In contrast to its concrete exterior, with its imposing, monumental façade, the interior of Unity Temple is light and airy. The textured plaster and surface finishes were designed to have a subtle, luminous appearance, embodying the quality of sacred space. The wood trim and the muted earth tones reflect the presence of nature, its order, calm and simplicity.

The original finishes used by Frank Lloyd Wright at Unity Temple were integral to understanding his design concepts. Original specifications indicate that the plaster interior was to be composed of a lime cement plaster, with crushed flint or torpedo sand aggregate, and hair fibers, “[g]oat or long cattle hair or Vanilla fibre to be well beaten, soaked and thoroughly mixed into lime paste…” The plaster was to receive a “rough finish floated evenly with a soft felt or cork faced trowel.” Tests in 1984 and 1987 showed the majority of the painted finishes were washes or lightly applied coatings, appearing ephemeral, revealing the color and texture of the plaster.

In many locations the finishes were applied in a decorative manner, using stippling or wiping off the paint finish – not applied in a uniform layer. The decorative technique, combined with what is now known about plaster composition and appearance, would have created a dynamic interplay among plaster textures, exposed aggregate and mottled paint finishes. Designed and constructed during the height of Wright’s Prairie School period, the overall effect of the interior finishes made his definition of space a powerful feature of this early modern building, and contributed to the profound influence Unity Temple had on the development of modern architecture.

Over time, many plaster repairs have covered or compromised the original textured plaster. Similarly, original finishes have been over-painted numerous times and, most recently, modern latex paints were used that completely altered the appearance of the surfaces. As a result, the interior space no longer reflects Wright’s design aesthetic and the effect of experiencing the space has been substantially altered.

Restoring the finishes to their original appearance was essential to the restoration of Unity Temple: recreating the organic interplay between the building’s structural and interior elements. The restoration project team presented conservation options that included removing all over-painting and applying replicated authentic finishes; applying a new layer of plaster with replicated finishes; and new over-painting on all existing surfaces in a way that closely resembles original treatments.