J. B. (Joseph Bernard) Wagner.

Seasoning of Wood online

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The seasoning and kiln-drying of wood is such an important process in
the manufacture of woods that a need for fuller information regarding
it, based upon scientific study of the behavior of various species at
different mechanical temperatures, and under different drying
processes is keenly felt. Everyone connected with the woodworking
industry, or its use in manufactured products, is well aware of the
difficulties encountered in properly seasoning or removing the
moisture content without injury to the timber, and of its
susceptibility to atmospheric conditions after it has been thoroughly
seasoned. There is perhaps no material or substance that gives up its
moisture with more resistance than wood does. It vigorously defies the
efforts of human ingenuity to take away from it, without injury or
destruction, that with which nature has so generously supplied it.

In the past but little has been known of this matter further than the
fact that wood contained moisture which had to be removed before the
wood could be made use of for commercial purposes. Within recent
years, however, considerable interest has been awakened among
wood-users in the operation of kiln-drying. The losses occasioned in
air-drying and improper kiln-drying, and the necessity for getting the
material dry as quickly as possible after it has come from the saw, in
order to prepare it for manufacturing purposes, are bringing about a
realization of the importance of a technical knowledge of the subject.

Since this particular subject has never before been represented by any
technical work, and appears to have been neglected, it is hoped that
the trade will appreciate the endeavor in bringing this book before
them, as well as the difficulties encountered in compiling it, as it
is the first of its kind in existence. The author trusts that his
efforts will present some information that may be applied with
advantage, or serve at least as a matter of consideration or

In every case the aim has been to give the facts, and wherever a
machine or appliance has been illustrated or commented upon, or the
name of the maker has been mentioned, it has not been with the
intention either of recommending or disparaging his or their work, but
has been made use of merely to illustrate the text.

The preparation of the following pages has been a work of pleasure to
the author. If they prove beneficial and of service to his
fellow-workmen he will have been amply repaid.


September, 1917




Characteristics and Properties of Same - Structure
of Wood - Properties of Wood - Classes of Trees 1-7



Wood of Coniferous Trees - Bark and Pith - Sapwood and Heartwood - The
Annual or Yearly Ring - Spring- and Summer-Wood - Anatomical
Structure - List of Important Coniferous Trees 8-30



Wood of Broad-leaved Trees - Minute Structure - List of Most
Important Broad-leaved Trees - Red Gum - Range of Red Gum - Form
of Red Gum - Tolerance of Red Gum - Its Demands upon Soil and
Moisture - Reproduction of Red Gum - Second-growth Red Gum - Tupelo
Gum - Uses of Tupelo Gum - Range of Tupelo Gum 31-85



Different Grains of Wood - Color and Odor of Wood - Weight of
Wood - Weight of Kiln-dried Wood of Different Species - Figure in
Wood 86-97



General Remarks - Ambrosia or Timber Beetles - Round-headed
Borers - Flat-headed Borers - Timber Worms - Powder Post
Borers - Conditions Favorable for Insect Injury - Crude
Products - Round Timber with Bark on - How to Prevent
Injury - Saplings - Stave, Heading, and Shingle Bolts - Unseasoned
Products in the Rough - Seasoned Products in the Rough - Dry
Cooperage Stock and Wooden Truss Hoops - Staves and Heads
of Barrels Containing Alcoholic Liquids 98-113



Distribution of Water in Wood - Seasonal Distribution of Water in
Wood - Composition of Sap - Effects of Moisture on Wood - The
Fibre-Saturation Point in Wood 114-118



What Seasoning Is - Difference Between Seasoned and Unseasoned
Wood - Manner of Evaporation of Water - Absorption of Water
by Dry Wood - Rapidity of Evaporation - Physical Properties
that Influence Drying 119-127



Advantages of Seasoning - Prevention of Checking and
Splitting - Shrinkage of Wood - Expansion of Wood - Elimination of
Stain and Mildew 128-137



Difficulties of Drying Wood - Changes Rendering Drying
Difficult - Losses Due to Improper Kiln-drying - Properties of
Wood that Effect Drying - Unsolved Problems in Kiln-drying 138-144



Methods of Drying - Drying at Atmospheric Pressure - Drying Under
Pressure and Vacuum - Impregnation Methods - Preliminary
Treatments - Out-of-door Seasoning 145-155



Advantages of Kiln-drying over Air Drying - Physical Conditions
Governing the Drying of Wood - Theory of Kiln-drying - Requirements
in a Satisfactory Dry Kiln - Kiln-drying - Remarks - Underlying
Principles - Objects of Kiln-drying - Conditions of Success - Different
Treatments According to Kind - Temperature Depends - Air
Circulation - Humidity - Kiln-drying - Pounds of Water Lost in Drying
100 Pounds of Green Wood in the Kiln - Kiln-drying Gum - Preliminary
Steaming - Final Steaming - Kiln-drying of Green Red Gum 156-184



Different types of Dry Kilns - The "Blower" or "Hot Blast" Dry
Kiln - Operating the "Blower" or "Hot Blast" Dry Kiln - The
"Pipe" or "Moist-Air" Dry Kiln - Operating the "Pipe" or
"Moist-Air" Dry Kiln - Choice of Drying Method - Kilns of
Different Types - The "Progressive" Dry Kiln - The "Apartment"
Dry Kiln - The "Pocket" Dry Kiln - The "Tower" Dry Kiln - The
"Box" Dry Kiln 185-205



Kiln Cars and Method of Loading Same - The "Cross-wise" Piling
Method - The "End-wise" Piling Method - The "Edge-wise"
Piling Method - The Automatic Lumber Stacker - The Unstacker
Car - Stave Piling - Shingle Piling - Stave Bolt Trucks - Different
Types of Kiln Cars - Different Types of Transfer Cars - Dry Kiln
Doors - Different Types of Kiln Door Carriers 206-236



The Humidity Diagram - Examples of Use - The Hygrodeik - The
Recording Hygrometer - The Registering Hygrometer - The
Recording Thermometer - The Registering Thermometer - The
Recording Steam Gauge - The Troemroid Scalometer - Test
Samples - Weighing - Examples of Use - Records of Moisture
Content - Saw Mills - Factories - The Electric Heater 237-250


Bibliography - Glossary - Index of Latin Names - Index of Common
Names 251-257



1. Board of pine 13
2. Wood of spruce 14
3. Group of fibres from pine wood 15
4. Block of oak 31
5. Board of oak 32
6. Cross-section of oak highly magnified 32
7. Highly magnified fibres of wood 33
8. Isolated fibres and cells of wood 34
9. Cross-section of basswood 35
10. A large red gum 52
11. A tupelo gum slough 53
12. Second growth red gum 57
13. A cypress slough in dry season 58
14. A large cottonwood 78
15. Spiral grain in wood 87
16. Alternating spiral grain in cypress 87
17. Wavy grain in beech 88
18. Section of wood showing position of the grain at base of limb 89
19. Cross-section of a group of wood fibres 91
20. Isolated fibres of wood 91
21. Orientation of wood samples 93
22. Work of ambrosia beetles in tulip or yellow poplar 100
23. Work of ambrosia beetles in oak 100
24. Work of round-headed and flat-headed borers in pine 102
25. Work of timber worms in oak 103
26. Work of powder post borers in hickory poles 104
27. Work of powder post borers in hickory poles 104
28. Work of powder post borers in hickory handles 105
29. Work of round-headed borers in white pine staves 111
30. U. S. Forest Service humidity controlled dry kiln 161
31. Section through moist-air dry kiln 189
32. Live steam single pipe heating apparatus 190
33. Live steam double pipe heating apparatus 191
34. Vertical Pipe heating apparatus 193
35. Progressive dry kilns 197
36. Apartment dry kilns 199
37. Pocket dry kilns 201
38. Tower dry kiln 203
39. Box dry kiln 205
40. Edge-wise method of piling 206
41. Edge-wise method of piling 207
42. Automatic lumber stacker 208
43. Automatic lumber stacker 208
44. Battery of three automatic lumber stackers 209
45. Battery of three automatic lumber stackers 209
46. Lumber loaded edge-wise on kiln truck 210
47. The lumber unstacker 211
48. The lumber unstacker car 211
49. Method of piling veneer on edge 212
50. Kiln truck loaded cross-wise of kiln 213
51. Kiln truck loaded cross-wise of kiln 214
52. Kiln truck loaded end-wise of kiln 214
53. Kiln truck loaded end-wise of kiln 215
54. Method of piling staves on kiln truck 216
55. Method of piling staves on kiln truck 216
56. Method of piling tub or pail staves on kiln truck 217
57. Method of piling bundled staves on kiln truck 217
58. Method of piling shingles on kiln truck 218
59. Method of piling shingles on kiln truck 218
60. Method of piling shingles on kiln truck 219
61. Kiln truck designed for loose pail staves 219
62. Kiln truck designed for handling short stock 221
63. Stave bolt truck 221
64. Stave bolt truck 222
65. Stave bolt truck 222
66. Stave bolt truck 223
67. Stave bolt truck 223
68. Stave bolt truck 224
69. Regular 3-rail transfer car 224
70. Regular 3-rail transfer car 225
71. Special 4-rail transfer car 225
72. Regular 2-rail transfer car 225
73. Regular 2-rail transfer car 226
74. Underslung type 3-rail transfer car 226
75. Underslung type 2-rail transfer car 226
76. Flexible type 2-rail transfer car 227
77. Regular transfer car for stave bolt trucks 228
78. Regular transfer car for stave bolt trucks 228
79. Special transfer car for stave bolt trucks 228
80. Regular channel iron kiln truck for cross-wise piling 229
81. Regular channel iron kiln truck for cross-wise piling 229
82. Regular channel iron kiln truck for end-wise piling 230
83. Special channel iron kiln truck for end-wise piling 230
84. Regular dolly kiln truck for end-wise piling 230
85. Asbestos-lined kiln door 231
86. Twin door carrier with door loaded 232
87. Twin door carrier for doors 18 to 35 feet wide 232
88. Kiln door carrier 233
89. Kiln door construction 234
90. Kiln door construction 235
91. Kiln door construction 235
92. Kiln door construction 236
93. The Humidity diagram _facing_ 237
94. The hygrodeik 242
95. The recording hygrometer 243
96. The registering hygrometer 244
97. The recording thermometer 245
98. The registering thermometer 246
99. The recording steam gauge 246
100. The troemroid scalometer 247
101. The electric heater 250




