I,
Seasoning and Machining Degrade in Young-growth
Douglas-fir Dimension Lumber
By
B. G. Anderson
A. C. Knauss
R. G. Frashour
Reporf No. D-1
May 1954
OREGON FOREST PRODUCTS LABORATORY
State Board of Forestry and School of Forestry,
Oregon State College, Cooperating
Corvallis
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS
S1J1'14ARY
1
.
INTRODUCTION
STUDY ChARGES .
.
8
.
10
10
RESULTS AND DISCUSSION
Degrade
Black-knotted pieces
.
.
Shipping weight.
Specific gravity and ring count.
.
Drying rate-kiln schedules
.
N
5
.
.
.
.
.
12
13
.
.
.
.
.
.
. ........... .
13
.
14
.
.
.
Greenmoisturecontent........
Uniformity of final moisture èonterit
Moisture-meter readirig
Shrinkage during kiln-drying . . . .
Residu.1 shrinkage
.
.
.
.
.
.
.
.......14
14
.
.
.
.
.
.
.
.
.
.
.
.
.
.
15
15
15
CONCLUSIONS
16
REI'4APJcS
17
BIBLIOGBAPRY
18
TABLES
Total Degrade in No. 1 and 2 Common Young-growth Douglas-fir
Dimension Lumber
19
Kiln-dried S4S Recovery in Grade from No. 1 Ccnnnon Younggrowth Douglas-fir Dimension Lumber
20
Kiln-dried 54S Recovery in Grade from No. 2 Conm-ion Younggrowth Douglas-fir Dimeision Lumber
21
Table 4,
Effects of Low EMC Step in Schedule on Degrade Percentages
22
Table 5.
Effects of Low
of Degrade
Table 1.
Table 2.
Table 3.
Table 6.
4C Step in Schedule on Various Causes
23
Effects of Final Average Kiln-dried Moisture Content on
Degiade Percentages
2
IISUOR
3/00 30805-200
JLE
24
Page
Table 7.
Table 8.
Effects of final Average Kiln-dried Moisture Content on
Various Causes of Degrade
Effects of Initial Dry-bulb Temperature on Degrade
Percentages.
.
.
.
Table 9,
.
.
.
.
.
.
Table 11.
.
.
.
.
.
.
.
.
26
ffe cts of Initial Dry-bulb Temperature on Various Causes
....,..... 27
ofDegrade
Table 10.
.
25
Effects of Low ENC Step in Schedule on Doflar Recovery per
Thousand Board Feet of Kiln-dried Dimension Lumber
28
Percentages of Green Pieces Containing Black Knots of Over
3/4-inch Diameter
29
FIGURES
Figure 1.
Relationship of Shipping Weght to Average MOICtUT?
Content
Figure 2.
Relationship of Rough Weight to Average Mo4.sture Contei't,
Figure 3.
Cumulative Distribution of Green Density Values.
Figure 4.
Cumulative Distribution of Specific Gravity Values.
Figure 5-15. Photographs of End-grain Kiln Samples.
Figures 16-22. Photographs of Knot
Condition;
Charges 3 through 9.
Figures 23-32. Drying Rate and Kiln Schedule Charts; Charges 2 through 10.
Figure 33.
Cumulative Distribution of Green Moisture Contents.
Figures 34-43. Cumulative Distribution of Moisture Meter Readings:
through 10.
Charges 2
Figure 44.
Moisture Meter Readings Compared with Oven-test Moisture Content
Values.
Figure 45.
Cumulative Distribution of Green and Kiln-dried Thickness Values.
Pigure 46,
Cumulative Distribution of Shrinkage Values During Kiln-drying.
Figure 47.
Average Residual Shrinkage Values.
Figure 48.
Cumulative Distribution of Residual Shrinkage Values.
igure 49.
End Grain View of 343
Dimension: Charges 4 and 5A.
Figure 50.
End Grain View of 345 Dimension: Charges 6
Figure 51.
End Grain View of 34$
Dimersion:
Charge 8.
Grain View of $43
Dimension:
Charge 9.
'igure 52.
End
and 7.
ACKNOWLEDGNTS
The authors express their sincere appreciation for the great amount of
assistance and àervice extended by the f'oUowing persons and organizations:
S. Brown and A. D.
Johztson, of the West Coast Bureau of Lumber Grades
and Inspection, for grading service on all the lumber used in the study.
Don Johnson,
Alberteon Lumber Company, Philornath, and C, R. Bayless,
Bayless Lumber Company, Philomath, who furnished about 52 M board feet of lumber for the study.
Ted Huntley, Corvallis Lumber Company, who furnished planing and storage
facilities for a large percentage of the lumber used in the study.
R. Clark and C. W. Crenshaw, Clear Lumber Sales Company, Lebanon, who
furnished lumber and planing facilities for one study charge.
W. G. Hanley and Gene Durlam, Douglas Fir Products Company, Lebanon, who
furnished lumber, dry-kiln facilities and planing facilities for one study charge.
Oscar Meland and Robert Short, Timber Structures, Inc., Portland, who
furnished lumber, dry-kiln facilities and planing facilities for one study charge.
Raymond 1eitz and Elmer Matson, U. S. Forest Service, for constructive
suggestions.
Robert Eby, West Coast Lumbermen's Association, Portland,
H.
'. Jefferson, Nettleton Lumber Company, Seattle,
T.E. Heppenstal, Long-Bell Lumber Company, Lougview, and
H. E. Morgan, Weyerhaeuser Lumber Company, Longview,
for their constructive suggestions and discusàion during the planning of this
project.
0. R. Randall, of the Laboratory ataff, for assisting in the experimental
work and drawing of the graphs.
SUMMARY
The increasing volume of young-growth Douglas-fir timber cut in the
Pacific Northwest emphasizes the need for more knowledge on the characteristics of lumber sawed from these trees.
The study described here was initiated to learn the extent arid causes
of degrade resulting from kiln-drying young-growth Douglas-fir dimension
lumber.
At the same time it was possible to determine the degree of shrink-
age during and after kiln-drying, and to check the final shipping weights
of the lumber after drying.
Degrade was measured in ten kiln charges of approximately 6500 ftn
(feet board measure) each, of 2- by 8-inch by 16-foot young-growth Douglasfir dimension lumber which were kiln-dried and surfaced to 1-5/8 by 7-1/2
inches.
An additional charge was surfaced green to determine the change
in grade caused by machining alone.
Neither the average final moisture content to which the charges were
dried (approximate range 12-18 per cent) nor the temperatures used in drying
the charges seemed to have an appreciable effect on the amount of degrade.
The anount of degrade was greater, however, when a low EMC* level was main-
tained during the schedule, as shown by the following table:
* Equilibrium moisture content; the moisture content which wood will
attain after long exposure to given aimospheric conditions.
--
ENC of
low humLdity
step (range)
Average total
basis)'
No. 1 Common
No. 2 Comon
degradeJ
Per cent
3.3-4.4
Per cent
Shake & grain
separation
Loose knots &
edge knots
Planer split
and warp
Season checks
Knotholes
0.7
0.6
1.9
0.4
5.7
1.4
3.2
3.8
0.2
1,0
6.0
Tpta].
7 7-U .0
Shake & grain
separation
Loose knots &
edge knots
Planer split
and warp
Season checks
Knotholes
Total
1
Per cent
0.7
0.8
1.9
0.7
1.2
0.0
2.1
1.1
0.1
0.5
5.9
3.2
Degrade from shrinkage (skips in dressing) is not included.
Total degrade in the Select Structural grade was consistently higher
than degrade in No
10 (Number 1 Common).
The amount of lumber in the select
structural grade, however, was too small for full analysis.
Although young-growth Douglas-fir lumber is relatively free from the
black knots found characteristica11y in old-growth, an average of 18 per
cent of the green pieces in both No. 10 and No. 20 contained black knots
over 3/4 inches in diameter.
Despite this fact, the average degrade from
knot damage including knotholes
was only about 4 1/2 per cent in No. 10
and about 1 1/3 per cent in No. 2C.
Some of the knotholee
that developed
during seasoning o' machining were too small to lower the original grade.
The pieces containing these small knotholes averaged 2.9 per cent in
No. 10 and 5.5 per cent in No. 20.
-3-
Degrade from planer split and warp in lumber dried using a high
minimum ENC step in the kiln schedule averaged 1.2 per cent in No. 10 and
1.1 per cent in No. 20.
Using a low minimum EMC step in the schedule led
to an average degrade from planer split and warp of 5.7 per cent in No. 1C
and 3.8 per cent in No. 20.
