Trailers can be used to handle overflow cotton while a module is being completed. Cotton tarps permit moisture vapor to pass through the tarp and, therefore, are less likely to have condensation form due to the daily heating and cooling of the cotton's surface. Cotton tarp's finished dimensions should be six feet wider than the module builder and eight feet longer to cover adequately the top edges of the module and to allow for shrinkage. If a module is properly packed, the sides shed water, and the module requires no additional protection. After an hour, if the tarp passes more than one drop per minute, the tarp should be rewater-proofed before using.
Synthetic tarps are lighter, less costly, and generally more durable than are cotton tarps.
Economics alone justifies the use of synthetic tarps. However, since they permit less moisture vapor to pass through, some precautions must be taken with synthetic tarps to prevent seed cotton quality losses from occurring. When ordering synthetic tarps, specify adequate ultraviolet light inhibitor to protect the tarp for two or more seasons or 180 days of exposure. Inspect tarps during use and before reuse for deterioration. Specks of tarp material flying off or on the surface of a module are good indications that the ultraviolet light inhibitor was not adequate.