Opaque to transparent : insights on Bloom, Haze, Protrusions and “Ground Staining” from the Hudson River School and the church archive

Degradative phenomena in oil paintings on canvas are prevalent in the paintings of the Hudson River School. Visual manifestations of these conditions vary. Bloom, haziness and variable translucency are often misunderstood as part of the intended design. The difficulties of interpreting changed visual information and treating these changes are considered. Damaging historical treatments are briefly reviewed. Examples of various conditions are illustrated in paintings by Frederic Church and Hudson River School painters. Research carried out by the Molecular Paintings Research Group on samples from the archive at Olana reveals the mechanism for understanding bloom, haze, protrusions and variable translucency. Their findings are discussed. Oil sketches from the Church archive provide additional information. One particular sketch shows protrusions and bloom visible in a distinct pattern suggesting a brush application of an unknown substance. Archival materials from Olana State Historic Site, including letters, receipts and books, support lead acetate as the probable cause. Areas for future study are suggested.