Prices received at the mill are usually higher for kiln-dried than
for green dimension lumber,
Not all of this premium is gained by the mill,
however, because of the drop in grade of some pieces during drying and
machining.
Miii prices1
Green
Kiln-dried
Grade
Se]. Str
No. 10
No 20
A summary of these factors is shown below.
$78.50
68.50
65.25
$92.00
82.00
76.00
Recovery value of
kiln-dried lumber_
Low EMC
High EMC
$88.24
79.66
74.19
Loss from degrade
Low EMC
High ENC
$89 .81
$3 .76
81.30
75.13
2.34
1.81
$2.19
0 70
0.87
Prices per N fbm based on Crow's Price Reporter, 20 August 1953.
Average of "Most Sales." A price differential of $10.00 is assumed
between Select Structural and No. 10.
Average shrinkage in thickness and width during kiln-drying to 12 per
cent average moisture content was 3.5 per cent, with 80 per cent of the pieces
shrinking 4.1 per cent or less.
When lumber which had been kiln-dried to 18 per cent average moisture
content and surfaced was allowed to dry further to about 12 per cent moisture content, the average additional shrinkage was found to be about 0.9
per cent, with 90 per cent of the pieces shrinking 1.5 per cent or less.
The average residual shrinkage when dried from 18 to 5 per cent moisture
content was 2.5 per cent.
The shipping weight of S48 green dimension ranged from 2500 to 2800
pounds per thousand board feet.
When kiln-dried to 18 per cent average
moisture content, the surftced lumber averaged 2170 pounds per thousand, and
when dried to 12 per cent moiture content averaged 2O0 pounds per thousand
board feet.
Time required for drying to a final average moisture content of l
per cent ranged from 4
to 90 hours.
Th
shorter interval was reeded for
kiln schedules with a constant dry-bulb temperature of 200 deg F.
Drying time to 12 per cent average moisture content was 110-120 hours.
A general picture of drying times may be gained by comparing charges
2 and 5A with charges 6 and 7.
Dry-bulb
_temperatur_
Charge
2
Initial
)
)135
5A
Final
ENC
Initial
Final
175
16
)
7
/. -22-54
11
)
180
180
12
Avg final
MC
(75
18
(
110
12
(
72
18
120
12
4
)
)
Drying
time
Hours
9
(
(
SEkSONING A.ND NCHINING DEGRADE IN YOUNG-GROWTH
DOUGlAS-FIR DIME1SICN LUMBER
by
B. G. Anderson
Oregon Forest Products Laboratory
A. C. Knauss
Forest Utilization Service
Pacific Northwest Forest Ecperiinent Station
and
R. G. Frashour
Oregon Forest Products LaboratQry
INTRODUCTION
No one seems to know what the annual cut of second-growth, or, more properly, young-growth Douglas-fir, is at present.
But it is known that the propor-
tion of young-growth sawed to the total cut is increasingl yearly in the Douglas-
fir region, and that small sawmills are being built each year to cut small-diameter logs from young stands.
The Douglas-fir lumber industry is beginning the
European countries and
transition from an old-growth to a young-growth economy.
the southern pine region in the United States have made this transition, and
have been confronted with problems quite different from those encountered when
the lumber production was entirely from old-growth timber.
A volume estimate
of staxiding Douglas-.fir timber in Oregon and Washington in 194.5 placed the old-
growth stand at 185 billion fbm and the young-growth stand at 80 billion fbm-defining young growth as under 160 years old.*
As the annual cut of young-growth timber increases, it is inevitable that
more young-growth lumber will be kiln-dried.
Consequently, interest is increas-
ingly maaifested in the problems which wl1 appear as more mills go into the
* Kirk1aid Report fo
the Amerioan Forestry Association, 1945.
production of such lumber.
with a higher cut of thi
One might speculate on seasoning problems to arise
type of lumber, such as:
Small-diameter logs mean greater ring curvature.
Should more
cupping be expected during kiln-drying, and consequently more planer
split during
machining?
Young-growth frequently has ccse grain.
Should ceason checks be
expected, and uore grain separation during machining?
3
Young-growth may have a higher percentage of tight knots than does
old-growth.
Does a possibility exist of drying this tight-knotted
lumber to moisture content levels lower than 18-20 per cent without.
excessive increases in degrade from knot damage?
Ioung-groi4h may contain more abnormal wood than does old-growth.
Will this result in more warp during kiln-drying?
The smaller the
it is found.
og diameter, the higher the percentage of sapwood,
Will this increase the incentive to kiln-dry young-
growth dimension in order to avoid higher green shipping weights?
A higher percentage of sapwood means more susceptibility to stain,
nold, and decay of green lumber during bulk shinent and storage.
Will this provide another incentive for the kiln-drying of younggrowth dimension?
Shrinkage of young-growth Douglas-fir lumber may differ from that of
old-growth.
Will this necessitate an adjustment in width and thickness
of rough-green lumber?
To answer some of these questions the Oregon Forest Products Laboratory,
in cooperation with the Pacific Northwest Forest
and Range
Experiment Station,
the West Coast Lumbermens Assqciation, the West Coast Bureau of Lumber
ades
and Inspection, and several lumber companies located in the Willamette Valley,
-7-
recently completed the initial phase of a long-term investigation into effects
of seasoning and machining young-growth Douglas-fir lumber.
The first part of
this study has been concerned with 2- by 3-inch by 16-foot young-growth Douglasfir dimension lumber, in the grades of Select Structural, No. 1 Common and No. 2
Common.
Most of the Douglas--fir dimension now cut is machined and shipped green.
However, for around 25 years some Douglas-fir mills have been kiln-drying commofl
grades of Douglas-fir in order to preshrink the pieces at least partially and
remove the risk of stain and decay during bulk shipment and storage.
Other
reasons for kiln-drying have been to obtain reductions in shipping weights, and
highei- prices for kiln-dried lumber.
Twenty-seven years ago A. C. Knauss and his co-workers at Vernonia, Oregon,
conducted a study of degrade in kiln-dried old-growth Douglas-fir dimersion.
The
results of this study con.ftrmed a prior conclusion of the Oregon American Lumber
Company that kiln-drying of this type of lumber would be a practical operation.1'2'3
This study established the present practice of kiln-drying dimension to a moisture
content level of 18-20 per cent.
One reason for drying to this level is to limit
the degrade from loss of black or encased knots in old-growth lumber.
As it is
expected that sewer black knots will be found in young-growth, the present study
was so planned as to gain information on degrade at various average moisture
content levels between 12 and 18 per cent, in order to ascertain if tight-knotted
stock could be dried to lower moisture content levels without excessive increase
in degrade from knot damage.
The objectives of this study on seasoning and machining degrade in younggrowth Douglas-fir dimension lumber are, in part, as follows:
1.
To determine the amount and causes of degrade in several grades of
young-growth Douglas-fir dimension lumber resulting from kiln-drying
i.iith various 1dm
schedules to moisture content levels between
12 and 18 per cent.
To obtain shrinkage measurements from green to kiln-dried moisture
content level.
To obtain residual shrinkage from the kiln-dried, surfaced dimension
to that reached in use.
To obtain shipping weights of lumber dried to various moisture content
levels.
To determine the effects of kiln-schedule modifications.
To determine specific gravity and ring count of lumber used in the
study charges.
STUDY CHPRGES
There were eleven study charges, each of approximately 65(X) Ibm.
Charge 1 was planed green to determine the effect on grade of machining
only.
All other charges were kiln-dried before machining as follows:
Schedules and Drying Times for Kiln-dried Cha±ges.
Charge
Location
of kiln
Dry-bulb
temperature
Initial.
Final
Initial
Final
Drying
time
Average
Moisture content
Initial
Final
Hours
2
3
4
5
5A
6
7
8
9
10
D.Fir Prod Co
OEPL
OFPL
Timber Struct.
OFPL
OFPL
OFPL
OFPL
OFPL
OFPL
135
135
134
160
135
180
180
200
200
130
175
180
175
190
175
180
180
200
200
130
17.2
15.9
15.9
14.2
15.9
12.1
4.4
7.8
4.3
3.3
4.3
9.0
8.8
7.7
12l
7.7
7.7
11.0
* Equilibrium moisture content level was
77*
11.0
13.2
75
77
48.9
86
51.6
44.7
188
110
119
117
52
64
90
per cent during
44.6
44.8
48.0
47.8
48.0
40.8
18.4
18.0
14.9
7.8
12.4
12.1
12.5
18.0
17.0
17.9
33.3
last 13 hours.
-9-
The two conmiercial kline used in the study, and the experimental kiln at
the Oregon Forest Products Laboratory, were steam-heated, cross-circulation,
compartmenttype with reversible fans.
