Robert Kaminski of Supply Source One educates readers to the content and structure of boxes used for packing, shipping, moving and self-storage needs.

February 21, 2009

7 Min Read
Choosing the Best Retail Boxes to Sell in Self-Storage

Have you ever bought something because it was cheaper and seemed “close enough” to what you really wanted, only to find out when you used it that the quality was much less than what you had hoped? There’s nothing like finding out firsthand the meaning of the saying: “You get what you pay for.”

Not long ago, a client noticed that the corrugated boxes ordered from a local box vender were very light in color and felt pretty flimsy, too. We sent the boxes for testing, which confirmed the recycled paper content was way too high, and glue coverage was downright skimpy. In fact, though they had the required “Manufacturer’s Certification Stamp” printed on every box, these boxes failed the test every time. In other words, though the client was paying a fair market price, he was getting a very unfair deal—inferior boxes.

Do you know how your own boxes really stack up? One simple test: When you see a stack of boxes leaning to one side, it’s most likely because the bottom boxes are being crushed. And that is a real-world failure to meet the edge crush test.

If this happens in one of your tenants’ units, you risk much more than crushed edges. What if the boxes you sold your customer topple over, damaging valuables or injuring the customer? That’s the problem with substandard “bargain” boxes.

Since so much can ride on the quality of the corrugated boxes you sell to your customers, you need to learn how to get what you pay for. Once you know how high-grade corrugated cardboard is made, you’ll understand why cheaper boxes are almost always inferior.

There are two key areas you’ll need to know if you expect to bargain with box vendors from a position of strength: construction and stock. Caution: Though the following is a bit technical, take the time to read it. It’ll make you a smarter box buyer.

Corrugated Construction

The strength of a box is in its design and construction. A corrugated sheet consists of two major components: the linerboard and the medium. Linerboard is the flat paper that covers both sides of the corrugated sheet; the medium is the “fluted” or arched paper found in between both liners.

It takes the right kind of glue, applied hot for the right length of time, to weld the three components together. If the fluted paper isn’t properly bonded between the two linerboards with a starched-based adhesive, it can weaken the strength of a corrugated sheet. How that fluted paper is shaped and how well it is glued in place determines how well it resists bending and pressure from all directions.

When the flutes are arranged on their ends, they form columns that can support a great deal of weight. There are five commonly used flute shapes. Each has its pluses and minuses. In moving boxes, the most commonly used is the “C-flute.” Though there are other designs, because the C-flute “waves” or “ripples” are taller than others, they have greater stacking strength, making them the better choice for storage situations.

Box strength is measured by two accepted industry tests: The Mullen Test measures the bursting strength of the corrugated, while the Edge Crush Test (ECT) measures stacking strength. A 200-pound Mullen box and the 32 ECT box would have comparable stacking strength, but they serve vastly different purposes.

The Mullen Test box, better suited for the protection of heavier contents, is popular for heavy-duty industrial shipping applications. On the other hand, the 32-pound ECT box was designed for those who need stacking strength. They are lighter in weight with the good stacking characteristics so important to those of us in the self-storage industry. Though a Mullen Test box would be stronger in every way, it’s a lot more expensive than a high quality ECT box. That is why 32 ECT boxes are the gold standard in self-storage.

The stock (or paper) that is used is as important as how a corrugated sheet is made. The amount of virgin pulp fibers and the length of those fibers in a corrugated stock add substantially to box strength. Though everyone supports recycling, in this case, more than 20 percent recycled content results in a weaker box.

Putting It All Together

Overall, box strength is determined by the combination of the flute shape, the quality of the paper used, plus the amount and type of adhesive and whether it is given time to adhere properly.

How do you know if everything has been done correctly? One way to be sure the material of the box you’re purchasing meets industry standards is to look for the Manufacturer’s Certification Stamp. Flip the box over. The stamp is usually printed on one of the bottom flaps.

Aside from giving the name of the maker, the stamp identifies the material as “single wall,” and is supposed to certify that it meets the ECT of 32 pounds per inch. Of course, the box mentioned at the beginning of this article had the stamp printed on it but clearly didn’t meet the declared standards. What then?

And this is where the games begin. To reach a 32 ECT, box makers can use many various combinations of paper and tolerances to meet or get close to the posted rating. Taking one or all of the following shortcuts usually gets a box maker to a lower selling price in the market.

Recycled paper. Remember, recycled paper is cheaper than virgin pulp but not as strong. The higher the recycled content, the weaker the corrugated. Reputable manufacturers use 80 percent or more virgin pulp fibers.

Manufacturing. Joining together the three pieces (those two linerboards and the medium) means using the best quality, mildew-resistant, starch-based hot glue applied at a high enough temperature and allowed enough time to stick. Since time is money, in order to lower their costs, some manufacturers will speed up the process, skimp on glue and play fast and loose with proper glue heat levels.

Dimensions. One new client was surprised to learn that the “small” boxes they had been sold were not the industry standard 1.5 cubic feet in size but an odd-sized 1.3 cubic feet. The slightly lower price they paid was for slightly smaller boxes. That meant that the glass and dish packing kits they were selling wouldn’t fit because the kits were designed to be set in standard-sized 1.5 cubic feet boxes.

Fudging on any one of these three, or any combination of them, is how some box suppliers can afford to sell at a lower price and still make a good profit.

Ways to Box Back

How can you protect your interests and those of your customers? First, don’t be afraid to ask for an independent test of the quality of product you’re buying. No reputable supplier would refuse.

Also, beware of small specialized vendors. Look for a supplier who sells more than just boxes. If your other business is riding on it, they would be foolish to risk it by selling you second-rate boxes. Plus, if the price seems too good to be true, it probably is. Finally, don’t focus on price alone. You don’t compete in your market on rental price alone do you?

Keep in mind that your customers can always get used, discarded, bargain-basement or otherwise crumby boxes anywhere. When you’re telling them that your boxes are worth a few cents more because only quality corrugated boxes can adequately protect their possessions, remember this line: You get what you pay for. It’s almost always true.

Rob Kaminski is vice president and general manager of Supply Source One, a division of Schwarz Supply Source, which has been a national retail supplier for more than 100 years. With 14 warehouses across the country, the company offers the self-storage industry a complete selection of retail products as well as office, maintenance and janitorial supplies. For more information, visit

Subscribe to Our Weekly Newsletter
ISS is the most comprehensive source for self-storage news, feature stories, videos and more.

You May Also Like