Chalk-Making using Ash Wash and Plaster of Paris

Abstract

The study was an experimental venture in chalk-making. lt made use of an indigenous welding shop waste material called ash wash, and Plaster of Paris. Two formulas or treatments were used in the preparation of the chalk, Formula A used 70% Plaster of Paris and 30% ash wash; Formula B had 60% Plaster of Paris and 40% ash wash. Both formulas utilized a 200-mesh sieve so that two treatments of chalk were obtained. Five casts of sample chalk were prepared on each treatment for quality evaluation based
on texture and strength. Thirty-seven faculty members from five academic units in UNP served as evaluators. Each faculty- evaluator was provided 50 pieces of chalk on each formula or ten pieces each of the 5 casts of chalk prepared on the two formulas. Production costs were determined and compared to the present market value of the commercial chalk. On Formula A, the 1000gram mixture (or 1 kilo) produced 214 pieces of chalk. A 50 kilogram mixture on Formula A (equivalent to one sack) would produce 10,710 pieces or 74.375 boxes of chalk. About seventeen castings (16.66) were made out of a 1,000-gram mixture on Formula B. One casting produced 15 pieces of chalk and the whole 1,000 gram mixture produced 250 pieces. One sack Plaster of Paris (50 kg) would produce about 12,500 pieces or 86.86 boxes of chalk. The total production cost of each formula was four-hundred eighty pesos (P 480.00). Unit cost on Formula A was about thirty-five centavos (P 0,045) and cost per box was over six
pesos (P 6.45). On Formula B, unit cost was about four centavos ( 0.38) and cost per box was over five pesos P 5.53). The commercial chalk was more costly at eighteen pesos and fifty centavos (P 18.50) per box or at thirteen centavos ( 0,13) per piece of chalk.