The Razor II
The hollow grinding procedure
In principle, it is not important which grade of hollow grind is used, as long as only the cutting edge and the back will touch the hone or strop. In theory, this would already be the case with a grinding wheel of 40 cm diameter, but this is not yet the perfect hollow grind, it is called a 'light' hollow grind or 'flat' grind. The disadvantage is, that in the hand of the layman, including the barber, this 'flat' hollow grind blade rapidly thickens in time after some years of honing. This blade would become dull soon, and could only be resharpened with coarse followed by fine hones. This would take a lot of time and the avarage user would spoil the blade. Another disadvantage is that these blades are very heavy.
The full (1/1) hollow grind has the opposite effect in the hand of the expert or skilled layman. The edge becomes sharper (the razor gets 'settled'), easier to use, and the slight vibration of the edge caused by the belly increases its effect. Errors will be detected immediately and slight damages to the edge can be repaired easily. The razor is light and easy to use, and can be used for an unlimited period of time without regrinding on the wheel. Shaving is smooth and painless - provided that the user follows some rules.
One of those rules is the to conserve the thickness of the back, which should be the blade width divided by 3,5. The hollow grinder divides the blade in two halfes: the upper part is hollow, the lower part is a biconvex belly. The biconvex part consists of the edge, the thinning and the belly. The biconcave part of sole, the hollowing, the back and the stabilizing piece. The sole is the thin transition between the belly and the hollow part.
The end result is a smooth transition between the parts and
parallel shadows when keeping the blade in the light. The shadow
moves when rotating the blade, and must keep its width at every
place of the blade. During stropping or when rubbing the thumb over
the edge, the 1/1 hollow grind blade gives a ringing sound
(therefore the designation 'singing razors').