The loading on kiln cars of all study
charges was by the unit package system with fork lift.
1 5/8 inches; sticker spacing was
4
feet.
Sticker size was 3/4 by
All the lumber used in the study was
Total length
flat-piled inT4nit packages which varied from 2 to 4 feet in height.
of air travel through the lumber as it was piled on kiln cars was 8 feet.
Air
velocity through the loads of lumber in the kiln was between 350 and 450 feet
Air circulation was reversed apDroxirnately every twelve hours.
per minute.
Charge 1 was planed at Clear Lumber Sales Company, Lebanon.
kiln-dried and planed at Douglas Fir Products Company, Lebanon.
kiln-dried and planed at Timber Structures, Inc., Portland.
Charge 2 was
Charge 5 was
All the rest of the
study charges were kiln-dried at the Oregon Forest Products Laboratory, and planed
at Corvallis Lumber Company, Corvallis.
The lumber for the latter charges was
obtained at the Bayless Sawmill, Philomath, through the courtesy of the Albertsen
Lumber Company, Philomath.
The planer at Corvallis Lumber Company operated at a feed rate of 290 feet
Both the side heads and face heads turned at 3700 revolutions per
per minute.
minute, the side heads with 6 knives and the face heads with 8 knives.
The knives
on the face heads were set at a cutting angle of 28 degrees, the same cutting
angle being used for both green and kiln-dried dimension.
The planer at Douglas Fir Products Company had a 10-knife head turning at
3450 rpm.
The knives were ground with a back-bevel.
Feed rate was 360 feet per
minute, and the knife angle was 27 degrees.
The planer at Timber Structures in Portland had an 8-knife head turning
at 3400 rpm.
beveled.
Top arid side knives were back-beveled; bottom knives were not back-
Feed rate was 250 feet per minute.
Knife angle was 30 degrees.
-10-
AU lumber in the study was planed to American Lumber Standards size of
]. 5/8 inches by 7 1/2 inches.
The lumber used in the study charges was graded three times by inspectors
from the West Coast Bureau of Lumber Grades and Inspection.
The first grading
was done on the rough-green lumber, the second on the rough-dry, and the third
on the surfaced-dry lumber.
Such pertinent data as degrade, final moisture content, drying rates,
rough weights, shipping weights, shrinkage, and specific gravity were kept on
each charge.
RESULTS AND DISCUSSION
Degrade
Charge 1, which was
machined green, showed that no change in grade occurred
between the rough-green and the 54S (surfaced-four-sides) green conditions.
For
this reason all the degrade which developed in the kiln-dried S4S lumber was
charged to seasoning, even though most of such degrade developed during the
machining operation.
Table 1 shows the degrade percentages found
£ or Number 1 Common and Number 2 Common.
in
the kiln-dried 54S charges
The average total degrade found in
Number 1 Common was about twice that found in Number 2 Common, although the ratio
did not hold very consistently within individual charges.
The degrade found in
Select Structural averaged about twice that in Number 1 Common.
Table 2 shows the percentage recovery in S4S grade based on the roughgreen footage of Number 1 Common in individual charges.
for Number 2 Common is presented in Table 3.
The same information
Tables 4 through 9 show the effects of three different variables on the
degrade found in Number 1 and Number 2 Common.
were (1) the lowest
The three variables considered
4C step in the schedule, (2) the average kiln-dried moisture
content of the charge, and (3) the initial dry-bulb temperature in the schedule.
An examination of these data revealed that the lowest
1C step in the schedule
was the only one of the three variables which had an important effect on the
amount of degrade.
When degrade was subdivided according to types of defect it
was seen that degrade because of knot damage was rather constant regardless of
moisture
content
to which the stock was dried or how the dry-bulb temperature
arid EIV1C were manipulated.
In Iumber 1 Common, knot damage was usually the most
Important source of degrade.
Planer split and warp were affected by the lowest
EMC step as well as by the moisture content to which the stock was dried, but
not by the initial dry-bulb temperature.
An examination of Table 4 shows that total degrade in both Number 1 and
2 Common was doubled by use of a low-humidity schedule.
Charges dried with schedules having high initial dry-bulb temperatures
did not have higher degrade percentages than did charges dried with low initial
dry-bulb temperatures (Table 8).
Table 10 presents degrade in terms of dollar value, based on current
prices during the summer of 1953.
The loss from degrade in the low-humidity
schedules was higher than loss in high-humidity schedules by about
fbm for Select Structural,
l.60 for Number 1 Common and
i.60 per M
l.00 for Number 2
Common.
Degrade is a function of EMC and time.
function of
iC and time.
Final moisture content
IS also a
It would be misleading, however, to conclude that
degrade is a function of final average moisture content, because
final average moisture contents
a wide range of
be obtained using iow-humid ty schedules.
-12-
It appeared that the effect of a low
1C schedule on degrade took place much
faster than its effect on average moisture content.
For further information on
this point refer to the section entItled 'Reniarkstt.
Because of the importance of knot damage, a supplementary study was made
to determine the influence of drying temperature on the development
of damage to
tight knots.
Two small matched charges were dried at a constant EMC of 12 per
cent; one of the charges with a constant dry-bulb temperature of 125 deg F, and
the other at 175 deg F.
No difference cOuld be detected In the development of
damage to tight knots as the two charges dried.
An attempt was made in charge 9 to reduce the amount of knot degrade by
steaming the charge before unloading, as well as by wetting down the individual
boards as they were unstiekered.
No noticeable reduction in total degrade was
experienced as a result of this treatment.
However, this charge suffered the
least amount of degrade from planer split and warp of any of the kiln-dried
charges.
No ill effects from the wetting were noted.
Reports of lumber sales showed that in August 1953 kiln-dried Douglas-fir
dimension sold at a premium ranging from $10.75 for No. 2 Common to
13.50 for
Select Structural arid No. J. Common over the same item shipped green. * As the
result of degrade, the dry surfaced lumber failed to fully supply this premium.
Results of this study showed that with properly chosen kiln-drying schedules,
young-growth Douglas-fir dimension could be kiln-dried to a moisture content Of
12 per cent with the degrade reducing, the full premium return by $0.70 for No.
1
Common and
0.87 for No. 2 Common, the principal grades produced at the mill,
Black-knotted pieces
The percentages of pieces within individual charges which contained black
knots c
oier
/4-inch diameter ranged from 10 to 28 per cent (Table 11).
Crow's Price
'August 20, 1953.
Degrade
-13-
from knot damage of all types averaged about 4 1/2 per cent in No, 1C and about
1 1/3 per cent in No. 2C.
Some damage to appearance, however, was caused by knot-
holes which were too small or too few to lower the grade of the piece.
Somewhat
less than 10 per cent of the pieces within individual charges contained knotholes
which affected the appearance but did not lower the grade; the average in all
charges was 2.9 per cent in No, IC and 5e6 per cent in No. 2C.
Shipping weight
Figure 1 shows the relationship of 54S shipping weight to average moisture
content in 2- by S-inch by 16-foot young-growth Douglas-fir dimension.
Approxi-
mately 20 per cent of the pieces in each charge were weighed rough-green, roughdry and surfaced-dry.
individual charges.
Figure 1 is based on the average surfaced-dry weight for
It can be seen that kiln-drying will result in a shipping-
weight saving of from 350 to 650 pounds per N fbm of surfaced dimension lumber,
depending upon the initial green moisture content and the moisture content to
which it is dried.
Figure 2 shows the relationship of weight to moisture content in rough
2- by 8-inch by 16-foot dimension.
The water removal during kiln-drying varied
from 700 to 1000 pounds per N fbm of rough dimension, depending upon the green
moisture content and the moisture content to which it was dried.
Figure 3 gives a cumulative distribution of green weight per cubic foot
representing 556 individual pieces.
Sixty per cent of the pieces measured had
green weights between 35 and 45 pounds per cubic foot.
Specific gravit
and ring count
Specific gravity determinations were made on 20 specimens from each of 10
of the test charges,
An average specific gravity value of 0.424 was obtained
using the oven-dry weight and green volume.
Sixty per cent of the specific grav-
ity values fell between about 0.39 and 0.46 (Figure 4).
-14-
Figure
5
through 15 are end-grain photographs of the kiln samples used in
the kiln-dried charges.
The individual sections are marked with their specific
gravity values. An indication of the variation in ring count can be obtained by
an examination of these photographs.
count of 14 rings per inch (Figure 9).
Section number 5 from charge 5 had a ring
Section number 19 from charge 9 had a
ring count of 2 1/2 rings per inch (Figure 14).
