Bio-Diam 6 Regular Grit, 6 micron (YELLOW): For refining of edge direct from the hone; intermediate to coarse action or restoring.
Bio-Diam 3 Regular Grit, 3 micron (GREEN): For refining of edge direct from the hone; intermediate action or restoring.
Bio-Diam 1 Fine Grit, 1 micron (RED): For regular use on razor's edge.
Bio-Diam 0.25 Extra Fine Grit, 0.25 micron (SILVER): For regular use and super-fine finishing on razor's edge.
Diamonds are the hardest substance known to man; far harder than any steel yet developed. Industrial-grade diamonds, similar in hardness to gemstones, are biproducts of the diamond mining industry. Their flaws, color inconsistencies, or other characteristics make them unsuitable for jewelry. Also in the process of cutting and polishing gemstones, significant waste is produced. When all of this is crushed into a fine powder, the resulting particles acquire irregular cutting edges. Being harder than any other substance, the particles hold those edges longer than any other material. This diamond powder does the actual work of sharpening.
However, all diamond compounds are not created equal. The best are very carefully controlled in manufacturing to assure consistency in the size of the actual particles. For example, a compound classified as "one micron" though it may have particles smaller, should contain no particles larger than one micron. This is important, especially in a close-tolerance application like producing a highly refined razor edge. All the diamond particles used in Thiers Issard "Bio-Diamond" Sharpening Pastes are very carefully sorted to make sure that particles in each mix are exactly the given grade size.
Another differentiation between compounds is the carrier paste. In an industrial polishing application, an oil-based carrier (typically a petrochemical) may be acceptable. In sharpening a straight razor, a water-based paste is preferable. This will easily rinse away after sharpening, lessening the risk of any skin irritation or infection."Bio-Diamond" Pastes are water-based, perfect for use in the sharpening of razors; they have no harmful chemical additives and are even "food-safe" if accidentally ingested.
IMPORTANT: A razor's edge can actually be too sharp which can be a result of over-sharpening with diamond pastes. Such an edge will catch on every surface imperfection in the skin, causing irritation and razor-burn. For a close yet comfortable shave, the razor's edge should glide over the skin, barely touching, catching only at the base of the hairs to be cut. Generally using a diamond compound as fine as or finer tan 0.5 micron can result in an over-sharpened edge. In most cases, one micron or smaller diamond pastes are more than capable of sharpening a razor that has become dull through normal use. By starting with an even coarser grit (in the 6 micron to 1 micron range) depending on how dull the beginning edge is, you can refine the "not quite shave-ready" edge typically found on a new, out-of-the-box razor. Before sharpening a new razor, first try shaving with it. If it pulls, drags or is in any way uncomfortable, sharpening is required. By this test, you learn how much sharpening to do. Generally 20 round-trips on each side of the diamond-pasted strop will get it right. If after sharpening and again trying to shave, it needs more work, repeat the process. You may have heard of many different ways to test the sharpness of a razor; the hanging-hair test, the standing-hair test, shaving your forearm, etc. But, the only true test is actually shaving with it.
In most cases, a good 4 sided paddle-strop, or one or more 2 sided strops and several different grit diamond sharpening compounds (typically about a 1 micron grit followed by 0.25 grit) will be all that is needed to maintain a fleet of daily shavers. What diamond paste will not do alone is establish a basic working edge on a razor that hasn't seen a strop in 50 years or remove a ding or chip (the result of dropping the razor or some other accident). For such a repair, only a hone will do. But, once a hone has done the heavy work, diamond sharpening pastes (this time a 6 micron grit to a 3 micron, followed by 1 micron and finally 0.25 micron) will refine the basic edge more quickly and in a much more controlled manner than a hone can.
The multi-step Bio-Diamond strop procedure every 2-3 weeks should keep your razors in perfect shaving condition.