=Reductions.= The single pigment paints, such as white leads, were reduced by the so-called ounce system, each ounce of oil added to 12-1/2 ounces of paste pigment representing one gallon of vehicle to one hundred pounds of lead. A complete report of the reductions, spreading rates, etc., used in the tests would take up three or four hundred pages of printed matter. The reductions shown on the following formulas are, however, fairly representative of the reductions used on the combination and single pigment paints. REDUCTIONS ON FORMULA NO. 2 _White and Yellow_ 1st Coat Condition when opened--good. Consistency when broken up--heavy. Reduction recommended by manufacturer--none. Reduction used--3 pints raw oil, 1 pint turps, 1 gallon paint. Consistency after reducing--good, stiff. Working--fair. Drying--fair on pines; cypress--poor. Penetration, pines--good; cypress--poor. 2nd Coat Consistency when broken up--heavy. Reduction used--1-1/2 pints turpentine, 1 pint boiled oil. Consistency after reducing--good. Working--good. Hiding--medium. Drying on pines--good; cypress--poor. One-half pint japan added to gallon of paint. Penetration--fair. 3rd Coat Reduction used--1-1/2 pints oil, 1/2 pint turpentine. _Reductions for Lead Pastes_ Calculated on 100 lb. keg. Formulas Nos. 37-38. (Corroded White Lead.) 1st Coat 6-1/2 gallons oil, 1/2 gallon turpentine, 1 pint turpentine japan. 2nd Coat 3-1/2 gallons oil, 1 gallon turpentine, 1 pint japan. 3rd Coat 3 gallons oil, 1 pint turpentine, 1/2 pint japan. =Hiding Power of Paints.= When the priming coat had thoroughly dried on each panel, the painter carefully stencilled a black Geneva cross over the priming coat with lampblack in oil. The object of this black cross was to make a determination of the comparative opacity or hiding power of the different paints applied. It is well known that various pigments when ground in oil differ in their hiding power in direct proportion to the difference in the refractive indices of the pigments and oils used, those containing high percentages of pigments such as white lead and zinc oxide being superior in hiding power. After the second and third coat of paint had been applied to each panel, there was evident a remarkable difference in the hiding power, as the black cross showed through in some cases quite clearly, while in other cases it was almost completely hidden. The hiding power of a paint is one of the properties which the master painter looks upon as most essential, but it should, of course, be accompanied in a satisfactory paint by good spreading power and longevity.