13 Chef’s Knife Models with Varying Sharpness & Hardness – Ceramic Knives Sharp & Durable but Prone to Breakage

15 August 2018
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13 Chef’s Knife Models with Varying Sharpness & Hardness –  Ceramic Knives Sharp & Durable but Prone to Breakage

A chef’s knife, sharp and durable, is an indispensable kitchenware in most households.  In a joint test with the International Consumer Research and Testing (ICRT) on 13 models of multi-purpose chef’s knives, the Consumer Council has found the stainless steel models more variable in sharpness and hardness performance while the ceramic models were even in such performance; indeed fared better than the stainless steel models in durability but they also had one drawback in flexibility – they were more prone to breakage when used with excessive force or accidentally dropped.  Consumers should take note of this.

Covered in the joint test were samples of 13 models of chef’s knives: 10 stainless steel models priced from $188 to $2,480, a 12 times difference; the remainders 3 were ceramic models priced from $219 to $1,299, a difference of fivefold.  The highest overall rating was achieved by 2 highest-priced stainless steel models with a score of 4.5 points, and the rest with relatively lower prices also have good overall performance, scoring 3.5 or 4 points.  According to the results, the 4 cheaper samples ($219 to $378) performed similarly well with 3 samples priced over $1,000.  Take the ceramic chef’s knives as the example, the $219 sample was comparable to the one costed $1,299 with both scoring 4 points.  Consumers will do well to shop around to consider if the product is of value for money. 

The test was conducted mainly with reference to ISO 8442-1 and ISO 8442-5, focusing on the hardness and sharpness of the blade, and durability based on cutting edge retention, anti-corrosion, strength, and the extent of damage following drop tests.  The test also focused on the actual user perspective, engaging trial users to evaluate and rate the samples’ ease of use.

Sharpness is most important in using a chef’s knife.  In the evaluation of their sharpness, the test measured how deep the knives could cut through a pack of paper.  At the samples’ out-of-box condition, the results recorded measurements from 60mm to 111mm deep, all of which were above the minimum standard requirement (50mm).  The 10 stainless steel samples were re-sharpened and put through a second round of test.  7 of the re-sharpened samples were found to have improved their sharpness compared with their out-of-box condition.  The collated results of the 2 tests showed variances in the sharpness performance of stainless steel chef’s knives, with rating ranging from 3 to 4.5 points.  The ceramic samples were relatively better and more even in performance.  But because of the hard material they are made of consumers will generally find it more difficult to be re-sharpened so only the test results of their out-of-box condition were computed giving with 2 of the ceramic samples achieving 5 points and the 1 remainder 4 points.

A knife’s hardness could determine if its cutting edge will stay sharp; a higher hardness could produce a better cutting edge retention, its hardness much depends on factors such as its material and the processing quality. 11 models were found to perform well, scoring 4 points or above.  Among them 5 stainless steel and all the 3 ceramic samples attained the top rating of 5 points.  But 2 others were measured with weaker hardness of a rating of 2 and 3 points respectively.

Durability was assessed by cutting edge retention, anti-corrosion, strength and drop tests in combination.  The cutting edge retention test was to increase the number of cutting of the paper packs in the sharpness test to 60 cycles and measured each cut to calculate the total value for each sample. When conducted on the samples in the condition as received, the results showed the 3 ceramic samples to give equally outstanding performance with total paper cutting depths between 1,248 and 1,359mm, all scoring 5 points.   As for the 10 stainless steel samples their total paper cutting depths were only 145 to 424mm, among them 2 samples were rated with only 2.5 points.  The worst sample was below the standard requirement (150mm), thus rated “poor” by the laboratory.

On anti-corrosion, all samples were immersed in a 60°C salt water solution for 6 hours, and no noticeable corrosion was observed on any of the blades, a most satisfactory performance.  Further, all samples performed well in the strength test, with no deformation after being subjected to a series of extreme temperature change.  In the drop test, 3 ceramic samples were found more serious extent of damage – the blade or handle were broken, or the edge and point of the blade snapped off.  All ceramic samples received a mere 1 point in the drop test.  The stainless steel fared better with 5 samples found slightly damaged, scoring 3 to 4.5 points.

Users are reminded that a blunt knife edge will not only affect its cutting performance but it will also increase the risk of accident when more strength is needed for cutting. Thus, users of stainless steel knives are advised to resharpen them regularly which will help prolong their lifespan and reduce wastage in support of sustainable consumption.

There are different types of sharpening rods or stones and sharpeners available on the market, from under $100 to several thousand dollars.  The former two will require some skill in use but the sharpeners are easier to use.  If necessary, enquire with the agents or knives shops about the offer of re-sharpening services.  Whether ceramic chef’s knives are suitable for re-sharpening depends on the claims of the relevant products.  In fact in 1 of the 3 ceramic test samples was specified “Never resharp” but 1 sample came with a mini reshapening tool with a usage instructions manual.

Consumers using chef’s knives are further reminded to take note of the following:

- Always be careful in the use and storage to minimise the risks of accidents of drop and damage;

- As the edge of the knife is very sharp, store properly in knife sheath or knife block;

- Always use wood or plastic cutting board and not on stainless steel surface, glass top, or porcelain plate;

- Don't use the knife point as a can opener;

- Knives should be cleaned individually by hand instead of dishwasher lest any clashes with other kitchenware;

- Knives should be kept away safely from the reach of children, they should only use knife under adult supervision to avoid accident. 

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