Forgive me if something like this has been done before - I haven't found it!
Razors have been described as "aggressive" or "mild", most frequently using "gap size" as the determining metric aside from personal experience. The same razor has sometimes received quite different assessments; e.g. I've seen Gillette Old Style varieties called mild or aggressive or even completely ineffective.
The Shave Wiki article (http://www.shavewiki.com/index.php/Image:SHAVE_ANGLE4.jpg) described the possible geometric factors involved. I think the angle from the handle is not relevant at all since that's entirely manageable by intuitive adjustments. I've tried to focus on three factors that might be observed in close-up photos:
(1) Cutting Angle, defined as the angle between the blade edge and a line tangent to the head cap and guard or comb.
(2) Exposure, defined as the protrusion of the blade beyond the tangential line described above.
(3) Gap, defined as the space between the comb plate and blade edge.
I initially analyzed seven razors as indicative of historical design development:
(1) Gillette Old Style (102 with thin cap).
(2) Merkur 11C, based somewhat on the above.
(3) Gillette "New Improved" (106).
(4) Gillette NEW with short comb (134).
(5) Gillette NEW with long comb (134 again).
(6) Gillette Tech, pre-WWII type.
(7) Gillette Tech, post-war type.
Photos follow.
Let's look at some base plates first.
This is the base plate of the Gillette Old Style (this example dates to 1908). Note the curvature which closely mirrors that of the cap - the blade is pressed against this plate and diverges over the span of the teeth, creating a small gap. The Merkur looks rather similar, so isn't shown.
Here's the base plate of the New Improved. A radical departure. Nicely machined flat center with abruptly machined dips over the comb portion. Blade flexes sharply over the edge of the base plate and angle is determined by the cap profile.
Here we have the NEW, short-comb version. (This really ought to be called "straight comb" I think.) Note the curvature which is reminiscent of the Old Style.
And here is the NEW, long-comb version. (This really ought to be called "droopy comb"...maybe?) A melding of design elements...central platform is near horizontal as in the New Improved but given some curvature; also has the dips of the New Improved but they are carried farther inland.
Now let's see how these differences play out in the critical factors noted above. The same blade was used in all photos (a Derby because it was already in one of the razors) and was carefully checked for centering.
Gillette Old Style. The red line parallels the blade near its edge, the blue line is the tangent described above. Note the very low cutting angle. Combined with that is a significant blade exposure. The gap is very small. There are two black lines showing the approximate range of effective cutting angles. That range is fairly low due to the small gap.
It might be worthwhile to consider exactly who King Gillette's potential customers were at this point. All straight-edge users. The contemporary ads confirm that. These men were necessarily accustomed to paying close attention to blade angle and pressure. That would change after WWI with razor kits donated to young recruits. But the geometry shown here might explain the range of descriptions now applied to these razors - if you used it at too high an angle it would be ineffective (not very forgiving of errors in that direction), if you used too much pressure it could be quite harsh, but if used with a light hand it might come across as fairly mild. If you do everything right, it can perform very well (or so I think) due to the low cutting angle. But it demands good technique.
Now here's a modern Merkur, rather similar to the above design. Note that the cutting angle has been increased, and there's no exposure (as defined here) at all! Plus the gap is really tiny! This razor shouldn't work at all, right? But it does. It works because your skin flexes. Just enough to let the blade cut with moderate pressure. That tells us something I think. More exposure requires less pressure. Less exposure is more forgiving on that score.
Now the New Improved. Brought out 1921. Perhaps more shavers by this point began their shaving experience with safety razors and found fault with the original design due to excess pressure (harshness) or inattention to angle? Here was the fix. Big gap was forgiving about angle of attack - might be less effective if used like a paint scraper but it will still take some hairs off. Slightly steeper cutting angle and no exposure - edge flush with the tangent line - perhaps to partially compensate for the potential harshness caused by skin pressing down into the big gap if you weren't careful with pressure. All that seems to fit with my experience anyway. A very effective razor but watch your pressure or it'll burn!
Here's the NEW Short-Comb. Gillette stayed with the 25 degree cutting angle and zero blade exposure of the N.I., but the curved base (like the Old Style) gave the blade more support on the bottom plate - might be related to damping micro-vibrations, but not space here to go into that. They also decreased the gap, perhaps because the N.I. had gone a bit too far in that direction for most users. This example is mid-late 1930s.
The NEW Long-Comb. The comb actually protrudes less than the former example creating some additional blade exposure. Same angle, similar gap. I'd expect this to be a little more "aggressive" or perhaps less forgiving about pressure, which fits my experience with it. Not sure about dates for short and long comb versions, but NEW types are circa 1931-41.
The pre-war Tech with the flatter base, kind of like the N.I. and NEW long-comb in it's "fulcrum" design. Similar angle (probably really 25 degrees, take my measurements as plus or minus a degree) and exposure. Seems like a cheaper way of making the NEW long-comb, stamping it out instead of machining and using a bar instead of comb, with slots to let cuttings and foam escape - but perhaps less effectively?
The post-war Tech. Reason it has a reputation as mild is clear - less blade exposure than above.
Comments, suggestions, criticisms welcomed.
