12 BULLETIN 229, U. S. DEPARTMENT OF AGRICULTURE. 
Frequency of chipping. — Table 8 shows the rate with which the 
gum flows. 
Table 8. — Rate of exudation of gum from " chipped' ' long leaf pine. 
Day. 
Grams of ! Total ex- 
gum. | udation. 
Day. 
Grams of 
gum. 
Total ex- 
udation. 
First 
113. 
22.5 
13. 5 
9.0 
C 1 ) 
Per cent. 
67.26 
13. 39 
8.04 
5. 36 
Fifth and sixth 
9.0 
Per cent. 
5.36 
Second 
Third 
Seventh 
Total 
1.0 
0.59 
Fourth 
Fifth .. , 
2 ir}g. o 
100.00 
No weighing. 
2 168 grams equal 0.37 pound. 
It is seen that 88 per cent of the total flow occurs during the first 
three days. As the resin ducts become plugged with coagulated or 
crystallized gum the flow gradually ceases, and the gum thereafter 
produced is stored in the resin ducts until the ends are again opened. 
When the ducts immediately above the wound become full, the resin 
tends to diffuse or soak into the wood further removed from the bark 
This diffused resin does not drain out when the tree is wounded, and 
for this reason chipping should be done often enough to insure that 
the active ducts immediately beneath the bark and above the wound 
will not remain full of gum. On the other hand time should be al- 
lowed between drippings for a new supply of gum to form. In prac- 
tice, trees are chipped once a week. It is possible that more frequent 
chipping would give a greater yield of gum for a short period (one or 
two years), but at the same time it might further reduce the vitality 
of the tree and so result in a smaller total yield over a longer period. 
The increased yield, moreover, must be enough to justify the addi- 
tional expense. Experiments are needed to show how the rate of 
flow is affected by frequency of chipping in operations extending over 
different periods of years. 
Size and number of faces. — The scar on the tree caused by successive 
chippings is usually about 14 inches wide, and is known as the "face." 
Wounding the tree, of course, diminishes its vitality by interfering 
with the transmission of water from the roots to the leaves and of 
nutritive matter from the leaves to the roots. When a small tree, 
8 or 10 inches in diameter, is chipped, it usually either dies outright 
or its further growth is greatly retarded, even though the width of 
the face is kept at the minimum. 
PRINCIPLES UNDERLYING THE DISTILLATION OF CRUDE GUM. 
The crude gum was formerly distilled without the addition of 
water; in consequence the quality of the resulting turpentine and 
rosin was poor. The yield of turpentine was very low, but it was 
impossible to increase it without coloring the liquid yellow with the 
