Sentence:  To reinforce , and sometimes to replace , the simulated typography , Braque and Picasso began to mix sand and other foreign substances with their <WSD>paint</WSD> ; the granular texture thus created likewise called attention to the reality of the surface and was effective over much larger areas . 
Meaning of the word marked with <WSD> tags:  a substance used as a coating to protect or decorate a surface (especially a mixture of pigment suspended in a liquid); dries to form a hard coating