These sections represented the
extreme ring-count values found in kiln samples from all charges.
Drying rate--kiln schedules
Figures 23 through 32 show kiln schedules and drying rates for 20 kiln
samples per charge.
Drying time to 18 per cent average moisture content for
charges 2, 4 and 5A was about 72-75 hours.
Drying time to 18 per cent average
moisture content for high temperature-high humidity schedules (charges 8 and 9)
was about 50 hours.
Drying time for a low temperature-high humidity schedule
(charge 10) was about 90 hours to an average moisture content at 18 per cent.
This charge had a low average green moisture content of about 34 per cent.
If
the green moisture content of charge 10 had been from 40 to 45 per cent, the
drying time to 18 per cent would have been much longer.
Green moisture content
Figure 33 shows the variation in green moisture content of lumber in the
10 charges which were kiln-dried.
The median green moisture content value was
40 per cent, with 60 per cent of the boards having green moisture contents between 35
and 52
per cent.
Uniformity of final moisture content
Figures 34 through 43 show moisture-meter readings in the kiln-dried
charges.
Charge 2 showed more uniformity in final moisture content than did
charge 3, probably because charge 2 was subjected. to
three-week winter storage
-15-
period in the cooling shed before uristickering.
In general, the schedules using
high final humidities showed mere uniformity in final moisture content than did
those with low final humidities.
Moisture-meter readings
Figure 44 gives a comparison of moisturemeter readings and oven-test
moisture-content values found in the kiln-dried lumber.
Close correlation was
obtained between oven-test values on kiln samples and moisture-meter readings
on an S4S boards within iridividu]. charges.
Shrinkage during kiln-drying
Cumulative distribution curves for rough-green and rough-dry thicknesses
of the lumber used in the study are shown in Figure 45.
The rough-dry measure-
ments were made on lumber which was dried to an average of about 12 per cent
moisture content.
An exaijnation of this curve will show an average shrinkage
in thickness of about 3.5 per cent in drying from green to 12 per cent average
moisture content.
Figure 46 gives a cumulative distribution of shrinkages in width from
green to two different moisture-content levels.
When drying to 1
per cent
average moisture content the median shrinkage value was about 2.2 per cent, with
80 per cent of the boards shrinking less than 2.8 per cent.
When drying to 12
per cent average moisture content the median shrinkage value was about 3.4 per
cent, with 80 per cent of the boards shrinking less than 4.1 per cent.
Residual shrink.
In order to determine the extent of additional shrinkage which dimension
lumber would undergo when drying from the kiln-dried moisture content to that
reached in use, sections were cut from 20 kiln samples in each charge and measured
in width beore and after being conditioned to equilibrium with 65 per cent rela-
-16-
tive humidity at 70 deg F (approximately 12 per cent equilibrium moisture content).
The average residual-shrinkage values obtained are shown in Figure 47.
When lum-
ber was kiln-dried to 18 per cent average moisture content the average additional
shrinkage was found to be about 1.0 per cent.
When kiln-dried to 15 per cent
average moisture content, the average additional shrinkage was found to be about
0.6 per cent.
Average residual shrinkage values for lumber dried to equilibrium with
25 per cent relative humidity at 100 deg F also are shown in Figure 47.
Figure 48 gives a cumulative distribution curve for residual shrinkage of
lumber which was kiln-dried to 16-18 per cent moisture content.
The
median
residual-shrinkage value on this curve is about 0.65 per cent, with 90 per cent
of the boards having less than 1.5 per cent residual shrinkage in width.
CONCLUSIONS
Young-growth Douglas-fir dimension lumber was dried to moisture contents
down to 12 per cent without excessive degrade when the lowest EMC level in the
schedule was kept at 8 per cent or higher.
The lower the ENC during the low
relative humidity step in the schedule, the higher the resulting degrade was
found
to be.
Of three variables which affected degrade in young-growth Douglas-fir
dimension--the EMC of the low-humidity step in the schedule, the initial drybulb temperature, and the final average moisture content--the most important was
the
4C of the low-humidity step.
Temperatures up to 200 deg F were used in drying this material without
excessive degrade when EMC was closely controlled at a sufficiently high level.
-17-
REMARKS
Because of the important effect on degrade of the low EMC step in the
schedule, it would be wise to keep the EMC during the kiln schedule as high as
possible consistent with a reasonable drying time, in the drying of young-growth
Douglas-fir dimension.
The dry-bulb temperature should also be kept as high as
possible during the schedule, within limits that permit accurate cortrol of the
desired EMC as well as reasonable steam consumption.
Certain kiln schedules which have been observed in use for kiln-drying
young-growth Douglas-fir dimension lumber could be modified to reduce degrade by:
Raising the EMC used during the low-humidity step of
the schedule,
Raising the initial dry-bulb temperature to overcome
the retarding effect which a higher EMC has on drying
time.
It must be recognized that in dry kilns which exhibit large longitudinal or cyclic
variations in dry-bulb temperature, the substitution of a high-temperature schedule for a satisfactory low- or medium-temperature schedule might lead to excessive-
ly high degr1e percentages because of loss of control over EMC,
Drying of young-growth Douglas-fir dimension to an average of 16-18 per
cent moisture content is believed to be satisfactory if the lumber is to be used
for general construction purposes, for the following reasons:
An average moisture content of 16-18 per cent can be
obtained in a short time using a kiln schedule which
results in low degrade.
Shipping weight is not decreased greatly by drying to
moisture content levels below 18 per cent.
Residual shrinkage of lumber which has been dried to an
average of 18 per cent moisture content is low enough to
be satisfactory for most construction uses.
-18-
BIBLIOGRAYHY
Herman, Albert and Gould, Clark W.
.
Common Douglas
Kiln-drying
Fir Boards and Dimension. Forest Products Laboratory, U. S. Forest
Service, 11adison, Wisconsin.
Johnson, Herman N. Degrade in Kiln Drying of Douglas-fir Common and Finish.
U. S. Forest Service, 1927.
Knauss, A. C. "Can Common Grades of Douglas-fir Lumber be Successfully
Kiln-dried?" Unpublished Report, West Coast Lumbermen's Association,
1927.
Anon. "Resulting Degrade from Kiln Drying and Machining Douglas-fir Common."
Oregon_American Lumber Corporation. 1939.
-19-
Table 1. Total Degrade in No. 1 and No. 2 Common
Young-growth Douglas-fir Dinension Lumber.
Charge
Final average
moisture content
Total degrade fbrn basis)
No. 1 Common
No. 2 Common
Per cent
Per cent
Per cent
2
18.4
10.7
4.8
3
18.0
9.7
5.5
4
14.9
13.5
11.3
5
7.8
21.2
5.1
SA
12.4
6.4
2.8
6
12.1
8.3
1.1
7
12.5
4.0
3.0
8
16.4
4.1
3.7
9
16.1
5.6
3.3
10
17.6
3.6
2.4
8.7
4.3
AU Charges
-20-
Table 2.
Charge
Kiln-dried 848 Recovery in Grade from No. 1 Common
Young-growth Douglas-fir Dimension Lumber.
Final average
moisture content
Recovery in'ade (fbm basis)
No. 30
No. 20
No. 40
No. 10
Loss
Per cent
---
2
18.4
89.3
1.8
8.8
3
18.0
90.3
7,4
2.2
4
14.9
86.5
7.8
5.7
-
5
7.8
78.8
14.3
4.9
--
5A
12.4
93.6
5.6
0.7
6
12.1
91.7
8.3
0.0
7
12.5
96.0
2.6
0.9
8
16.4
95.9
3.8
0.0
9
16.1
94.4
5.6
0.0
10
17.6
96.4
0.9
2.4
0.1
0.1
0.0
20
0.1
--
-
0.0
0.5
0.3
0.0
0.3
-21-
Table 3.
Kiln-dried 54S Recovery in Grade from No. 2 Common
Dimension Lumber.
Ioung-growth Douglas-fir
Charge
Final average
moisture contort
Recovery in grade (fbm basis)
No. 4C
No. 3C
Loss
No. 2C
Per
cent
2
18.4
95.2
4.8
0.0
0.0
3
18.0
94.5
4.6
0.8
0.1
4
14.9
88.7
11.3
0.0
0.0
5
7.8
94.9
1.6
0,0
3.5
5A
12.4
97.2
2.7
0.0
0.1
6
12.1
98.9
0.5
0.5
0.1
7
12.5
97.0
3.0
0.0
0.0
a
16.4
96.3
3.2
0.0
0.5
9
16 1
96.7
3.1
0.0
0.2
10
17.6
97,6
2.1
0.0
0.3
-22-
Table 4.
