What I recall: 

-Children’s picture book, read in the 90s, but could be from 60s/70s/80s

– Illustratons were very simple, like James Stevenson or Jules Pfieffer

– Plot about a boy who visits some sort of factory or construction site where words are made- very similar to Charlie and the chocolate factory, but with concepts around stuff like words (and maybe some numbers/math too?)

– I recall a section where a kid gets stuck to a balloon (maybe a speech bubble) and floats away, and has to be rescued by an older gentleman who throws some sort of dart to deflate it. The man runs? The factory and gives the boy a tour.