(Genesis 11:3; Exodus 1:14; Leviticus 14:42,45; Isaiah 41:25; Ezekiel 13:10,11,14,15; 22:28; Nehemiah 3:14) The various compacting substances used in Oriental buildings appear to be--
Bitumen, as in the Babylonian structures;
Common mud or moistened clay;
A very firm cement compounded of sand, ashes and lime, in the proportions respectively of 1,2,3, well pounded, sometimes mixed and sometimes coated with oil, so as to form a surface almost impenetrable to wet or the weather. In Assyrian and also Egyptian brick buildings, stubble or straw, as hair or wool among ourselves, was added to increase the tenacity.
"a wide-mouthed vessel in form of an inverted bell, in which substances are pounded or bruised with a pestle."--Webster. The simplest and probably most ancient method of preparing corn for food was by pounding it between two stones. The Israelites in the desert appear to have possessed mortars and handmills among their necessary domestic utensils. When the manna fell they gathered it, and either ground it in the mill or pounded it in the mortar till it was fit for use. (Numbers 11:8) So in the present day stone mortars are used by the Arabs to pound wheat for their national dish kibby. Another word occurring in (Proverbs 27:22) probably denotes a mortar of a larger kind in which corn was pounded: "Though thou shouldest bray a fool in a mortar among wheat with a pestle, yet will not his foolishness depart from him." Corn may be separated from its husk and all its good properties preserved by such an operation, but the fool's folly is so essential a part of himself that no analogous process can remove it from him, and you can find more about that here on st-takla.org on other commentaries and dictionary entries. Such seems the natural interpretation of this remarkable proverb. The language is intentionally exaggerated, and there is no necessity for supposing an allusion to a mode of punishment by which criminals were put to death by being pounded in a mortar. A custom of this king existed among the Turks, but there is no distinct trace of it among the Hebrews. Such, however, is supposed to be the reference in the proverb by Mr. Roberts, who illustrates it from his Indian experience.
Main reference: Smith's Bible Dictionary (1860s)
Bible Gallery and Bible Illustrations (thousands of images)