In the 1970s, Ruscha began to experiment further with the materiality of language, using a variety of substances to create his text-based artworks. This experimentation led to the creation of the "Stains" portfolio in 1969, which consisted of seventy-five works on paper, each marked with different materials, ranging from egg yolk, turpentine, beer, salad dressing to gunpowder. This portfolio not only highlighted Ruscha's innovative use of materials but also his interest in the physical presence and the tactile quality of words​ (National Galleries)​.

Ruscha's engagement with typography took on new dimensions during this period. He moved away from the rigid, hard-edge painting of words towards something more fluid and ambiguous. This shift is evident in works where words appear to have been poured rather than painted, reflecting Ruscha's self-described "romance with liquids." This approach allowed him to create his own typography, where the form of each letter was determined by the behavior of the liquid medium, a significant departure from conventional lettering styles​ (Artspace)​.

Moreover, Ruscha's text paintings from the 1970s often featured phrases, thoughts, and complete sentences, expanding beyond the single words that dominated his earlier works. These phrases sometimes emerged from Ruscha's personal observations, found materials, or his dreams, reflecting a wide array of inspirations. This period also saw Ruscha utilizing unusual backgrounds for his text, such as taffeta, silk, and moire, enhancing the interplay between the textual content and its material substrate​ (Artspace)​.

Ruscha's work during this decade continued to blur the lines between text and image, pushing the boundaries of both painting and conceptual art. His use of text as both subject and object, combined with his innovative use of materials, underscored the transformative potential of words in visual art. Through his explorations, Ruscha not only expanded the conceptual scope of his own work but also contributed significantly to the broader discourse on the relationship between language and imagery in contemporary art.