In a career spanning more than four decades he produced roughly 370 stained glass commissions for places of worship, hospitals, universities and private residences throughout the United States.
Around this time, the death of his mother prompted him to return to Germany where he viewed many works by Georg Meistermann and Ludwig Schaffrath and reestablished contact with the Düsseldorf art scene.
Over the next decade Spahn worked with George Winterowd and the nationally recognized church architect Ed Sovik to produce 75 commissions around the country totaling more than 400 stained glass windows.
Around this time he also met Frank Kacmarcik, a monk at St. John's Abbey in Collegeville, Minnesota, and nationally recognized liturgical and architectural consultant.
Spahn served as a guest lecturer at St. John's University about stained glass and sacred art in the contemporary church environment.
In 1988 Spahn interrupted his painting for over two years to focus on several major projects in stained glass, including the library window for St. Thomas University.
The next decade saw the production of a series of paintings which departed from traditional techniques of representation, as well as a number of large stained glass projects and commissions for liturgical design and consulting.