《天工开物·中篇·陶埏》
炼泥造砖，也需要先挖取地下黏土，对泥土的成色加以鉴别。黏土一般有蓝、白、红、黄几种颜色，以黏而不散，土质细而没有沙的最为适宜。
凡埏泥造砖，亦掘地验辨土色，或蓝或白，或红或黄，皆以粘而不散、粉而不沙者为上。
Making bricks from clay also requires digging of underground clay and identification of the color of the clay. The clay is generally blue, white, red, and yellow in color, and the most suitable is the one that is sticky but not loose, and is fine-textured without sand.