Charge
low relative
humidity
step
Effects of Low W Step in Schedule on Degrade Percentages.
Faildown
below No. 2C
Total degrade
No .1C
No.2C
Avg
No,1C
No.2C
Avg
No .1C
Degrade from other
than knot damage*
No.2C
vg
No.1C
No.20
Avg
Per cent
Per cent
7.8
8.9
4.8
6.8
3.8
1.8
2.8
6.9
3.0
4.9
11.3 12.4
57
11.3
8.5
6.2
4.0
5.1
7.3
7.3
73
5.1
13.1
6.9
5.1
6.0
6.2
0.0
3.1
15.0
5.1
10.0
6.4
2.8
4.6
Q
2,8
12.9
6.0
9.5
56
6.0
5.8
5.1
1.4
3.3
7.8
4.5
6.2
2
4.4
10.7
4
4.3
13.5
5
3.3.
21.2
5k
4.3
Average
above
group
Degrade from
knot damage
4.8
2.2
Q,Q
2.5
3
7.8
9.7
5.5
7.6
2.3
5.5
3.9
6.0
1.6
3.8
3.7
3.9
3..8
6
9.0
8.3
1.1
4.7
0.0
1.1
0.5
7.4
0.0
3.?
0.9
1.1
1.0
7
8.8
4.0
3.0
3.5
1.4
3.0
2.2
2.6
0.6
1.6
1.4
24
1.9
8
7.7
4.1
3.7
3.9
0.3
3.7
2.0
2.3
0.0
1.1
LB
3.?
2.7
9
7.,?
5.6
3.3
4.4
0.0
3.3
1.7
4.9
3,1
4.0
0.?
0.2
0.4
10
11 0
3.6
2.4
3.0
2.7
2,4
2.5
0.9
1.6
1.2
2.7
0.8
1.7
5.9
3.2
4.5
1,1
3.2
2.1
4.0
1.1
2.6
1.8
2.0
1.9
Average
above
group
* Includes degrade from planer split, warp, season checks,
shake
and grain separation.
-23'-
Table 5.
Effects of Low HIC Step in Schedule on Various
Causes of Degrade.
Degrade from various causes*
EaVIC of
low relative
hunu.dity
Charge
step
Planer split
and warp
Loose knots
and ege nots
No.IC
No.2C
Avg
No.10
No.20
Season checks
Avg
No.10
Knotholes
No.20
Avg
No.10
No.20
Avg
Per cent
Per cent
2
4.4
1.0
0.9
0.9
2.0
1.8
1.9
4.8
0.9
2.9
2.8
0.9
l.
4
4.3
3.0
0.8
1.9
4.1
5.2
4.6
0.?
0.0
0.3
3.2
3.2
3.2
5
3.3
2.4
0.0
1.2
14.6
5.1
9.8
0.0
0.0
0.0
3.8
0.0
1.9
5A
4.3
1.4
0.0
0.7
2.2
2.7
2.5
0.0
0.0
0.0
2,8
0 0
1.4
1.9
0.4
1.2
5.7
3.8
4.7
1.4
0.2
0.8
3.2
1.0
2.1
Average
above
group
3
7.8
3.7
0.8
2.2
0.7
0.1
0.4
0.0
0.0
0.0
2.3
0.8
1.5
6
9.0
1.8
0.0
0.9
0.9
0.6
0.7
0.0
0.0
0.0
5.6
0.0
2.8
7
E.8
0.9
0.6
0.7
1.4
1.2
1.3
0.0
0.6
0.3
1.7
0.0
0.8
8
7.?
0.8
0.0
0.4
1.8
3.6
2.7
0.0
0.0
0.0
1.5
0.0
0.7
9
7.7
3.3
1.2
2.2
0.0
0.2
0.,1
0.0
0.0
0.0
1.6
1.9
1.7
10.
11.0
0.9
1.6
1.2
2.7
0.8
1.7
0.0
0.0
0.0
0.0
0.0
0.0
1.9
0.7
1.3
1.2
1.1
1.1
0.0
0.1
0.05
2.1
0.45
1.2
Average
above
group
*Degrade from shake and grain separation is riot inc1ued.
-24Table 6.
Charge
Average
moisture
content
Effects of Final Average Kiln-dried Moisture Content
on Degrade Percentages.
Total degrade
Avg
No.20
No.1C
Falidown
below No 2C
No.20
Avg
No.1C
Degrade from
knot damage
No.1C
No.20
Avg
Degrade from other
than knot damage*
No.2C
No.10
AvI
Per cent
Per cent
2
18.4
10.7
4.8
7.8
8.9
4.8
6.8
3,8
1.8
2.8
6.9
3.0
4.9
3
18.0
9.7
5.5
7.6
2.3
5.5
3,9
6.0
1.6
3.8
3.7
3.9
3.8
10
17.6
3.6
2.4
3.0
2.7
2.4
2.5
0.9
1.6
1.2
2.7
0.8
1.7
8
16.4
4.1
3.7
3.9
0.3
3.7
2.0
2.3
0.0
1.1
1.8
3.7
2.7
9
16.1
5.6
3.3
4.4
0.0
3.3
1.7
4.9
3.1
4.0
0.7
0.2
0.4
4
14.9
13.5
11.3
12.4
5.7
11.3
8.5
6.2
4.0
5.).
7,3
7.3
7.3
7.9
5.2
6.5
3.3
5.2
4.2
4.0
2.0
3.0
3.8
3.1
3.5
Average
above
group
7
12.
4.0
3.0
3.5
1.4
3.0
2.2
2.6
0.6
1.6
1.4
2.4
1.9
5A
12.4
6.4
2.8
4.6
0.8
2.8
1.8
4.2
0.0
2.1
2.2
2.8
2.5
6
12.1
83
1.1
4.7
0.0
1.1
0.5
7.4
0.0
2.7
0.9
1.3.
1.0
5
7.8
21.2
5.1
13.1
6.9
5.1
6.0
6.2
0.0
3.1
15.0
5.1
10.0
10.0
3.0
.6.5
23
3.0
2.6
5.1
0,1
2.4
4.9
2.8
3.8
Average
above
group
* Includes degra2e from planer split, warp, season checks, shake and grain separation.
-25-
Tb10 7.
Charge
Average
moisture
content
Effects of Final Average Kiln-dried Moisture Content on
Various Causes of Degrade.
Loose knots
and edge knots
No.20
No.10
Avg
Degrade from various causes
Planer split
and warp
Season checks
No.10
No.2C
Avg
No.1C
No.20
Avg
Per cent
No.10
Knotholes
No.2C
Avg
Per cent
2
18.4
1.0
0.9
0.9
2.0
1.8
1.9
4.9
0.9
2.9
2.8
0.9
1.8
3
18.0
3.7
0.8
2.2
0.7
0.1
0.4
0.0
0.0
0.0
2.3
0.8
1.5
10
7.6
0.9
1.6
1.2
2.7
0.8
1.7
0.0
0.0
0.0
0.0
0.0
0.0
8
16.4
0.8
0.0
0.4
1.8
3.6
2.7
0.0
0.0
0.0
1.5
0.0
0.7
9
16.1
3.3
1,2
2.2
0.0
0.2
0.1
0.0
0.0
0.0
1.6
1.9
1.7
4
14,9
3.0
0.8
1.9
4.1
5.2
4.6
0.7
0.0
0.3
3.2
3.2
3.2
2.1
0.9
1.5
1.9
1.9
1.9
0.9
0.1
0.5
1.9
1.1
1.5
Average
above
group
7
12.5
0.9
0.6
0.7
1.4
1.2
1.3
0.0
0.6
0.3
1.7
0.0
0.8
5A
12.4
1.4
0.0
0.7
2.2
2.7
2.5
0.0
0.0
0.0
2.8
0.0
1.4
6
12.1
1.8
0.0
0.9
0.9
0.6
0.7
0.0
0.0
0.0
5.6
0.0
2.8
5
7.8
2.4
0.0
1.2
14.6
5.1
9.8
0.0
0.0
0.0
3.8
0.0
1.9
1.6
0.1
0.9
4.8
2.4
3.5
0.0
0.15
0,].
3,5
0.0
1.7
Average
above
group
* D'grade from shake and grain separation is not included.
-26Table 8.
Charge
Initial
dry bulb
temp
Effect of Initial Dry-bulb Temperature on Degrade Percentages.
