MAKING BRICKS WITHOUT STRAW

Dominion, Volume 14, Issue 73, 20 December 1920, Page 6

MAKING BRICKS WITHOUT STRAW

BIBLICAL PHRASE EXPLAINED,

One of the earliest of recorded mirikes was that of the Chosen People during the Captivity, when they were compelled to make "bricks without straw. The phrase has sorely puzzled Biblical commentators, and till quite recent years no adequate explanation ot the importance of the use of Btraw in brickmaking was forthcoming. One ot the most obvious suggestions, and one which has been generally accepted, .is that we straw was used as a mechanical binning agent to hoTcT the bricks toother. Bricks from l'ithom, one of the cities of tlio Captivity, have of late been subjected' to a searching analysis. lhat the specimens 'are authentically bricks made by hand, and sun dried MOO year* ago there is no doubt. But analytical and other investigations indicate no trace of straw in their composition. In fact, tho only striking point about these bricks is that their analysis is almost identical With thai; of mud taken from the Nile quite recently—n remarkable comment upon tho slowness, with which Nature makes her changes. Nile mud to-day is the same as Nile mud 3000 years ago; notwithstanding the' great! changes that period has seen in the -history of mankind. in the history of the earth it is but as a day. Tho work of the Amen-, can scientist! Dr. Acheson may throw some new light on this puzzle. TIII9 chemist had occasion to examine some specimens of German _ and American clays, .identical in chemical composition, but of quite different practical qualities. He found that tflie differences in their plasticity resulted from a mtterejice in their preliminary treatment. The (more plastic clay contained a greater proportion of particles so nne that they cannot bo settled from 'solution or 'even filtered by ordinary metliparticles, as they are callod by chemists. Treutmcnt of raw clay by water containing an abundance of colloidal matter results in a gn?atly improved plasticity of the clay, for it ' f ' found that the colloidal matter acts protectively upon tho finest clay particlcs, preventing them from aggregating into larger particles, as they naturally tend to do. So that if oJiy method of'preparation of the clay bo adopted which will increase this action, the clay will gain in tenacity and strength. 'me such method, long'adopted in some •■lay is to' trp«it < tho clay water containing tannin. Dr. Ach c son discovered that straw i'flclf contains nearly 50 per cent, of a. water-solublo colloid. It is therefore suggested that the old bflck makers of the Cuptmty i!id no; actually incorporate straw in their bricks, but that they treated their clayey Nile mud with an infumon of straw. Experiments havo so. far confirmed this theory.