A few days too long in the field may make the difference between retting and rotting. Therefore, it is most important that inexperienced farmers obtain the assistance of the hemp-mill superintendent or an experienced grower in determining when to stop the retting.
Dry hemp stalks should be tested when possible to determine the degree of retting. Three to six stalks are taken in both hands and bent back and forth to perform the break test. If properly retted, the fiber should not break when the woody core breaks. The hurds should fall free of the fiber in the breaking and shaking between one's hands. If the hemp is only partly retted, some hurds will adhere to the loosened fiber. Unretted hemp fiber is usually green or light yellow. Dew-retted hemp is usually slate gray or black.
After the fiber is broken free, its strength should be tested by breaking a small strand between the fingers. A small strand of fiber not twisted and about 3/32 inch wide should break with great difficulty and with a decided snap. If it is very weak and breaks with little or no snap the hemp is probably badly overretted or may have been grown under unfavorable cultural conditions. (See [p. 5].)
All indication that the retting end point is near is that the hemp makes "bowstrings." In a small percentage of the stems, less than 1 to 5 percent under certain conditions, the middle of the stalks appears to ret first. The fiber comes free from the middle and forms a string fastened at the top and bottom of the stem, not unlike a bowstring. If bowstring stems are found, a sample of the hemp should be taken to the hemp-mill superintendent as soon as possible for verification of the retting end point. The bowstring condition is only a supplementary aid in determining when to stop the retting, and it may or may not occur in properly dew-retted hemp.
Some experienced hemp producers use the peeling test for determining the degree of retting. This is accomplished by peeling the fiber away from the butt ends of the stems. If properly retted, the fiber should peel freely from the woody core of the stem. If the hemp is not sufficiently retted, the fiber will break after a few inches have been peeled. This free-peeling stage is desirable for breaking hemp on hand breaks. Where hemp is to be processed by machinery the retting need not progress quite so far as is necessary for hand breaking.
Picking Up the Retted Stalks
Hemp stalks may be picked up by hand. This method has been used from early times and is satisfactory where labor is plentiful. However, in this country it is being replaced by machine pick-up binders.