Total degrade
No.2C
Avg
No.10
Faildown
below No. 2C
No.10
No.20
Avg
Degrade from
knot damage
No.1C
No.20 Avg
Degrade from other
than knot damage*
No.10
No.20
Avg
Percent
gF
5
160
21.2
5.1
13.1
6.9
5.1
6.0
6.2
0.0
3.1
15.0
5.1
10.0
6
180
8.3
1.1
4.7
0.0
1.1
0.5
7.4
0.0
3.7
0.9
1.1
1.0
7
180
4.0
3.0
35
1.4
3.0
2.2
2.6
0.6
1.6
1.4
2.4
1.9
8
200
4.1
3.7
3.9
0.3
3.7
2.0
2.3
0.0
1.1
1.8
3.7
2.7
9
200
5.6
3.3
44
0.0
3.3
1.7
4.9
3.1
4.0
0.7
0.2
0.4
8.6
3.2
5.9
1.7
3.2
2.5
4,7
0.7
2.7
4.0
2.5
3.3
Average
above
group
2
135
10.7
4.8
7.8
8.9
4.8
6.8
3.8
1.8
2.8
6.9
3.0
4.9
3
135
9.7
5.5
7.6
2.3
5.5
3.9
6.0
1.6
3.8
3.7
3.9
3.8
4
135
13.5
11.3
12.4
5.7
11.3
8.5
6.2
4.0
5.1
7.3
7.3
7.3
5A
135
6.4
2.8
4.6
0.8
2.8
1.8
4.2
0.0
2.1
2.2
2.8
2.5
130
3.6
2.4
3.0
2.7
2.4
2.5
0.9
1.6
1.2
2.7
0.8
1.7
8.8
5.3
7.0
4.1
5.4
4,7
4.2
1.8
3.0
4.6
3.6
4.1
10
Average
above
group
* Includes degrade from planer split, warp, season checks, shake and grain separation.
-2?-
Table 9.
Effect of Initial Dry-bulb Temperature on Various Causes of Degrade.
Degrade from various causes*
Charge
Initial
dry-bulb
temp
Loose knots
and edge knots
Avg
No.2C
No.1C
Planer split
and warp
Avg
No.2C
No.1C
Season checks
No.1C
No.2C
Avg
No.10
Knotholes
No.20
Avg
L cent
5
160
2.4
0.0
1.2
14.6
5.1
9.8
0.0
0.0
0.0
3.8
0.0
1.9
6
180
1.8
0.0
0.9
0.9
0.6
0.7
0.0
0.0
0.0
5.6
0.0
2.8
7
180
0.9
0.6
0.7
1.4
1.2
1.3
0.0
0.6
0.3
1.7
0.0
0.8
8
200
0.8
0.0
0.4
1.8
3.6
2.7
0.0
0.0
0.0
1.5
0.0
0.7
9
Average
200
3.3
1.2
2.2
0.0
0.2
0.1
0.0
0.0
0.0
1.6
1.9
1.7
1.8
0.4
1.1
3.7
2.2
2.9
0.0
0.1
0.06
2.8
0.4
1.6
above
group
2
135
1.0
0.9
0.9
2.0
1.8
1.9
4.9
0.9
2.9
2.8
0.9
1.8
3
135
3.7
0.8
2.2
0.7
0.1
0.4
0.0
0.0
0.0
2.3
0.8
1.5
4
135
3.0
0.8
1.9
4.1
5,2
4.6
0.7
0.0
0.3
3.2
3.2
3.2
5A
135
1.4
0.0
0.7
2.2
2.7
2.5
0.0
0.0
0.0
2.8
0.0
1.4
130
0.9
1.6
1.2
2.7
0.8
1.7
0.0
0.0
0.0
0.0
0.0
0.0
2.0
0.8
1.4
2.3
2.1
2.2
1.1
0.2
0.6
2.2
1.0
1.6
10
Average
above
group
* Degrade from shake and grain separation is not included.
-28Table 10. Effect of Low aVIC Step in Schedule on Dollar Recovery
per Thousand Board Feet of Kiln-dried Dimension Lumber.
EMC of
low relative
humidity
step
L
Grade of
kiln-dried,
planed
lumber
Value per N fbm of rough-green lumber
after kiln-drying and nrnehining
Select Str
No.1 Common
No.2 Common
cent
Se]. Str
$69.74
No, 10
12.79
$71.34
No. 2C
5.32
5.62
$71.44
No. 30
0.27
2 70
2.75
No.40
0.12
3.3-4.4
All grades $88.24
Se]. Str
7.7-11.0
$74.19
78.75
No. 1C
7.87
77.16
No. 20
3.19
3.65
73.57
0.49
1.51
No. 30
No, 40
0605
All grades $89.8].
$81.30
$75.13
SUNNARY
Total value per N fbzu (848)
Grade
Low ENC
schedule
High ENC
schedule
Se? Str
$88.24
$89.8].
$92.00
$78 .50
No. 1C
79.66
81.30
82.00
68.50
No. 2C
74.19
75.13
76.00
65.25
No. 30
54600
48.00
No. 40
23.00
18.50
KD value with
no degrade*
Green value with
no degrade*
* Prices based on Crows Price Reporter, August 20, 1953, average of "Most
Sales". A price diferential of $10 was assumed between Number 1 Commo and
Select Structural,
-29-
Table 11.
Percentages of Green Pieces Containing Black
Knots of Over 3/4-inch Diameter.
Lumber grade
Charge
Sal Str and No. 1C
No. 2C
Per cent
Per cent
3
16.9
20.7
4
13.5
U.8
5A
15.4
12.1
6
24.2
17.3
7
22.3
22.0
8
11.6
10.1
9
22,6
26.1
10
Above
charges
28.2
18.1
18.5
FIGURE I.
RELATIONSHIP OF SHIPPING WEIGHT TO AVERAGE
MOISTURE CONTENT IN 2- by 8- INCH YOUNG-GROWTH
DOUGLAS-FIR , SURFACED FOUR SIDES (AVERAGE OF
NO I AND 2 COMMON).
FIGURE 2. WEIGHT PER M FBM BY MOISTURE CONTENT;
ROUGH 2-by 8- INCH by 16-FOOT YOUNG-GROWTh
DOUGLAS-FIR (AVERAGE OF NO. I AND NO. 2
COMMON).
2800
0
38
700
0
0
0
U)
Li
36
2600
LU
aU)
U)
U-
0)
2 500
. .0
34 0
0
z
S
32
24 00
I
0
0
LU
- 30 0
I0
2 300
I.-
(D
z
LU
aa-
U)
0
0
I.-
I
S
LU
0
a-
0
0
0
28
0
2200
0
00
0
21 00
0
2
.
10
S.
S.
S
S
0
24
2000
0
S
0
30
20
MOISTURE CONTENT ,
40
50
PER CENT
60
65
0
10
30
20
MOISTURE CONTENT,
40
50
PER CENT
6
FIGURE
3.
CUMULATIVE DISTRIBUTION OF DENSITY VALUES
IN 2-by8-INCH GREEN DOUGLAS-FIR.
S
S
S
S
S
S
0
S
C)
NOTE
556 INDIVIDUAL MEASUREMENTS
REPRESENTED
S
S
I
S_S.
)
0
25
30
FIGURE 4.
I
35
40
45
50
GREEN WEIGHT, LB PER CU FT
55
60
CUMULATIVE DISTRIBUTION OF SPECIFIC GRAVITY
VALUES IN 2- B'( 8-INCH BY 16-FOOT YOUNGCHARGES
GROWTH DOUGLAS-FIR:
5A, 6,
I-
7,
I,
3, 4, 5,
8, 9 AND 10.
100
z
Ui
U
Ui
a>-
AVERAGE SPECIFIC GRAVITY
I>
OF 197 PIECES, BASED
ON GREEN VOLUME AND
OVEN-DRY WEIGHT, WAS
0
0
0. 424
LI-
U
Ui
54O
9
Ui
Ui
-J
0
0
0.35
040
045
SPECIFIC
050
GRAVITY
0.55
0.60
0.65
&
.p.-
r-
0*.
END GRAIN AND SPECIFIC GRAVITY
OF KILN SAMPLES,FROM CHARGE I.
3fl9IJ
END GRAIN OF KILN SAMPLES
FROM CHARGE
2.
II
F
OP
6
AND
OF KILN SAMPLES
3II33dS
END GRAIN
-O
3.
!WA
FIGURE
p
-
6f
al
END GRAIN AND SPECIFIC GRAVITY
OF KILN SAMPLES FROM CHARGE 3.
zt. ()
-
FIGURE 5.
GRAVITY
CHARGE 4.
GI4AROE 5 PlO.IE1
2 h4
K074%AvMC AvSpG. 0.4
A PflQ,JECT
I2M
- 53
.. IL
Z'I.3I
1.41
eIIT
5. 4
HIW/
'.7
Ii))))))iIJ
'
:
4.
