I recently purchased two new Muhle DE razors. One is the R89 which has a solid scalloped safety bar. The other is the R41 which has a toothed bar a.k.a. open-comb. I was interested in determining how these performed. Using identical blades in both razors, I tried shaving with each, alternating on a nearly daily basis. In other words, if I had a Derby blade in the R89 with 2 shaves on it, I would compare that with the R41 charged with a (different) Derby, also with 2 shaves on it.
On a subjective level, I found the R41 open comb to be a consistently more aggressive razor than the R89 which I would describe as mild, yet very effective. Both razors are capable of accomplishing a BB smooth shave. That said, the R89 requires a little more operator effort (pressure) and more passes, especially around the jaw line. YMMV.
When you examine this pair of razors, it is immediately apparent that the blade geometry and exposure are pretty radically different. Ive tried to illustrate this in the accompanying pix.
In the R89, the blade is compressed against the curved top plate by a pair of horizontal pillars which are parallel with the long axis of the blade. These pillars are positioned to contact the blade at points which are ~6mm in from an edge. This arrangement results in the production of a distinct curve to the blade (concave downward) as the razor is assembled and tightened, and brings the cutting edge of the blade towards the scalloped safety bar. Using feeler gauges, I measured the gap between the blade edge and the bar when the razor is fully assembled to be 0.029 which is in close agreement with the Wiki tabulation citing a gap of 0.030 { http://wiki.badgerandblade.com/index.php/DoubleEdged_Safety_Razors_Ranked_by_Aggressiveness }.
By comparison, the open-comb Muhle has no horizontally oriented pillars to compress the blade into a concave down curve. Rather, the blade is compressed under a much broader zone between the curved spans of both the top and the bottom plates. The compression zone spans 18mm of the total 22mm edge-to-edge width of the blade. Compression of the central 18mm of the blade produces a small but distinct UPWARD curvature of the exposed 2mm of the blade on each side. This can be described as a mild ducktail bend when looking at the razor head from one end. Ive tried to illustrate this upwards bend in the lower two pix. It is this upward curvature of the blade edge that produces the gap between the blade edge and the individual teeth of the comb. However, the gap between the blade edge and the teeth of the comb is a mere 0.007 which is only ~25% of the gap on the closed comb R89. If one inspects the 1904 Patent Application of K. Gillette for the safety razor in the Wiki { http://wiki.badgerandblade.com/index.php/Image:Gillette_1904_patent.jpg } you can see that his prototype was also an open comb, and that the blade was compressed in a manner almost identical with the R41---compression extends to nearly the edge of the blade on both sides.
So, what does all this mean? The short answer is that I dont fully understand. What appears to be evident, however, is that simple blade gap is not what is responsible for the more aggressive behavior of an open comb razor vs. its safety bar counterpart. If gap were the determinant, then the safety bar razor at 0.029 should be ~4x more aggressive than the open comb at 0.007. Im thinking that the small but distinct upward curvature of the blade edge somehow contributes to its more aggressive behavior when placed against the skin at the proper angle. Somehow, that translates to more or better blade edge exposure. I am interested in what my fellow B&Bers think on this. What, for example, is the "gap" on other brands of open comb razors? Are they comparable to the R41?
On a subjective level, I found the R41 open comb to be a consistently more aggressive razor than the R89 which I would describe as mild, yet very effective. Both razors are capable of accomplishing a BB smooth shave. That said, the R89 requires a little more operator effort (pressure) and more passes, especially around the jaw line. YMMV.
When you examine this pair of razors, it is immediately apparent that the blade geometry and exposure are pretty radically different. Ive tried to illustrate this in the accompanying pix.
In the R89, the blade is compressed against the curved top plate by a pair of horizontal pillars which are parallel with the long axis of the blade. These pillars are positioned to contact the blade at points which are ~6mm in from an edge. This arrangement results in the production of a distinct curve to the blade (concave downward) as the razor is assembled and tightened, and brings the cutting edge of the blade towards the scalloped safety bar. Using feeler gauges, I measured the gap between the blade edge and the bar when the razor is fully assembled to be 0.029 which is in close agreement with the Wiki tabulation citing a gap of 0.030 { http://wiki.badgerandblade.com/index.php/DoubleEdged_Safety_Razors_Ranked_by_Aggressiveness }.
By comparison, the open-comb Muhle has no horizontally oriented pillars to compress the blade into a concave down curve. Rather, the blade is compressed under a much broader zone between the curved spans of both the top and the bottom plates. The compression zone spans 18mm of the total 22mm edge-to-edge width of the blade. Compression of the central 18mm of the blade produces a small but distinct UPWARD curvature of the exposed 2mm of the blade on each side. This can be described as a mild ducktail bend when looking at the razor head from one end. Ive tried to illustrate this upwards bend in the lower two pix. It is this upward curvature of the blade edge that produces the gap between the blade edge and the individual teeth of the comb. However, the gap between the blade edge and the teeth of the comb is a mere 0.007 which is only ~25% of the gap on the closed comb R89. If one inspects the 1904 Patent Application of K. Gillette for the safety razor in the Wiki { http://wiki.badgerandblade.com/index.php/Image:Gillette_1904_patent.jpg } you can see that his prototype was also an open comb, and that the blade was compressed in a manner almost identical with the R41---compression extends to nearly the edge of the blade on both sides.
So, what does all this mean? The short answer is that I dont fully understand. What appears to be evident, however, is that simple blade gap is not what is responsible for the more aggressive behavior of an open comb razor vs. its safety bar counterpart. If gap were the determinant, then the safety bar razor at 0.029 should be ~4x more aggressive than the open comb at 0.007. Im thinking that the small but distinct upward curvature of the blade edge somehow contributes to its more aggressive behavior when placed against the skin at the proper angle. Somehow, that translates to more or better blade edge exposure. I am interested in what my fellow B&Bers think on this. What, for example, is the "gap" on other brands of open comb razors? Are they comparable to the R41?