Alum

Don't know for sure, but there really should be very little difference, if at all. Maybe cheaper blocks come from deposits with more contaminants?

Styptic pencils are different though, in that they have a much more multicrystalline structure -- they will crumble when wetted in use... No good for general AS use, only to topically treat cuts.
 
Are they not made by simply mixing potassium & aluminium sulphates these days?

Looking at the structure of the blocks from India and the expensive ones - it looks to me like the Indian ones are from moulds that are heated from the outside to encourage the crystallisation - I guess this is done more quickly in India by "natural" (sunlight) means than it is in (say) Osma's factory so the crystals in the Indian blocks are generally larger and less uniform.
 
Don't really know - they can either be manufactured from potassium, aluminium and sulfate, or from alunite mineral. I have no idea what the standard source is.

From Wikipedia:
Production

Alum from alunite
In order to obtain alum from alunite, it is calcined and then exposed to the action of air for a considerable time. During this exposure it is kept continually moistened with water, so that it ultimately falls to a very fine powder. This powder is then lixiviated with hot water and sulfuric acid, the liquor decanted, and the alum allowed to crystallize. The alum schists employed in the manufacture of alum are mixtures of iron pyrite, aluminium silicate and various bituminous substances, and are found in upper Bavaria, Bohemia, Belgium, and Scotland. These are either roasted or exposed to the weathering action of the air. In the roasting process, sulfuric acid is formed and acts on the clay to form aluminium sulfate, a similar condition of affairs being produced during weathering. The mass is now systematically extracted with water, and a solution of aluminium sulfate of specific gravity 1.16 is prepared. This solution is allowed to stand for some time (in order that any calcium sulfate and basic ferric sulfate may separate), and is then evaporated until ferrous sulfate crystallizes on cooling; it is then drawn off and evaporated until it attains a specific gravity of 1.40. It is now allowed to stand for some time, decanted from any sediment, and finally mixed with the calculated quantity of potassium sulfate, well agitated, and the alum is thrown down as a finely-divided precipitate of alum meal. If much iron should be present in the shale then it is preferable to use potassium chloride in place of potassium sulfate.

Alum from clays or bauxite
In the preparation of alum from clays or from bauxite, the material is gently calcined, then mixed with sulfuric acid and heated gradually to boiling; it is allowed to stand for some time, the clear solution drawn off and mixed with acid potassium sulfate and allowed to crystallize. When cryolite is used for the preparation of alum, it is mixed with calcium carbonate and heated. By this means, sodium aluminate is formed; it is then extracted with water and precipitated either by sodium bicarbonate or by passing a current of carbon dioxide through the solution. The precipitate is then dissolved in sulfuric acid, the requisite amount of potassium sulfate added and the solution allowed to crystallize.
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I thought they all just grew the crystals from potassium alum sulphate powder/crystals. Seems like an easy enough thing to do; I've even bought some to try it myself. I'm no expert though.

I just know I like to use it as the first step to my 'aftershave routine' after the cold rinse at the end of the blade-work. They all feel pretty much the same to me.

... oh, and you can sometimes find good deals on ebay for the stuff from various sources.
 
Deo alum can be potassium alum as well as ammonium alum. I use the potassium alum as a deodorant, as I seem to have a bit of a sensitivity to the the ammonium alum.

It's an ages old natural multi-purpose mineral salt. It also gets used in pickling, and cooking & baking, as well as other stuff if I remember rightly.
 
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