Clovis, allow me to suggest that your suspicion is indeed correct. This post may be long and "wordy" but bear with me.
What you have is called “variances in manufacture”. There are variances in all stages of manufacture.
Variances in raw material: In the case of razor steel, the amount of carbon in the steel has an influence on the hardening characteristics of the steel, Even today, it is difficult to determine exactly how much carbon is in a sample of steel, and suppliers will state anywhere between .08 and .12 percent (hope I got those decimal places right)
Variances in treatment: After the blade is forged it must be hardened and then tempered by heat. The temperature of the heat also has an influence on the hardness, toughness and crystal structure of the blade and the resulting edge.
Many vintage cutlers didn’t have precision thermometers (thermocouples), so an experienced workman would gage the heat by looking at the changing colors of the blade as it is heated to determine when tempering was done… as it is human nature… he may be spot on in the morning just after breakfast… perhaps not so just before lunch.
Because of these variations (and others) a razor may be hard, medium or soft (and in this case, by “soft” I am not referring to a blade that “lost its temper” from overheating).
Hard Steel (hard blade) will resist abrasion, so that would explain why the slurry takes longer to darken. A hard blade will take a cutting edge, however hard steel tend to be brittle, and so there may be microscopic chips at the very edge, that would explain the skin irritation.
In the case of hard steel a suggested solution is to use a strip of tape on the spine, this will make the bevel angle more obtuse, the edge will have “strength from volume” and thus reduced micro-chipping (incidentally, a pasted strop may also do the same).
Soft Steel is easy to sharpen (relative to hard steel) so the slurry will darken faster (again relative to hard steel), and will tend to shave with less irritation. Some folks much prefer the “smooth?” shave offered by soft steel however, it will require more frequent touch-up than hard steel.
Medium Steel is somewhere in between the two, some folks will say it the best of both worlds.
Now I must mention there exists razors with Flawed Steel, and are less suitable for shaving live-human whiskers.
Steel that is Too Hard or Brittle, may not have been tempered sufficiently or its crystal structure may have been injured previously during forging or hardening. When sharpening such a blade, the edge will have tiny notches (chips) just visible to the naked eye, and despite your best efforts (and equipment) will not produce a clean notch-free edge… and as you can well imagine, the resulting shave will not be satisfactory. A solution to this condition may be possible, but it’s not worth the effort.
Steel that is Too Soft is at the other extreme, it may have “lost its temper” from over heating during polishing or grinding, or simply was not sufficiently hardened to begin with. Such steel is very easy to sharpen, but will often produce wire or “filmy edge” as if there is a fin attached to the edge. Such an edge if successfully sharpened will not hold a keen cutting edge for long. Again, as in steel that is too hard a solution is not worth the effort.
Finally… Don’t place too much faith in marketing BS from anyone who tries to sell you something. Believe me, they will tell you the item is virgin, rare and the best thing since sliced bread (hint: you need it, and you should quickly pay the premium to secure it before someone else gets the better of you).
But with that said, I believe razors for Tough Whiskers and Tender Skin will have a slightly thicker spine in proportion to the width of the blade, and the steel will be Hard or Medium tempered. Razors for Soft Whiskers and Tender Skin will have Medium to Soft temper. Of course for Soft Whiskers and Not-So-Tender Skin, almost any razor will do.
But as fate would have it... it is difficult to determine the hardness or softness of steel by looking at it, and equally difficult to determine the hardness or softness of whiskers or skin (relative to who
)... so we should try different razors until that special one is found… then nothing else matters… of course, in so doing, it’s good to have a return guarantee… just in case. :thumbup:
