Originally Posted By Dirtydog:
I may bicker with a couple in the middle, but this looks pretty much straight on. JMHO

Feathers are definitely in a category of their own. Some don't appreciate them and feel a bit intimidated. They can cut you quick.

 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 

 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 


 
 
 
 
 

Blades Sharpest to Least by Overall Average from New to After Second Shave	Sharpness New	Sharpness After First Shave	Sharpness After Second Shave	Sharpness Average
BIC Chrome Platinum -	40	33	32	35
Perma-Sharp Super -	41	30	37	36
Gillette Nacet Stainless -	39	35	38	37
Feather -	32	40	40	37
Gillette 7 O'clock Super Platinum (Black) -	45	32	36	38
Wilkinson Sword (German) -	46	33	34	38
Personna Platinum (Israeli Reds) -	41	37	36	38
Crystal -	44	37	38	40
Personna Comfort Coated (Lab Blue) -	48	37	35	40
Astra Super Stainless -	43	38	40	40
Rapira Platinum Lux -	44	38	39	40
Gillette 7 O'clock Permasharp Stainless (Green) (India) -	45	35	42	41
Gillette 7 O'clock Super Stainless (Green) (Russia) -	45	38	40	41
Gillette Platinum -	45	38	39	41
Wilkinson Sword (Gillette) -	43	40	41	41
Voskhod -	42	41	39	41
Gillette Silver Blue -	46	41	35	41
PolSilver Super Iridium -	46	39	40	42
Gillette 7 O'clock SharpEdge (Yellow) -	46	43	42	44
Kai Stainless Steel -	53	42	39	45
Gillette Rubie Plus -	50	45	41	45
Sputnik -	52	43	44	46
Treet Platinum -	45	46	46	46
Astra Superior Platinum -	49	46	44	46
Rapira Swedish Super Steel -	47	48	47	47
Big Ben Super Stainless -	49	45	49	48
Derby Premium -	51	46	46	48
Derby Extra (Green) -	53	44	51	49
Bolzano Superinox Inossidabile -	52	46	49	49
Merkur -	53	51	46	50
Shark Super Stainless -	47	51	56	51
Rockwell Razors -	54	51	54	53
Treet Carbon (Black Beauty) -	52	62	69	61
Super Tian Li Blue Blades -	67	61	60	63

Blades not yet tested:
7 am Hi-Platinum
Dorco ST-300 Platinum
Dorco ST-301 Stainless
Ladas Super Stainless
Lord Super Stainless
Rapira Stainless Chrome
Rapira Super Stainless
Schick Premium
Shark Super Chrome
Treet 7 Day Platinum
Treet Classic
Treet Dura Sharp
Treet King Super Stainless

The Test:
A digital scale is purposed to hold a clip with a pre-tensioned piece of test media. The blade edge (in this case a razor blade) is then pushed against the test media until it is severed. The scale is programmed to record the maximum force required to cut the test media.

The logic is that the lower the force required, the sharper the blade. The grams required to sever the test media is then considered to be the sharpness value.

To be consistent, a jig has been fabricated to hold the razor blade. Brass strips are used to make sure there is no bend in the blade, and the blade itself is affixed to sliding rails to make sure all the blades sever the test media clip at exactly the same angle.

Due to the sensitivity of such fine values and some very slight variations in the blade edge, a truncated mean (average) will be used. You can see in the picture below that the razor blade edge is not perfectly consistent all the way across.

4 readings are taken from each side of each blade, and the highest and lowest overall reading will be discarded. The average of the remaining 6 readings will be the given sharpness value for the blade. The logic to this type of statistical average is that if there is one significant outlier reading, it will not significantly impact the overall average.

Razor Blade Durability (Edge Sharpness Retention):
This test is designed to see how long a blade will last, and the consistency of the shaves.

Each blade will get its initial sharpness value based off 6 readings. I will then shave once, and then take 6 more readings (I will be as prudent as I can to ensure I am using both sides equally). I will then shave one more time, and then take 6 more readings after the second shave.

This will give a factor for how long each blade can retain its initial sharpness, and might provide some insight as to how many times you can use a blade.

The factor will be (current reading/previous reading), so a factor closest to 1.0 will be the most consistent. A factor of 1.0 will mean the blade did not lose any sharpness, a reading of 2.0 will mean that it took twice as much force to sever the test media, so the blade is essentially half as sharp as it was. A factor of 0.9 means that the blade edge is about 10% sharper than it was.

Again, note that this will have no bearing on the blade coating or smoothness, so the blade may loose smoothness while still retaining edge sharpness.

Of course, YMMV (your mileage may vary). Please note that I shave my head and my face, so each one of my shaves may be equivalent to two of someone that is just shaving their face. I also have relatively strong growth, except for the top of my head. To be consistent, all shaves will be done using 48 hours of growth (+/- a couple hours) using a Merkur 34C.

After the second shave I usually toss my blade regardless, which would equal about 4-5 face only shaves (I shave my head and face). Once the baseline testing is completed for all the blades (initial sharpness and after 1 and 2 shaves) I plan to return to some of the blades and see just how many shaves they can be pushed.