The design of the architectural scrim which surrounds the building was changed in September 2012.
 The proposed building itself was a box-like structure.
The three-part corona of the building's design was created by a structure only minimally attached to the building.
The exterior of this structure, whose frames lean outward to create the corona, consisted of a thin screen or "scrim" perforated by geometrical patterns based on historic iron grilles found in African-American communities in Charleston, South Carolina, and New Orleans, Louisiana.
The original design proposed that the scrim be made of bronze, which would have made the museum the only one on the National Mall whose exterior was not made of limestone or marble.
Cost issues forced the architects to change this to bronze-painted aluminum in September 2012.
The change was approved by the Commission of Fine Arts, but the commissioners criticized the change for lacking the warm, reflective qualities of bronze.
Noted architect Witold Rybczynski also criticized the change: "The appeal of bronze is its warm golden sheen and the rich patina that it acquires over time, but uniformly painted surfaces lack these attributes, and over time they don't age, they merely flake. ...
At the time of this writing, the African American museum risks compromising its original intention.
 In architecture, beauty sometimes really is only skin-deep."

The Smithsonian then radically changed the landscaping of the under-construction museum in summer 2013.
The original design for the museum planned a wetland with flowing creek, bridges, and native plants in this area.
But cost considerations led the agency to completely eliminate it.
At first, the Smithsonian proposed a low hedge.
It brought this design to the Commission of Fine Arts in April 2013, which rejected it.
 The Commission expressed "great concern about the possible loss of the symbolic meaning that had been skillfully woven into the design of both the landscape and the building".
In July, the Smithsonian replaced the hedge with a low dull black granite wall.
 The Commission of Fine Arts approved that redesign, and the Smithsonian brought it to the National Capital Planning Commission.
 As of August 2013, the NCPC was anticipated to approve it.

Debate over the corona's finish continued into 2014 before being resolved.
The Commission of Fine Arts repeatedly urged the architects to use bronze for the scrim, as it created a "shimmering, lustrous effect under many lighting conditions" and "conveyed dignity, permanence and beauty".
Duranar paint was the first substitute proposed by the architects, but the commission members rejected it, noting that it had a "putty-like appearance under overcast conditions" and visually fell "far short of the beautiful poetic intention promised by the concept design".
A second finish, the sprayable metal LuminOre, was rejected by the commission because it was difficult to produce in the high quality needed, and was prone to flaking and discoloration.
Electroless plating and anodized aluminum were rejected because they lacked durability.
A physical vapor deposition process involving a nickel-chrome plating was dismissed for not achieving the right color, luster, or warmth.
In early 2014, tests were made with polyvinyl difluoride (PVDF).
This coating was approved by the Commission of Fine Arts on February 20, 2014, and by the National Capital Planning Commission in April 2014.
The design of the architectural scrim which surrounds the building was changed in September 2012.  The proposed building itself was a box-like structure. The three-part corona of the building's design was created by a structure only minimally attached to the building. The exterior of this structure, whose frames lean outward to create the corona, consisted of a thin screen or "scrim" perforated by geometrical patterns based on historic iron grilles found in African-American communities in Charleston, South Carolina, and New Orleans, Louisiana. The original design proposed that the scrim be made of bronze, which would have made the museum the only one on the National Mall whose exterior was not made of limestone or marble. Cost issues forced the architects to change this to bronze-painted aluminum in September 2012. The change was approved by the Commission of Fine Arts, but the commissioners criticized the change for lacking the warm, reflective qualities of bronze. Noted architect Witold Rybczynski also criticized the change: "The appeal of bronze is its warm golden sheen and the rich patina that it acquires over time, but uniformly painted surfaces lack these attributes, and over time they don't age, they merely flake. ... At the time of this writing, the African American museum risks compromising its original intention.  In architecture, beauty sometimes really is only skin-deep."
The Smithsonian then radically changed the landscaping of the under-construction museum in summer 2013. The original design for the museum planned a wetland with flowing creek, bridges, and native plants in this area. But cost considerations led the agency to completely eliminate it. At first, the Smithsonian proposed a low hedge. It brought this design to the Commission of Fine Arts in April 2013, which rejected it.  The Commission expressed "great concern about the possible loss of the symbolic meaning that had been skillfully woven into the design of both the landscape and the building". In July, the Smithsonian replaced the hedge with a low dull black granite wall.  The Commission of Fine Arts approved that redesign, and the Smithsonian brought it to the National Capital Planning Commission.  As of August 2013, the NCPC was anticipated to approve it.
Debate over the corona's finish continued into 2014 before being resolved. The Commission of Fine Arts repeatedly urged the architects to use bronze for the scrim, as it created a "shimmering, lustrous effect under many lighting conditions" and "conveyed dignity, permanence and beauty". Duranar paint was the first substitute proposed by the architects, but the commission members rejected it, noting that it had a "putty-like appearance under overcast conditions" and visually fell "far short of the beautiful poetic intention promised by the concept design". A second finish, the sprayable metal LuminOre, was rejected by the commission because it was difficult to produce in the high quality needed, and was prone to flaking and discoloration. Electroless plating and anodized aluminum were rejected because they lacked durability. A physical vapor deposition process involving a nickel-chrome plating was dismissed for not achieving the right color, luster, or warmth. In early 2014, tests were made with polyvinyl difluoride (PVDF). This coating was approved by the Commission of Fine Arts on February 20, 2014, and by the National Capital Planning Commission in April 2014.
National Museum of African American History and Culture