WHEN IS MY RAZOR BLADE SHARP?

Razor blades and straight razors have a very high sharpness compared to other cutting tools, such as household knives. As a geometric quantity, the sharpness of an edge is the width of the cutting edge caused by the manufacturing process. Even under the finest honing conditions, micro-abrasions of the cutting edge material produce a stump that deviates geometrically from the theoretically possible geometry of a line, the theoretical sharpness. The razor blade is ground extremely narrowly and has a very acute cutting edge angle. In addition, razor blades are usually coated with a lubricant that contributes to a comfortable shave. In conjunction with the manufacturing process, a geometrically particularly sharp cutting edge is produced. This sharpness is also evident in use. Compared to household knives, the razor blade or straight razor requires considerably less force to cut through an identical cutting material.

The PWFT has proven this with objective test methods that determine the sharpness of razor blades and razors on the basis of quantifiable characteristic values.

The simplest, but also most subjective test is to shave. With the shave, you determine the "perceived sharpness", which reflects your own subjective assessment of the shaving process. Your assessment depends on many factors, including your subjective feeling, but also on the texture and length of the beard or body hair and the shaving foam used.

As a rule, shavers have two criteria for shaving and sharpness evaluation. Firstly, the separation process of the hairs during shaving is evaluated. The perceived sharpness is expressed in particular in the fact that the hairs are separated without pain. This is the case when the razor blade exerts little or no pulling force on the hair root when separating the hairs. The prerequisite for this is that the hairs are separated with little force. The perceived criterion of a "smooth shave" is therefore well suited for subjectively determining sharpness. A second criterion is the result of the shave. If the skin feels smooth after shaving and the hair above the skin has been removed as closely as possible, the shave has been satisfactory. With both criteria together, you evaluate the quality of the razor, which is after all usually used as a multi-blade system. However, you do not use them to assess the sharpness of the blade, as the perceived shaving experience is determined by many other influences. The PWFT has developed test methods that can be used to determine objective and quantifiable sharpness parameters for razor blades and straight razors. These are independent of subjective perception and enable a comparison of different shaving systems.

We have developed sharpness testing methods with which the sharpness of a razor blade can be determined on the basis of a characteristic value.

If you search the internet, you will find numerous suggestions for testing the sharpness of knives and blades, especially in blogs. Often mentioned is the paper test, in which a sheet of newsprint or copy paper is held with one hand while the other hand guides a blade to make a cut through the freely hanging and otherwise untensioned paper. A blade is considered sharp if the cut can be pulled through the paper with a smooth motion, producing a smooth cut with no tears. Other arrangements, such as the "tomato test" are only suitable for knives. A razor can be run over the hair on your forearm in a scraping cut, or alternatively take the abrasion from the scraping cut of a fingernail as a sharpening criteria. All these methods are very subjective and unsuitable in their resolving power to carry out a comparative assessment of cutting edge sharpness. A quantitative and reproducible measurement result is missing.

The PWFT has developed objective test methods for the sharpness of razor blades and razors with which the sharpness of new and used razors can be comparatively evaluated on the basis of characteristic values.

For the user, a razor is dull when the shaving process becomes uncomfortable or the shaving result is no longer satisfactory. As a rule, the razor is discarded when the shave no longer feels smooth and comfortable or the hair is not completely shaved off. The shave becomes painful if too much traction is exerted on the hair root during the cutting process or if the front tip of the blade shows minor damage.

As the degree of dullness of the razor blade increases, greater cutting forces are needed to cut through a hair and thus the pulling forces also increase. During the use of a razor, the sliding blade coating is first worn away. Similar to cooking pans coated with Teflon (PTFE), this blade coating wears off during use and the shave becomes less comfortable. In the further dulling process, mechanical damage to the blade, as well as skin, hair and soap residue deposits lead to wear and tear of the razor. If this causes a disturbing sensation when shaving, the razor is replaced. If the shaver feels uncomfortable, it will be replaced. However, this sensation is very subjective and depends, for example, on the sensation of pain, the texture, density and thickness of the hair and the condition of the skin. Apart from that, the shaving sensation does not only deteriorate with the wear of the blades. Incorrect or too dry shaving foam plays just as much a role as the length of the hair and the care of the razor. In terms of sensation, a daily shave is more pleasant than shaving a 3-day beard. With multi-blade shaving systems, cleaning the spaces between the blades also plays an important role. If the spaces are clogged, the newly cut hairs has no space to move and the shaving process is impaired. It is almost impossible to determine the degree of dullness of a razor blade with the subjective sensation of a shave. Regardless, it is indisputable that dulling of the blade has a negative impact on the subjective perception of a shave.

PWFT has developed objective test methods for the sharpness of razor blades and razors, with which comparable service life curves for razor blades can be determined from quantitative characteristic values. Learn more (razor test equipment, life curve)

There are different objectives and methods for razor blade quality testing. Manufacturers of multi-blade shaving systems monitor the various stages of the manufacturing process using methods adapted to the respective manufacturing and assembly processes. The quality assurance of the manufacturers ranges from material tests at incoming goods to monitoring of the manufacturing processes to functional tests and optical inspections after assembly of the cartridges. The quality assurance measurements are designed to ensure that no defective products, classified by the customer as not meeting quality standards, reach the market.

PWFT offers quality inspections on the end product and carries these out on behalf of the customer.

In the process, random samples are taken from the delivery quantities for the trade and are tested. In addition to a visual inspection and the measurement of blade position and orientation in the cartridge of the multi-blade razor system, PWFT tests the razor blades for sharpness and durability. If the quality inspection is carried out regularly and is appropriate in scope and method, the PWFT can award a seal of approval.

PWFT is an independent service provider for quality inspections and awards a seal of approval when customers have regular and proper quality inspections carried out by the PWFT and the inspection results are incorporated into the continuous improvement process of their production. The quality tests are carried out in accordance with statistically validated test methods and recognised scientific standards. The quality seal certifies conformity with the test specification and is awarded when the test results meet the specifications.

With our sharpness tests, you can determine the appropriate time for regrinding.