2 BULLETIN 1185, U. S. DEPARTMENT OF AGRICULTURE. 
fibers will be seriously weakened through the dissolution of the @ 
pectin or gum that holds together the fiber cells forming the strands — ! 
or commercial fibers. 3 
Many practical retters assert that the only reliable test for the 
completion of retting is to remove several handfuls from different 
parts of the retting tank and examine the quality of the fiber after 
it is dried. Many retters depend upon the Belgian or loose-core 
test made on wet stems freshly removed from the retting tank; in — 
this case retting is said to be complete when the wooden core may 
be pulled out from the fibrous cylinder without any resistance to | 
the pull. The objection to the first or dry-straw method is that 
fiber may be injured by artificial drying unless proper humidity is 
maintained in the drying room. It is impracticable to have to wait 
for the sample to dry naturally in the sun on account of the danger 
of overretting with the remainder of the flax stems in the retting 
tank, and it is rather expensive to equip a drying room so as to 
maintain proper humidity. The second method, that of the loose- 
core test, is very undependable in inexperienced hands and _ not 
entirely dependable in the hands of experienced retters. A positive 
loose-core test indicating that retting 1s complete may at times be 
obtained when retting is far from complete and when the fibers are 
still firmly attached to the rest of the cortex. The study reported | | 
in this bulletin was undertaken to determine whether there existed 
a relation between the flax-stem anatomy and retting that would 
be helpful in testing wet flax stems for the completion of retting 
more accurately than can be done through the use of the loose-core 
test. 
THE RETTING OBJECTIVE AND SOME FACTORS THAT MAY 
INTERFERE. 
The object of retting is to obtain perfect fiber and to terminate 
the process so that the best balance of softness and strength of fiber 
results. Flax fiber, in general, is graded according to strength, fine- 
ness, weight, length, color, and freedom from shives, or pieces of the 
wooden core. The best quality of flax fiber is strong, very fine in 
diameter, soft, feels heavy to the hand, averages 20 inches or more 
in length, and is entirely free from shives. Light-cream and silvery- 
gray colors are common with good flax fiber, but the color is not so 
important as the other qualities. A silken luster is considered de- 
sirable, as this indicates that the fiber is well retted. If the flax 
stems are underretted the fiber is apt to be green in color, due to 
adherent chlorophyll from the cambium layer, and the fibers may 
not be separated from the rest of the cortex. Overretted flax fiber is 
enerally dull gray, lacking in luster, and so very weak that it may 
Be pulled to pieces by the hands with little effort. . 
After the retting process is completed the flax stems are dried 
and the mechanical separation of the wooden core from the retted 
fiber is performed by the breaking and scutching processes. In | 
breaking, the flax stems are run through a series of corrugated 
rollers. This breaks up the wooden core into short pieces known as 
shives. Well-retted flax fiber is soft, strong, and pliable, so that 
it bends between the corrugations of the rollers without breaking 
pA Boe ered 
Liladistese nding 
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