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Photo Analysis of Razor Designs

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
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Your post helped me understand why some razors seem to give me a better shave than others, even when using the same blade, thanks!
Excellent work! This post needs to be moved to the Wiki or somewhere easily found. It is very informative and deserves to be seen with all the other great work by members.
Nice work. It's cool to see people want to know everything about shaving. Especially the technical stuff. It's even better when they share!
Great post and thank you for taking so much time to produce those superb photos.

I need to study this more and reflect on my experiences, but you have done a great job of bringing the various factors together that control the shaving experience for each head. I've thought that exposure, as you define it, has to be more important than gap in "aggressiveness" and you illustrate the trade offs nicely. My gap measurements on the razors I have did not jive with my impression of my shaves. Those small difference make a huge impact on shaving.

Before I abandoned it for open combs, I played with different settings on my fat boy and ended up using it on 9 exclusively, but noticed that the blade angle changed quite a bit as I dialed it up along with the gap. Could never figure out if the changes in shaving were due to the gap changes or blade angle. Can we get you to analyze an adjustable at different settings in the manner you have presented?
Bill, this is the most logical and comprehensive analysis I've seen. Thank you for the time you spent on your analysis - a primer for all DE shavers!! :001_smile
Awesome!! I was going to request this exact post. As someone who is brand new to DE shaving, it's nice to gt a good explanation of what makes a razor aggressive.

Thanks again. Great info.
Excellent work!!

Do you have plans to do any more razors? I could spend hours looking at stuff like this.

Thanks to all of you!

I wanted to see reactions and suggestions, then explore:
- Old Style pocket set razors
- Red Tip Super Speed (only SS I have)
- Slim Adjustable at several settings.

Beyond that, the others I have fall under the same types as the ones shown in the analysis. But I may acquire more kinds and rope them in too!

By the way, lines were positioned while finer, then made wider so they'd show up at resolutions visible in posts. There's more detail than you can see in some of the pictures...just wanted you to know that because it may be hard to understand how I knew where the blade ended! I had to shoot about 15 or 20 exposures to get one that was in focus and exactly aligned.

- Bill
Nice study, and well illustrated! I have wondered what characteristics led to that "just right" shave. After trying a few DE razors I started to measure some of the gaps and make notes. I then stopped because I worried it would sway my impressions of the different designs due to preconceived opinions. I now know which ones work for me, so it is a good time to expose the "science" and figure out what's what. The new Muhle head works best for me, so I would be interested in discovering what they are doing with that design. By eye it looks as though they are using big spaces to expose the blade allowing it to cut when pressure is applied. Real measurements would be needed to verify that. I have found that razor works best with a heavy handle.
Thanks, and keep up the good work,
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