Serrated Knives

Published July 1, 2016. From Cook's Illustrated.

Overview:

Some people call them bread knives, but we think serrated knives are more versatile than that. We use them to cut everything from crusty baguettes and buttery brioche to tender cakes and squishy tomatoes. We last tested serrated knives in 2008; with new options on the market, we decided it was time to revisit the category. We selected nine serrated knives, priced from $19.99 to $199.99, and ran them through a series of tests to find one capable of handling all our usual tasks. We focused on knives with blades around 10 inches long—in past tests, shorter blades couldn’t cut through wide loaves or split cake layers horizontally, while longer blades simply got in the way. We included the all-around winner and the Best Buy from our 2008 testing in our new lineup and started slicing.

To find the best, we worked our way through 50 pounds of tomatoes, 18 yellow cakes, nine loaves of challah, 30 crusty rustic loaves, and nine towering BLT sandwiches loaded with extra fillings. Multiple testers, with varying dominant hands, hand sizes,… read more

Some people call them bread knives, but we think serrated knives are more versatile than that. We use them to cut everything from crusty baguettes and buttery brioche to tender cakes and squishy tomatoes. We last tested serrated knives in 2008; with new options on the market, we decided it was time to revisit the category. We selected nine serrated knives, priced from $19.99 to $199.99, and ran them through a series of tests to find one capable of handling all our usual tasks. We focused on knives with blades around 10 inches long—in past tests, shorter blades couldn’t cut through wide loaves or split cake layers horizontally, while longer blades simply got in the way. We included the all-around winner and the Best Buy from our 2008 testing in our new lineup and started slicing.

To find the best, we worked our way through 50 pounds of tomatoes, 18 yellow cakes, nine loaves of challah, 30 crusty rustic loaves, and nine towering BLT sandwiches loaded with extra fillings. Multiple testers, with varying dominant hands, hand sizes, and skill levels, assessed the knives and rated them on their cutting ability and comfort. We also evaluated how well the knives retained their edges throughout testing.

Here’s the news: If you hate slicing bread because it makes you think of sawing or struggling, it’s probably your knife’s fault—we were shocked by how bad some of the knives were. Brand-new blades turned glossy loaves of challah into shaggy piles that looked as if they’d been run through a blender. Others were so uncomfortable to use or so terrible at slicing that testers begged to quit halfway through their loaves. But others were a pleasure to use. The best glided through the crustiest of loaves with minimal effort, leaving behind even, tidy slices. Why were some great while others failed so spectacularly?

What’s the Point?

The point (pun intended) of using a serrated blade instead of a straight-edge blade (like that of a standard chef’s knife) is the serrated blade’s ability to bite into foods that are too hard or squishy for straight knives to get a purchase on. The points sink into the food while the scooped-out gullies between them reduce the blade’s friction as it moves through the food. Less friction makes it easier for the user to saw back and forth and cut through the food cleanly.

We examined the serration patterns of our nine knives and found two distinct styles. The first, which we noticed on two of the knives, didn’t have any points. Instead, the serrations were scalloped or rounded. This style is purportedly designed to dull more slowly and to create more cutting angles for more effective slicing, the theory being that by rounding the serration, more of it will hit the food at the point of contact. But we found just the opposite: Knives with rounded serrations struggled.

Those with the classic serration style of pointed tips were, in general, much more successful. But there were some exceptions. What made the difference? After counting and measuring the serrations along all nine blades, we landed on a surprising discovery. The best knives had broad, deep, pointed serrations and, most interestingly, fewer of them. Our top-ranked knife had 29 serrations compared with the 55 on our bottom-ranked blade. The idea seemed counterintuitive, so we turned to Sarah Hainsworth, knife expert and professor of materials and forensic engineering at the University of Leicester, to help us understand why the number and shape of serrations matter.

Hainsworth explained that when a user pushes down on a serrated knife, the force exerted is divided among the serrations. The more serrations there are, the less power each one gets. Conversely, the fewer the serrations, the more power each serration gets. This is why we observed blades with fewer serrations biting into food much more readily than those with more serrations.

Next, we zoomed in and looked at the shape of each individual serration. Deeper serrations with pointier tips are better at biting into food than rounded or shallow serrations because the force is also spread over the surface area of each tip. So the same force distribution theory applies: A narrower tip will have more force concentrated behind it and will thus have more power to bite into food.

Angling for the Win

Since we last tested serrated knives, we noticed that manufacturers are now following the same trend we’ve seen in chef’s knives: They’re making the blades narrower. Narrower blades, sharpened to 16 degrees or fewer (from the very tip of the serrations to the top of the bevel running along the entire edge of the blade) excelled, while those sharpened to 20 degrees or more felt dull. When cutting, you’re essentially pushing one object through another object. The narrower the object that you’re pushing (i.e., the cutting implement), the less force is required. For a knife, less required force means the knife feels sharper to the user. The notable exceptions to this trend were the two knives with rounded serrations; they had narrow edges, but their serrations were so dull that it didn’t matter. And while some blades were curved and others straight and some blade tips were rounded while others were pointed, we found that neither aspect had an impact on the knives’ performance.

The knives’ handles also affected their rankings. Testers preferred handles made of grippy, rather than smooth, material because they felt more secure. Good handles also had what ergonomists call “affordance,” meaning they allowed multiple comfortable grip options. Cutting is a complex task: Usually we hold the knife vertically, but sometimes we want to hold it horizontally (such as when dividing cake layers); sometimes we want to pinch the spine of the blade to maximize our control, but other times we want to use a “power grip” (much like the grip you use when shaking hands), which requires grasping farther back on the handle.

In addition to a grippy handle with several comfortable holding options, our winning knife also had an exceptional blade that was sharp out of the box and, unlike some knives in our lineup, stayed sharp, cutting wafer-thin slices throughout our testing. The best part? The knife costs just $22. A mainstay of culinary schools, the Mercer Culinary Millennia 10" Wide Bread Knife aced every test we threw its way, earning its spot as our new top-rated serrated blade.

Methodology:

We tested nine knives ranging from 9.5 to 10.25 inches in length and from $19.99 to $199.99 in price. Multiple testers, with varying dominant hands, hand sizes, and skill levels, assessed each knife. We weighed and measured the knives and counted and measured their serrations; blade angle and handle material were reported by manufacturers.

CUTTING: We rated each knife on how well it halved cake layers widthwise and sliced through tomatoes, bread (soft and crusty), and loaded BLT sandwiches. Points were awarded for crisp, tidy cuts that required minimal effort.

COMFORT: We evaluated the ergonomics, grippiness, length, and weight of each knife; those that were comfortable and secure rated highest.

EDGE RETENTION: We used each knife to slice squishy, tactile tomatoes at the beginning and end of testing; those that started and stayed sharp rated highest.

AVERAGE SERRATION WIDTH AND DEPTH: We pressed each knife’s nonbeveled side into Silly Putty, measured three serrations on each knife with calipers, and calculated an average for each knife.

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