Rock (geology) arkoses (12%). Sedimentary rocks often contain fossils. Sedimentary rocks form under the influence of gravity and typically are deposited in horizontal or near horizontal layers or strata and may be referred to as stratified rocks. A small fraction of sedimentary rocks deposited on steep slopes will show cross bedding where one layer stops abruptly along an interface where another layer eroded the first as it was laid atop the first. Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which the original rock was
Heat press technology in newer machines enables precise control of heat and pressure levels and timing. The most common types of heat press employ a flat platen to apply heat and pressure to the substrate. In the "clamshell" design, the upper heat element in the press opens like a clamshell, while in the "swing-away" design, the heat platen swings away from the lower platen. Another design type a "draw style press" allows for the bottom platen to be pulled out like a drawer away from the heat for preparation of the graphic. Vacuum presses utilize air pressure to provide the necessary force