Thread: Crocus finish or Satin?

Originally Posted by hatzicho

Well colors of the ready to use pastes you can buy are vacant these days. The incredients differ from producer to producer, there are green pastes that are much coarser than the normal chromium oxide and so on.
I never use ready to use pastes, I produce all pastes that I use by myself, based on old receptures from grinders and my own experience. You can buy nearly all grinding and polishing powders as pigment.
So chromium oxide green is nearly all the same concerning the average or maximum particle size, that is around 0.3 µm. Concerning the red iron oxid Fe2O3 you can get variable particle sizes between 0.07 µm - which is much finer than chromium oxide - and > 1 µm.
You are correct that the ancient Sheffield polish was a mixture of several iron oxides that was mined as a natural product. It was developped around 1700 by the swedish engineer Christopher Polhem. The Solingen grinder Daniel Peres did a lot of efforts and years of experiments to recreate this polish by mixture of different iron oxides beginning of the 19th century.

Indeed the particles of red iron oxide are not as stable as chromium oxide particles. But that is also part of the trick, the particles getting smaller during polishing and therefore create a more mirror polishing. The problem is, that the surfaces must be very well prepared and nearly already without deeper scratches to use iron oxide. Otherwise you simply polish the scratches - which makes them even more visible on the surface.

As for the time you need for ploshing that is hard to say. If the surface is well prepared you can do the job quite quickly. But it is necessary that the metall surface heats up, therefore a certain pressure is needed. But I found that polishing with iron oxide you don't need so much pressure and time as when you polish with chromium oxide.

Regards Peter

Interesting point there at the end about the metal heating up in polishing. Something I've noticed is that when using a coarser polish like an emery you really want the metal to be cool, I've noticed that if you get a lot of heat build up that you get a kind of tearing out of the metal, under a loupe you get these tiny pock marks with a comet tail effect which is very noticeable as you move to finer and finer polishes. But when you get to the fine polishes you want some heat in the work to almost create a burnishing effect. Maybe it's the same smearing but just on such a fine level it seals the metal somehow. I wonder if this is the reason that, at least in my experience, you never see a full mirror finish on full hollow/thin grind razors, that the pressure and heat needed for a nice polish might ruin the temper or flex the blade too much? I think some makers do polish but it is very light and you can still see the very fine lines from the grinding/glazing operations.


Can you share anything about the compounds that you make? I've always wondered how they used to do stuff in the old days. Kind of incredible some of the things you see from then. I have an amateur interest in pocket watches and when you look back to some of the quite old verge-fusee escapement pieces, the level of polish on the steel parts is amazing considering what they had to work with. But then again it seems our forebears were more advanced than we are aware, so much has been lost to history.