8. 80
FIGURE 9.
END GRAIN AND SPECIFIC GRAVITY
FIGURE
4
9
END GRAIN
10.
AND SPECIFIC
GRAVITY
OF KILN SAMPLES FROM CHARGE 5A.
OF KILN SAMPLES FROM CHARGE 5.
CHAROt 6 P'OIET 5h(.')
RD e%AMc ASpG. C4I
Sl
FIGURE
II.
r
035-52
END GRAIN AND SPECIFIC GRAVITY
OF KILN SAMPLES FROM CHARGE 6.
FIGURE
2
END
GRAIN
AND
SPECIFIC
GRAVITY
OF KILN SAMPLES FROM CHARGE 7.
VVL
'9'JEUI 32l6)
31;% 4,M1; 1;pO. 44
4
4
Ai
38
r'
3
,;
3'
Tiri
%
L.
39
2
38
'4
FIGURE
END GRAIN AND SPECIFIC GRAVITY
OF KILN
SAMPLES
FROM CHARGE
13.
FIGURE
5
FIGURE
14.
8.
END GRAIN AND SPECIFIC GRAVITY
OF KILN SAMPLES FROM CHARGE
FIGURE
END GRAIN AND SPECIFIC GRAVITY
OF KILN SAMPLES FROM CHARGE 9.
16.
CONDITION
SURFACING:
OF KNOTS AFTER
CHARGE
3.
FIGURE
17.
FIGURE
CONDITION OF KNOTS AFTER
SURFACING:
CHARGE 4.
lB.
CONDITION OF KNOTS
SURFACING:
AFTER
CHARGE 5A.
S
FIGURE
II.
CONDITION OF KNOTS
SURFACING:
CHARGE
AFTER
6.
FIGURE 20.
CONDITION
OF
KNOTS AFTER
SURFACING;
CHARGE 7.
FIGURE 23. YOUNG-GROWTH 2-by 8- INCH DOUGLAS-FIR.
. ..-. . -
Iu,J
FIGURE 24. YOUNG-GROWTH 2-by 8-INCH DOUGLAS-FIR,
2,
CHARGE
.
3,
CHARGE
DRYING RATE & KILN SCHEDULE.
.
DRY BULB
U-
160
DRY
40
WET BULS_\
ioo
SAMPLE
hlH
BULBThH\
1\
F-
I
0
80
I-
2
UJ
60
w
40
___
SAMPLES
Iz 40
z0
C.)
III
20
LOW SAMPLE
0
0,
0
20
o
60
80
TIME, HOURS
IHSAMPJ
0
, AVERAGE OF TWENTY
100
120
20
'
LOW SAMPLE
AVERAGE OF
TWENTY SAMPLES
10
0
20
40
60
80
TIME , HOURS
120
140
FIGURE 25. YOUNG-GROWTH
2-by 8INCH DOUGLAS- FIR;
CHARGE
4,
DRYING RATE & KILN SCHEDULE.
180
FIGURE 26. YOUNG-GROWTH 2-by 8- INCH DOUGLAS-FIR
CHARGE 5,
DRYING RATE & KILN SCHEDULE.
DRY BULB
I
Ll
0
WET BULB
140
Cl)
z
20
.r-J
Lu
I
.
80
HIGH SAMPLE
I-
z
w
0 60
cr
60
AVERAGE OF
TWENTY
Lii
SAMPLES1
24O
zLii
z0
Lii
4
20
Ii
0
4
I-
4
Iii
Z
WET BULB
HIGH SAM PLE
AVERAGE
OF TWENTY
SAMPLES
LOW SAMPLE
LOW SA
C,,
0
0
L'
U-
2
I-
0
LI
DRY BULB
20
40
TIME ,
60
HOURS
80
0
100
120
40
80
TIME ,
120
160
200
220
1
FIGURE 27 YOUNG-GROWTH 2-by8-INCH DOUGLAS-FIR;
CHARGE 5A,
DRYING RATE 8 KILN SCHEDULE
FIGURE 28.
DRY
YOUNG-GROWTH 2- BY 8-INCH DOUGLAS-FIR;
CHARGE 6,
DRYING RATE & KILN SCHEDULE.
BULB
180
0
U
C
rwET BULB
zU
U
Ii
I-
cr
I-
IWET
BULB
BULB
160
0
U
140
I-
80
6
AVERAGE OF
TWENTY SAMPLES r
0.
\DRY
Lii
6O
Iii
I
HIGH SAMPLE
z 40
4
Ui
I.-
z
HIGH SAM PLE
0
0
AVERAGE OF TWENTY
20
20
-
0
LOW SAMPLE
0
0
20
40
60
TIME, HOURS
80
tOO
120
140
20
40
60
TIME, HOURS
80
100
120
FIGURE 30.
FIGURE 29. YOUNG-GROWTH 2-by 8-INCH DOUGLAS-FIR
CHARGE 7,
DRYING RATE & KILN SCHEDULE.
U-
YOUNG-GROWTH 2- BY 8-INCH DOUGLAS-FIR;
CHARGE 8,
DRYING RATE & KILN SCHEDULE.
20
180
BULB
U-
jWET BULB
Ui
DRY
ITO
LDRY BULB
,-WET
160
-
BULB
Lz
UU-
0
120
UU-
0
U)
2
,_
2
LQ
C-)
80
I-
zUi
I-
0
HIGH SAMPLE
Ui
-
0
10
100
60
--
80
I-
z
Ui
C.)
a.
TWENTY SAMPLES
40
20
0
20
60
U
AVERAGE OF
C-)
.
I-
zU
z0
0
w 20
:
LOW
40
60
80
TIME , HOURS
00
120
SAMPLE
'.:HIGH
AVERAGE 0
LOW
TWENTY SAMPLES
SAMPLE
0
0
20
40
60
TIME, HOURS
80
100
120
FIGURE 31, YOUNG-GROWTH 2-by 8-INCH DOUGLAS-FIR,
9,
CHARGE
DRYING RATE 8 KILN SCHEDULE
U. 200
FIGURE 32. YOUNG-GROWTH 2- BY 8-INCH DOUGLAS-FIR;
CHARGE 10,
DRYING RATE & KILN SCHEDULE.
DRY BULB
LU
f-WET BULB
U.
140
LU
0
1-DRY BULB
Lu
120
NOTE: 2 HOURS STEAM
AND WATER SPRAY
a-
BEFORE OPENING KILN
too
k-WET BULB
Lu
L&1
'-
100
I-
z
U-
z
0
80
Ci)
z
Lu
HIGH SAMPLE
Lu
a.
Lu
0.
i-
60
zLu
Iz0
I-.
z
Lu
0
0
80
LU
C,
40
60
HIGH SAMPLE
40
AVERAG
-
.
20
S
LOW
0
20
-
20
0
0
S
S
S
SAMPLE
40
60
TIME
, HOURS
80
100
120
20
40
60
TIME , HOURS
80
tOO
120
FIGURE 33.
CUMULATIVE PERCENTAGES OF PIECES ACCORDING
TO MOISTURE CONTENT IN GREEN 2- BY 8-INCH
YOUNG-GROWTH DOUGLAS-FIR;
I-
TEN CHARGES.
I0O
U
0
LU
a-
8O
LU
NOTE
z0
201 INDIVIDUAL OBSERVATIONS REPRESENTED
0
i6O
D
I(1)
0
z
40
LU
ILl
20
ILl
U)
LU
0
LU
a-0
40
FIGJJRE
60
80
100
120
140
GREEN MOISTURE CONTENT , PER CENT
34.
DISTRIBUTION OF MOISTURE METER READINGS
IN 2-by8-INCH YOUNG -GROWTH DOUGLAS-FIR,
CHARGE 2, KILN-DRIED TO 18.4 % AVG M.C.
I-
0
bc
.
w
0
a-
(8C
2
0
4
LU
S
6C
I-
(Li
2
LU
.
4C
NOTE
MOISTURE METER READINGS
ON 51 WEIGH PIECES ONLY
-J 2C
LU
U)
LU
0
0
LU0
0
14
24
22
18
20
PER CENT
MOISTURE METER READINGS
16
160
FIGURE 35.
DISTRIBUTION OF MOISTURE METER READINGS
IN 2-by8-INCH YOUNG-GROWTh DOUGLAS-FIR,
CHARGE 3, KILN-DRIED TO 18.0 04 AVG MC.
I-
z 100
uJ
U
a:
.
LU
a-
z
80
0
.
LU
a:
A
6O
ILU
LU
4O
S
.
