Although the mechanisms of in-mold events such as stickers, flux entrapments, and corner bleeders have been well established and documented, there has been a lack of understanding concerning how the copper thickness affects the frequency of these events. As the casters continue to push the boundaries of machine design, the copper molds are exposed to higher numbers of heats per campaign and more campaigns per copper set. This results in thinner coppers on both the broad faces and narrow faces of the mold as refurbished coppers continue to be extensively used. Although the copper alloys and mold coatings developed have some effect on heat transfer the amount of copper lost during refurbishment also has a significant impact on the amount of heat extracted through the water-cooled copper mold and on mold flux performance. In this investigation, the effect of copper thickness on the frequency of in-mold events such as stickers, flux entrapments, and corner bleeders has been studied at United States Steel Corporation ("U. S. Steel") with respect to steel grade type and mold flux.