- Bill
Razors have been described as "aggressive" or "mild", most frequently using "gap size" as the determining metric aside from personal experience. The same razor has sometimes received quite different assessments; e.g. I've seen Gillette Old Style varieties called mild or aggressive or even completely ineffective.
The Shave Wiki article (http://www.shavewiki.com/index.php/Image:SHAVE_ANGLE4.jpg) described the possible geometric factors involved. I think the angle from the handle is not relevant at all since that's entirely manageable by intuitive adjustments. I've tried to focus on three factors that might be observed in close-up photos:
(1) Cutting Angle, defined as the angle between the blade edge and a line tangent to the head cap and guard or comb.
(2) Exposure, defined as the protrusion of the blade beyond the tangential line described above.
(3) Gap, defined as the space between the comb plate and blade edge.
I initially analyzed seven razors as indicative of historical design development:
(1) Gillette Old Style (102 with thin cap).
(2) Merkur 11C, based somewhat on the above.
(3) Gillette "New Improved" (106).
(4) Gillette NEW with short comb (134).
(5) Gillette NEW with long comb (134 again).
(6) Gillette Tech, pre-WWII type.
(7) Gillette Tech, post-war type.
Photos follow.
Let's look at some base plates first.
This is the base plate of the Gillette Old Style (this example dates to 1908). Note the curvature which closely mirrors that of the cap - the blade is pressed against this plate and diverges over the span of the teeth, creating a small gap. The Merkur looks rather similar, so isn't shown.
Here's the base plate of the New Improved. A radical departure. Nicely machined flat center with abruptly machined dips over the comb portion. Blade flexes sharply over the edge of the base plate and angle is determined by the cap profile.
Here we have the NEW, short-comb version. (This really ought to be called "straight comb" I think.) Note the curvature which is reminiscent of the Old Style.
And here is the NEW, long-comb version. (This really ought to be called "droopy comb"...maybe?) A melding of design elements...central platform is near horizontal as in the New Improved but given some curvature; also has the dips of the New Improved but they are carried farther inland.
Now let's see how these differences play out in the critical factors noted above. The same blade was used in all photos (a Derby because it was already in one of the razors) and was carefully checked for centering.
Gillette Old Style. The red line parallels the blade near its edge, the blue line is the tangent described above. Note the very low cutting angle. Combined with that is a significant blade exposure. The gap is very small. There are two black lines showing the approximate range of effective cutting angles. That range is fairly low due to the small gap.
It might be worthwhile to consider exactly who King Gillette's potential customers were at this point. All straight-edge users. The contemporary ads confirm that. These men were necessarily accustomed to paying close attention to blade angle and pressure. That would change after WWI with razor kits donated to young recruits. But the geometry shown here might explain the range of descriptions now applied to these razors - if you used it at too high an angle it would be ineffective (not very forgiving of errors in that direction), if you used too much pressure it could be quite harsh, but if used with a light hand it might come across as fairly mild. If you do everything right, it can perform very well (or so I think) due to the low cutting angle. But it demands good technique.
Now here's a modern Merkur, rather similar to the above design. Note that the cutting angle has been increased, and there's no exposure (as defined here) at all! Plus the gap is really tiny! This razor shouldn't work at all, right? But it does. It works because your skin flexes. Just enough to let the blade cut with moderate pressure. That tells us something I think. More exposure requires less pressure. Less exposure is more forgiving on that score.
Now the New Improved. Brought out 1921. Perhaps more shavers by this point began their shaving experience with safety razors and found fault with the original design due to excess pressure (harshness) or inattention to angle? Here was the fix. Big gap was forgiving about angle of attack - might be less effective if used like a paint scraper but it will still take some hairs off. Slightly steeper cutting angle and no exposure - edge flush with the tangent line - perhaps to partially compensate for the potential harshness caused by skin pressing down into the big gap if you weren't careful with pressure. All that seems to fit with my experience anyway. A very effective razor but watch your pressure or it'll burn!
Here's the NEW Short-Comb. Gillette stayed with the 25 degree cutting angle and zero blade exposure of the N.I., but the curved base (like the Old Style) gave the blade more support on the bottom plate - might be related to damping micro-vibrations, but not space here to go into that. They also decreased the gap, perhaps because the N.I. had gone a bit too far in that direction for most users. This example is mid-late 1930s.
The NEW Long-Comb. The comb actually protrudes less than the former example creating some additional blade exposure. Same angle, similar gap. I'd expect this to be a little more "aggressive" or perhaps less forgiving about pressure, which fits my experience with it. Not sure about dates for short and long comb versions, but NEW types are circa 1931-41.
The pre-war Tech with the flatter base, kind of like the N.I. and NEW long-comb in it's "fulcrum" design. Similar angle (probably really 25 degrees, take my measurements as plus or minus a degree) and exposure. Seems like a cheaper way of making the NEW long-comb, stamping it out instead of machining and using a bar instead of comb, with slots to let cuttings and foam escape - but perhaps less effectively?
The post-war Tech. Reason it has a reputation as mild is clear - less blade exposure than above.
Comments, suggestions, criticisms welcomed.
- Bill
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