellent selection for TL and LM boxes.

• E Flute: 94 flutes per foot and 1/16” thick. The thinnest of the shipping-appropriate flutes, it makes an excellent printing surface and has a nice overall presentation.

• F Flute: 125 flutes per foot and 1/32” thick. It’s inappropriate for shipping or eCommerce, but it can be interesting for certain primary packaging applications. Not offered by EcoEnclose.

For added strength, corrugated sheets can also be double- or triple-wall. eCommerce shipping boxes are generally made with single-wall B, C, or E flutes, all striking an appropriate balance of strength and lightness.

Why shipping box strength is important

Cardboard strength ratings are essential to understand the type of box you need fully. Once you know the specs of your shipping box strength for your products, you can easily order the boxes you need.

In terms of optics, choosing the proper shipping box strength will not only protect your items but also show your customers that you care. A high-quality box can often denote high-quality products and services to your customers. However, respecting your customers by keeping shipping costs low is essential. Thicker, heavier boxes might portray high quality, but they’ll cost more to ship. The shipping box strength you choose must protect your products, display quality, and minimize costs; it’s a delicate balance that can sometimes be difficult to find.

If you’re having trouble determining which shipping box strength measurements you need, contact us or order free samples to see which packaging suits your eCommerce business.

Learn more: The Ultimate Guide to Custom Shipping Boxes

Which corrugated material should I use?

When deciding which shipping box durability is best for your business and products, there are a few things to consider. It goes beyond ETC and fluting. You’ll need to consider box style, cost efficiency, and more to determine which custom shipping box best fits your brand.

Box style

For a presentation-style box (such as a Tab Locking Box or Literature Mailer), you will probably want to select a board that’s easy to fold, such as a B or E flute. While we make presentation boxes with thicker material, the folding and creasing may be a little more cumbersome. We typically suggest 32 ECT C or 44 ECT for RSC boxes, depending on the weight of the product shipped. We can make most custom shipping boxes from most boards, but we suggest ordering a sample first.

Protecting your product

If you’re shipping small, light items that are not fragile, you likely don’t need the heavy-duty box. However, you’ll likely need something a little sturdier if you're shipping fragile items. When determining which box will best support your product, consider the following.

• Can your product be bent?
• Is the product heavy, and could it potentially break through the box?
• Will it need extra padding during transit?
• Does it need protection from punctures or other potential hazards?

Answering these questions will help you narrow down your packaging offerings.

Printing

Some corrugated sheets, especially 32 ECT E, are thinner and sleeker, resulting in more successful printing. Conversely, the 44 ECT has fewer flutes that are twice as wide and create small ridges on the printing surface. Such ridges make it difficult to get an even print finish. Therefore, if the aesthetics of the box are essential to your brand, consider tighter fluting.

Cost efficiency

Consider the box cost, the inbound shipping (to your fulfillment location), and the outbound shipping (to your customer). Stronger board material usually has more cardboard material per square inch. This is going to cost more.

EcoEnclose's Corrugated Sheet Strengths

EcoEnclose offers five different corrugated sheet options: 23ECT B Flute, 32ECT B Flute, 32ECT C Flute, 32ECT E Flute, and 44ECT C Flute. We work with these five options because we have found these satisfy nearly all non-industrial shipping needs and are the most cost-effective options to meet said needs. As you consider your options, here’s a handy chart to determine the best sheet type for your box.

Sheet Box Style* Definition Use If: Avoid If: 23 ECT B Flute LM, TL, OPF, Tray Economy: 1/8" thick. Our lightest weight and least expensive board that uses minimal source material. More subject to crushing as it is not as strong or as stiff as other options. You ship items that collectively weigh less than 5lbs, want to minimize costs or want a basic print on the outside of the box. You ship heavy items (>15lbs), have a large box (greater than 32 inches of L + W + H), and want to print on the inside of the box. 32 ECT B Flute RSC, LM, TL, FPF, OPF Standard: 1/8" thick. Its higher ECT rating gives it more strength and rigidity than 23B and provides more cushion and shock resistance than 32E. You ship items that collectively weigh between 15lbs and 25lbs. 32 ECT C Flute Large LM, Large TL, RSC, FPF, OPF, Tray Strength & Cushion: 11/64” thick. One of our two thickest options, providing even more cushioning. You ship items that collectively weigh 15-25lbs or have a larger tab locking box or literature mailer greater than 30 inches in L+W+H. You ship very light or small materials. B flute can be 15-20% cheaper than C Flute. 32 ECT E Flute LM, TL Design: 1/16” thick. Thinner and more aesthetically pleasing than 23B and 32B. Same ECT rating as 32B, but is more subject to bowing and offers less cushioning. You ship items that collectively weigh 15-25 lbs. You want a very clean design, an excellent printing finish or to print on the inside of the box. Ideal for limited storage space because the material is thinner than B or C flute. You ship very light or small materials. Raw material on 23 ECT can cost 15-20% less than that of 32 ECT. 44 ECT C Flute RSC, FPF High Strength: 11/64” thick. Our thickest option is heavy-duty and our most expensive board. You ship items that collectively weigh up to 40lbs or you have a high-value product that needs the heavy-duty crush protection. You ship very light or small materials. Raw material on 44 ECT can cost 40-50% more than that of 32 ECT.

*EcoEnclose recommendations; not provided by UPS.

Our three most popular shipping box strengths are 32E, 32B, 23B. Notices the differences in thickness, and the faint lines in 23B.

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