So we've established that a coated stainless blade with a noble metal edge is the pinnacle and has been for 60+ years. I wonder what drives the difference in face feel between different manufacturers of this type of blade? Grind angle or perhaps the quality of their manufacturing?
Point 5: All the talk about needing super sharp blades is fiction (a PTFE coating is superior to extra sharpness and sharp pointy edges wear down quicker.)
Even empirically super-dull blades like the Astra Super Platinum are considered "sharp" presumably because of the good coating that they have and the platinum edge retains that sharpness (dullness) throughout the shave; whereas an empirically super-sharp blade like the Feather Professional can be considered spent after a couple of shaves as that super-sharpness is gone within a few strokes on the face.
Face-feel is likely the coating, or number of coatings (teflon, polymer, single, double, triple, multiple); longevity, simply down to hardening of the edge (tugsten, platinum, iridium, chromium, sputtered or cryo-applied).
My instincts, after just a few years of limited DE experimentation, is that prep makes more of a difference than any other factor. I could never figure out why a modest Derby Extra can give a lovely BBS shave "sometimes" and not others, and i didnt think my technique was that erratic.
I used Feathers and got mixed results - clearly sharp, but not translating into a super close shave every single time. Putting aside the "feeling" of the shave on the skin, could not quite equate why i wasn't always getting the fabled BBS.
To me, the Astra SP "feels" almost as sharp as the Feather, yet much, much smoother and gentler on the skin.
I believe that somehow ANY blade can, on a microscopic level, "bump" and "skip" across less than perfect skin and hair preparation and so give a less than satisfactory shave.
I also suspect there must be some strange relationship, down at that level, between the blade coating and the soap / cream used and there is probably an optimum thickness of soap /cream coating on the face to get the best shave.
This is very interesting reading. Especially as I have a foot in the DE and SR camps. I kind of intuited that sharpness in and of itself wasn't the only factor because sometimes with a straight if it has a really good edge it feels smooth rather than sharp but still slices the hairs effortlessly. No coating on a straight so it seems that stropping, prepping and good lather are the major factors. Stropping is admittedly edge refinement which contains an element of polishing and 'sharpening' (mostly realignment). So I am not surprised that the article above cites prep and non-stick blade coating as the primary drivers of comfort. Longevity is a separate thing, although for a blade manufacturer, equally important.
I'll have to pay closer attention to the DE blades I use. I have a few different ones.
I've revisited my short list of absolutely must have blades and I can't spot any sort of pattern ...
I've got the Chinese Super Gillette Blue, the Permasharp Super ... good so far. Rapira Platinum Lux, go figure! Treet Platinum, SuperMax Super Platinum ... okay, so perhaps a (faux) platinum thing going on? Nah, coz then there's the very plebian Vidyut Stainless (Economy) and the Wilkinson Sword Economie, which I prefer over the regular Wilkinson Sword. Silver Star Super Stainless. Treet Durasharp. Personna Comfort Coated, which makes sense as I really don't like the Lab Blues and Med Prep < remind me, they're uncoated? One washed? But prefer the regular stainless over the Personna Platinum Chrome.
Maybe I've a Jekyll and Hyde thing going on?
Given that the Treet Platinum is "platinum class" rather than platinum edged and I think that's true of the Rapira, too; perhaps also of the SuperMax, although I'm not sure what they sputter on so maybe that's the anomaly. The rest are simple stainless, with an erring towards the pedestrian. The Treet Durasharp is a modern carbon blade with PTFE coating. Personally, I've not seen them rust across 5 or 6 shaves and pulling old ones out of my blade bank, I'm not seeing rust. I do see rust on the crappy Vidyuts, though! Stainless???
All Personna blades are coated to the best of my knowledge. I think you are possibly confusing blade coatings (PTFE, or derivative thereof) with edge alloys. Platinum, Chromium, etc., are not coatings, but edge hardening treatments. The Treet "Black Beauty" is the only modern uncoated DE blade I know of.
I don't have but one highly polished razor, the RR GC .68, which I use sparingly. I think perhaps the bentonite clay, or some other artisan soap additive, can cause as you say "judder".
Yeah, it okay ... I know harder metals are "sputtered" onto the edges. Nah! It's more the "comfort coated" moniker as somehow distinguishing it from its peers. Both Meds and Labs feel horrific to me, and I can happily shave with a Black Beauty (in fact did just that a mere few days ago). What with prepping bodies for surgery or slicing up specimens in labs, I can't see a need for coating on either.