The very important step in preparing cigar tobacco immediately following the harvest. Freshly harvested tobacco leaves (which have been either primed or stalk-cut) are hung in tobacco curing barns, also known as casas de tabacos. There the leaves turn from green to brown in a process known as curing. Moisture is slowly removed from the plant over a period of around 45 days, depending on the weather. Vents are opened and closed in these barns to make adjustments, and sometimes propane gas powered burners or small charcoal (or carbone) fires are lit to increase temperature, and on occasion humidity is added. The tobacco leaves turn from green, to yellow, then finally to brown. The veins and the very thick stem are the last to turn. This curing process prepares the leaves for fermentation, but the tobacco would be too raw and harsh to enjoyably smoke in this form.