From 1919, Grabar directed his commission into documenting and preserving Orthodox church murals and icons. The first 1919 expedition to Yaroslavl located and restored previously unknown works of the 12th and 13th centuries. Restorers Fyodor Modorov, Grigory Chirikov and photographer A. V. Lyadov continued studies of northern church art throughout the 1920s and by 1926 produced the first comprehensive study of icons and an assessment of wooden churches that housed them. Grabar's icon restoration workshop became internationally known; Alfred H. Barr, Jr. who visited Moscow in 1927–1928, wrote of Grabar's technology "with great enthusiasm". "It is to Grabar, more than to any other single scholar, that Russia owes the rediscovery of his icons."