Comminution (kom"i-nu'shun) is the act of breaking or the condition of being broken into small fragments which is exactly what this pharmaceutical term implies when it comes to processing raw herbs. Comminution is the pharmaceutical process of reducing the raw herb or mineral into particles. This act is necessary in order to obtain the highest degree of extract and to facilitate the action of the solvent or menstruum in the process of extraction. We all know in cooking that a lump of gravy powder or something similar which we would like to dissolve into a solution is always hindered when we do not break this lump up before dropping or adding a liquid. The same holds true for whole herbs. Various mechanical processes are used by old time pharmacists and all herbalists to facilitate an herb's extraction. One of the most common, is the use of the mortar & pestle ( trituration). Another closely related process is called contusion which also can involve a mortar & pestle, but this time, this mortar & pestle is made of iron and used in a striking manner. One can also use rasps/grates, various slicing/cutting/chopping blades, and even more various grinding and pulverizing machines, common or not so common to the everyday kitchen. The final goal is always to reduce the whole plant into smaller pieces to allow the solvent to circulate around and into the plant's structure for the process of the most efficient form of medicinal property extraction.

     As an herbalist, I tend to use several techniques depending on the characteristics of the plant which I am trying to process. I own a large antique cast iron mortar & pestle that can often be picked up at antique stores or online auctions very easily.

     These types of heavy iron mortars are excellent for initial processing of tough roots and nuts. For less hard herbal products, one can resort to using a Wedgwood type of mortar & pestle designed for a grinding action (trituration), rather than a striking one (contusion). The mortar and pestle can be made out of many materials. Glass ones are designed for preparing solutions of chemical substances in a liquid solvent. Wedgwood can be used for comminution of crystalline solids or generalized grinding of softer herbs. Because Wedgwood has a porous surface, make sure there is not cross contamination when grinding various batches. Porcelain mortars will be less porous than Wedgwood and probably the best for blending a mixture of powders to uniform sizes. Generally, mortars and pestles should not be interchanged as they are individually fitted to each other. Their efficiency depends on the maximum contact surface of each.

     Before subjecting your whole raw herb to either of these processes, it may be easier to slice them up using various cutting implements, i.e. knives, cleavers, or more industrial type of cutters as the antique tobacco cutter, again, often seen in antique shops in the areas where tobacco was once a farm crop. The tobacco cutter makes an excellent slicer of tough herbal parts before it is subjected to more refined grindings.

     I have found many commonly available kitchen type processors excellent substitutes and additions to an herbalist's tool chest in performing comminution. You can usually pick up second hand food processors at local garage sales that will slice up soft plant parts very nicely. The tougher parts will need more industrial constructed grinders, like the Vita-mix or Blendtec which usually have a higher price tag, even in the used market. Nevertheless, they can be excellent machines for further processing of raw herbs. In the antique side, one can pick up a number of different types of grinders that will work very efficiently by hand. Various old time coffee grinders and grist mills work quite nicely on very hard, not easily pulverized roots and nuts. Sometimes they can be picked up at flea markets very reasonably.

     General Rules for Operating Hand Mills----Much of the dissatisfaction experienced in operating hand mills has arisen from improper methods of using them or from failure to measure accurately the degree of resistance to disintegration possessed by the substance to be ground. One of the first requisites as before mentioned, is to dry the substance as perfectly as its physical character will permit without injuring it. If coarse, bulky, fibrous roots, barks, or similar substances are to be ground; they must first be cut or bruised. Most substances are ground with less labor, if they are first passed through the mill with the coarse adjustment, returning the portion which is sifted out, for regrinding, after setting the plates more closely together. This plan is repeated until the whole is ground. Care should be taken not to feed the substance into the hopper faster than it can be ground. The desire to get through quickly is the most frequent cause of clogging the mill and when this occurs much time is lost and the operator is strongly reminded of the well worn proverb about undue haste. If a considerable quantity is to be ground, two persons can operate the mill to better advantage then one, ---one feeding the mill carefully, the other supplying the physical labor and after the expiration of a given time, exchanging places. Good judgment is necessary in determining the rapidity with which substances can be fed into the hopper. Resinous or oily drugs, or substances which soften by heat, require very careful treatment and cannot be fed rapidly; dry ligneous barks or roots, on the other hand, can be fed as rapidly as the extent of grinding surface of the mill and the muscle of the operator will permit. The mill should be thoroughly cleaned after each operation, particular attention being given to the grinding plates. In the case of substances which form hard lumps by heating or clogging up the plates, the quickest way is to use boiling water to soften or dissolve the lumps; the plates should then be quickly dried, to prevent rusting. By running sawdust, bran, or rice chaff through a mill, after an odorous drug has been ground, it may be speedily cleaned and freed from odor. (Remmington's Practice of Pharmacy, 1926)