If installers overfill the stud cavities and close the application holes too early before Icynene foam fully expands and escapes, the foam might exert pressure on the wall as a way of looking for an escape route. As such, Icynene causes the wall to bulge out.
After the installers have removed the excess Icynene, there still remains a thin film that can be removed by sanding it down several days later. However, if the installers make the mistake of painting on the thin film, that changes the film’s color but does not hide it. Another problem is that using Icynene for thick wall cavities is expensive.