This section is from the book "The National Capitol. Its Architecture Art And History", by George C. Hazelton, Jr. Also available from Amazon: The National Capitol Its Architecture Art and History.
The corridors are noticeable for their decorations in fresco, oils and " lime." Much of the beauty of these is lost, however, to appreciative eyes because of the bad lighting. Most of them were painted in the summer months; for the Senators and Representatives strenuously objected to the presence of scaffolding in the building during sessions. A corps of artists assisted Brumidi in the execution. Each was employed for his excellence in a particular branch of art. One painted scroll-work only ; another devoted himself to animal painting, another to birds, another to flowers, and still another to landscapes. Some bits in oil, notably all the birds and small insects, are attributed to Leslie, an American painter. Brumidi himself painted all the figures, heads and groups, besides directing and overseeing the entire work. Nothing was done except by his approval, and all the designs, in drawing as well as color, were of his making. In these, Brumidi deserves praise for his- use of animals. They have too long been neglected in the decorative arts, furnishing, as they do, such exquisite expressions of life—that one element necessary to the good and beautiful in all human effort as it is in Divine.
The decorations of the ceilings of some of the committee rooms are distemper. Unlike in fresco, the plaster is dry when the colors are applied. These are ground to powder and mixed with water and glue to make them adhere to the wall. Unlike in fresco, too, it is not necessary for the artist to restrict himself to the use of mineral colors; the range of the palette is the same as in oils.
Many of the walls have been much marred by being scrubbed with sand soap; but, fortunately, the scrubbers have not been so solicitous for the cleanliness of Uncle Sam's property as to extend their efforts far above the easy reach of the arm. All things have their use, and this natural antipathy of some of the colored brethren to extended labors has undoubtedly been a blessing to the art of the Capitol, and saved much of the painting on the upper walls and ceilings unimpaired. Alas, for that within reach ! These decorations should be simply dusted, and otherwise untouched, if they are to be preserved.