20
LU
U)
LU
U
LU
0
8
10
14
12
IR
I
MOISTURE METER READ NGS,
99
21)
2
PER CENT
FIGURE 36. DISTRIBUTION OF MOISTURE METER READINGS IN 2- BY 8INCH YOUNG-GROWTR DOUGLAS-FIR;
CHARGE 4, KILN-DRIED TO 15.2 %AVG M C.
I-
z
Iii 10
C-)
a:
LU
a-
0
8O
322 PIECES IN CHARGE
LU
a:
a:
.
W
I- 60
LU
Ui
S
a:
40
C,)
0
S
0
-J
LLI
S
Cl)
LU
0
LU
a-
IA
I-,
IJ
MOISTURE
le
METER READINGS,
)0
10
IQ
PER CENT
0
c4
FIGURE 37. DISTRIBUTION OF MOISTURE METER READINGS
IN 2-by8- INCH YOUNG -GROWTH DOUGLAS-FIR;
CHARGE 5, KILN-DRIED TO 7.8 % AVG N C.
I-
z
100
Ui
a-
0
z 80
0
Lii
2O
Ui
U)
U
0
U
0
'
8
10
12
4
16
MOISTURE METER READINGS, PER CENT
18
20
FIGURE 38. DISTRIBUTION OF MOISTURE METER READINGS IN 2- BY
8-INCH YOUNG-GROWTH DOUGLAS-FIR; CHARGE 5-A,
KILN-DRIED TO 12.4 % AVG MC.
WI 'Ju
0
W
a-
z
0
W
W
I-
W
W
I- 40
(1)
0
NOTE
309 PIECES IN CHARGE
Ui
2:
U)
Ui
0
Ui
0
6
8
10
12
14
16
MOISTURE METER READINGS, PER CENT
18
FIGURE 39.
DISTRIBUTION OF MOISTURE METER READINGS IN 2- BY 8-INCH YOUNG-GROWTH
DOUGLAS-FIR; CHARGE 6, KILN-DRIED TO
12.1 % AVG MC.
I2 IOO
LU
0
.
ii:
LU
0
z
80
I
LU
0
60
2
307
LU
NOTE
PIECES IN CHARGE
40
0
520
LU
U)
LU
0
LU
ö0Q
.
4
S
8
10
IS
14
12
U
MOISTURE METER READINGS, PER CENT
FIGURE 40.
DISTRIBUTION OF MOISTURE METER READINGS IN
2- BY 8-INCH YOUNG-GROWTH DOUGLAS-FIR;
CHARGE 7, KILN-DRIED TO 12.5 % AVG MC.
I.-
2I
Lii
0
S
Lii
S
a-
2
90
Iii
.
Lii
60
I.-
LU
S
2
w
I- 40
U)
NOTE
0
2
307
PIECES IN CHARGE
S 20
LU
U)
LU
0
LU
a-
0j
0
0
S
8
10
12
14
16
MOISTURE METER READINGS, PER CENT
18
2
FIGURE 41. DISTRIBUTION OF MOISTURE METER READINGS
IN 2-by8- INCH YOUNG-GROWTH DOUGLAS-FIR,
CHARGE 8, KILN- DRIED TO 16.4 % AVG M C.
I-
2
w
U
w
0
(.
2
0
80
w
Lu
I-
NOTE
Lu
3I3 PIEC ES IN CH ARGE
U
IU,
0
10
12
14
20
18
16
22
24
MOISTURE METER READINGS, PER CENT
FIGURE 42.
CHARGE 9, KILN-DRIED TO 16.1 % AVG MC.
I.-
2
Ui
o
DISTRIBUTION OF MOISTURE METER READINGS
IN 2-by 8- INCH YOUNG -GROWTH DOUGLAS-FIR,
.
.1
.
'.,-
Lu
0
2
0
)
Ui
Lu
)
Lu
Lii
N OTE
316 PIECES IN CHARGE,
0
0
0
-J
Lu
0¼
U)
Lu
0
Lii
0
0
'4
tA
MOISTURE METER READINGS,
2ô
PER CENT
2
2
FIGURE 43. DISTRIBUTION OF MOISTURE METER READINGS IN 2- BY 8INCH YOUNG-GROWTH DOUGLAS-FIR;
CHARGE 10,
KILN-DRIED TO 17.6 S AVG MC
F-
zIO
LU
0
0
a:
LU
0
0'
z
Iii
a:
a:
LU
I-
LU
0
LU
a:
4
U)
o.
0
LU
NOTE
314 PIECES IN CHARGE
2'
0
Ln
U)
LU
C.,
LU
.
a-
10
14
12
MOISTURE
FIGURE 44.
20
18
16
METER READINGS,
22
24
PER CENT
MOISTURE METER READINGS COMPARED TO
OVEN-TEST MOISTURE CONTENT VALUES IN
2-by 8- INCH YOUNG-GROWTH DOUGLAS-FIR,
IN PER CENT.
I.-
Z20
LU
C)
a:
LU
0'
aC,
'I
0
z
LU
a:
a:
12
LU
F-
NOTE
LU
Lii
a:
OVEN-TEST SECTIONS CUT FROM
ROUGH KILN SAMPLES; MOISTURE
8
METER READINGS TAKEN AT
IU.,
3/8-INCH DEPTH ON ALL PIECES
0
LU
C.,
IN CHARGE AFTER SURFACING.
4
a:
LU
0
4
16
8
12
20
AVERAGE MOISTURE CONTENT, PER CENT (OVEN TEST)
FIGURE 45. CUMULATIVE DISTRIBUTION, IN PER CENT, OF THICKNESS IN 2BY 8-INCH YOUNG-GROWTH DOUGLAS-FIR; GREEN AND KILNDRIED.
r
I-
z
LU
C.)
A
Ui
0
LU
-J
60
U)
U)
z
REPRESENTED
(ROUGH,GREEN)
-r___
A
40
20
U)
Ui
0
Ui
a-
577 INDIVIDUAL MEASUREMENTS
!
LU
0
17
18
184 INDIVIDUAL MEASUREMENTS
REPRESENTED (ROUGH DRY)
AVERAGE MOISTURE CbNTENT
12 PER CENT
19
THICKNESS,
20
22
21
23
INCHES
FIGURE 46. CUMULATIVE DISTRIBUTION OF SHRINKAGE VALUES
DURING KILN-DRYING OF GREEN 2-by 8-INCH
YOUNG-GROWTH DOUGLAS-FIR.
100
LU
0
LU
°8o
DRIED TO IS PER
CENT AVERAGE
LU
-J
MC
.
.
60
4
DR
z
Cl)
ED TO 12
CENT AVERAGE
PER
MC.
40
20
0
.4
.i
1U
6
4
5
3
2
SHRINKAGE DURING KILN-DRYING, PER CENT (GREEN WIDTH BASIS)
2.4
FIGURE 47.
I-
RESIDUAL SHRINKAGE OF 2- BY 8-INCH YOUNGGROWTH DOUGLAS-FIR FROM KILN-DRIED
WIDTH TO EQUILIBRIUM WITH 25 AND 65
PER CENT RELATIVE HUMIDITY.
3.0
zUi
0
Ui.
aLii
0
4
z
1.0
I
U)
0
10
12
14
16
18
20
AVERAGE KILN-DRIED MOISTURE CONTENT, PER CENT
FIGURE 48. CUMULATIVE DISTRIBUTION OF RESIDUAL SHRINKAGE VALUES
IN 2-by 8-INCH KILN-DRIED,YOUNG-GROWTH DOUGLAS-FIR
WHEN DRIED FROM AVERAGE MOISTURE CONTENT OF 16- 18
PER CENT TO EQUILIBRIUM WITH 65 PER CENT RELATIVE
HUMIDITY.
I-
zuJ
0
0
U
LII
o
NOTE
w
99 INDIVIDUAL MEASUREMENTS REPRESENTED
46
.
uJ
0
4
.
z
0
U)
''
.
S
2
0
.
U)
w
0
Ui
a-
0
0
2
RESIDUAL SHRINKAGE,
3
4
5
6
PER CENT (KILN-DRIED WIDTH BASIS)
7
E
FIGURE 49.
FIGURE
51.
END GRAIN VIEW OF S4S
CHARGES 4 AND 5A.
DIMENSION:
OF S4S
DIMENSIONt
END GRAIN VIEW
CHARGE
8.
FIGURE 50
END GRAIN VIEW OF
CHARGES
FIGURE
52.
6 AND 7.
S4S
0 MENSION
END GRAIN VIEW OF S4S DIMENSION:
CHARGE
9.