- Razor-blade edge that is not straight due to razor defect
- Rough surfaces on the razor due to defect/damage
- Incorrect blade position in razor head
- Excess pressure of razor on skin
- Excess speed of shaving strokes
- Shaving multiple planes of the face in single strokes
- Shaving in the wrong direction in sensitive-skin areas
- Too many strokes in the same area
- Insufficient prep and lather
- Dull blade
- Mismatched razor design (blade angle, reveal, exposure, gap, and more) to skin sensitivity and hair toughness
- Mismatched combination of blade, razor, and skin
For the purposes of this discussion, blade angle refers to the angle measured along the line of shaving direction, in relation to the razor's top cap and safety bar.
To elaborate on this, if you think of the edge of the top cap, which is a line, and the safety bar, which in a straight-bar DE represents a second line parallel to the edge of the cap, generally speaking these two parallel lines determine the shaving plane of the razor head. The more perpendicular the blade is to this shaving plane (when viewed along the non-cutting edge), the more more harsh the scrape of the blade edge against skin.
|Contrast different (exaggerated) blade angles: |
Left is smaller angle (less harsh), right is
larger angle (more harsh).
So larger blade angle would generally have the blade bent less under the cap and would be closer to the cross stroke on a letter T (when viewed in cross section, that is, from the dull edge of the blade), while a smaller blade angle would require the blade be more curved under the razor's top cap, and could be thought of as looking in cross section like a letter T that has more drooping cross stroke. All other things equal, a small blade angle would be considered less harsh, more slicing, less scraping, of the hair, and a larger blade angle less cutting, more scraping (so therefore might be more irritating to the skin).
|Smaller blade reveal (left) compared to larger (right).|
The safety bar limits the blade contact with the skin. There are different safety-bar designs from nearly round cross section to open comb. Safety bars may have less effect on harshness and more on long-hair cutting ability. Open-comb bars tend to let many longer whiskers better direct access to the blade, and may also allow more lather on the skin while the edge is actually cutting hairs. Scalloped cuts in the safety bar also may allow lather to better cushion the shave, but, like less-grooved safety bars, may press longer whiskers down, away from the blade, making the pass less effective.
|A slant-bar razor not only curves the blade from edge to edge;|
it twists it too. This puts both edges on a slant
in relation to the handle.
The reason a slanted blade or an oblique slicing motion such as the so-called Gillette slide works better is less-well understood, however, by most persons. Yet the reason is simple: when a straight blade cuts obliquely, the functional angle of the cutting edge itself is essentially reduced, meaning that its effective sharpness is increased. It is simple geometry; let me explain further:
If you picture the line that a pencil lead would trace as you cut it with any sharpened edge, a straight-on (perpendicular) cut would make a line up the blade that is perpendicular to the cutting edge. An oblique cut would make a line on the blade that is not perpendicular to the cutting edge -- it is, well, oblique. If you were to cleave the blade along those two pencil lines, you would see that the cross sections are different. The oblique-cut cross section has a longer, sharper point in comparison to the cross section cut that is perpendicular to the edge. This means that an oblique cutting angle makes any blade effectively sharper, more efficient in its work.
Another side benefit of the slant-bar design is that it may also tend to stiffen the blade, which may offset to some degree the potential harshness of its larger blade reveal. There are other subtleties to a slant-bar razor, but to cover them all would require its own article -- maybe on another day.
Let's review the more esoteric design aspects of a DE razor:
- Blade angle in relation to the shaving plane of the razor head
- Blade reveal describes how much of the blade is covered by the top cap of the razor.
- Blade exposure is the degree to which the blade edge is held underneath the shaving plane of the cap and safety bar, within their protective embrace.
- Razor gap is the distance between the blade edge and the safety bar.
- Blade stiffness (as determined by the razor design, not the blade itself) affects blade vibration while shaving.
- Edge slant is the degree that the blade edge deviates from square to the handle
- Safety-bar design (round cross section, scalloped bar, or open comb) can affect how easily the blade can contact skin and how much lather remains as blade slices stubble.
- Razor weight
- Razor balance
- Handle length & diameter
Is this single gap adjustment adequate adequate to manage harshness and quality of shave? It depends. If one needs a more aggressive cut, this can be achieved by opening the gap, but one then is left to deal with, most notably, whatever is the inherent blade vibration of the design and the fixed blade angle, which may be more harsh than the user's skin needs; this can be a problem for those with more fragile skin. If the user is unaffected by a higher degree of blade scraping and edge vibration, then the TTO's adjustment feature is completely acceptable.
Blades, too, vary in their characteristics, which are primarily two: sharpness and durability. (Technically, we could add third and fourth characteristics of smoothness and innate stiffness of the edge, but these are heavily influenced by razor characteristics, and utterly impossible for the average person to evaluate without being influenced by razor characteristics.) A sharp blade may be ground and coated (or not) in such a way as to be more sharp or less so, and to be smoother or less so on a given face and hair type, and in a given razor. Durability is probably the result of blade material, microscopic details of the edge grind, type of hair being cut, and the care of the blade between shaves.
If your head isn't spinning too much, then you might appreciate why the DE shaving experience is so subjective. Take the seven primary characteristics of a razor, add the three others (weight, balance, and handle length), then include the blade characteristics, and finally factor in skin and hair differences -- this explains how easy it may be for a shave to be less than optimal (and we haven't even considered shave prep and product variables).
Yet as one balances the design factors, the shave can be close, comfortable, and rewarding for those moments in the day that he completes the shave ritual. And this is how I hope it goes for you. Happy shaving!
Abbreviations: DE = double edge; TTO = twist to open