Scientific American 10, 4.9.1869
The following is a test now adopted by many dealers for testing the covering powers of white pigments "Fine, buff Manilla wrapping-paper, stretched on frames of wood, is painted with best coach black, and varnished until the surface presents a glassy smoothness. To cover and conceal this shining black surface, and present a white surface, is the object of the test; the utmost care being taken all through to note tho exact number of grains, by weight, of material used in each and every coat. No turpentine is used in the painting, the paints being thinned with linseed oil to a proper con-sistency for spreading evenly under the brush. The first coat is applied to the whole surface of the paper; the second to a fraction more than three fourths of the sheet, a portion being left in every case, whereby to compare the effects produced by the successive coats."
"It will be understood that a separate sheet is used for each brand. Size about two and one eighth square feet."
Ei kommentteja :
Lähetä kommentti