Characteristics and Properties

Timber was probably one of the earliest, if not the earliest, of
materials used by man for constructional purposes. With it he built
for himself a shelter from the elements; it provided him with fuel and
oft-times food, and the tree cut down and let across a stream formed
the first bridge. From it, too, he made his "dug-out" to travel along
and across the rivers of the district in which he dwelt; so on down
through the ages, for shipbuilding and constructive purposes, timber
has continued to our own time to be one of the most largely used of
nature's products.

Although wood has been in use so long and so universally, there still
exists a remarkable lack of knowledge regarding its nature, not only
among ordinary workmen, but among those who might be expected to know
its properties. Consequently it is often used in a faulty and wasteful
manner. Experience has been almost the only teacher, and
theories - sometimes right, sometimes wrong - rather than well
substantiated facts, lead the workman.

One reason for this imperfect knowledge lies in the fact that wood is
not a homogeneous material, but a complicated structure, and so
variable, that one piece will behave very differently from another,
although cut from the same tree. Not only does the wood of one species
differ from that of another, but the butt cut differs from that of the
top log, the heartwood from the sapwood; the wood of quickly-grown
sapling of the abandoned field, from that of the slowly-grown, old
monarch of the forest. Even the manner in which the tree was cut and
kept influences its behavior and quality. It is therefore extremely
difficult to study the material for the purpose of establishing
general laws.

The experienced woodsman will look for straight-grained, long-fibred
woods, with the absence of disturbing resinous and coloring matter,
knots, etc., and will quickly distinguish the more porous red or black
oaks from the less porous white species, _Quercus alba_. That the
inspection should have regard to defects and unhealthy conditions
(often indicated by color) goes without saying, and such inspection is
usually practised. That knots, even the smallest, are defects, which
for some uses condemn the material entirely, need hardly be mentioned.
But that "season-checks," even those that have closed by subsequent
shrinkage, remain elements of weakness is not so readily appreciated;
yet there cannot be any doubt of this, since these, the intimate
connections of the wood fibres, when once interrupted are never

Careful woods-foremen and manufacturers, therefore, are concerned as
to the manner in which their timber is treated after the felling, for,
according to the more or less careful seasoning of it, the season
checks - not altogether avoidable - are more or less abundant.

There is no country where wood is more lavishly used or criminally
neglected than in the United States, and none in which nature has more
bountifully provided for all reasonable requirements.

In the absence of proper efforts to secure reproduction, the most
valuable kinds are rapidly being decimated, and the necessity of a
more rational and careful use of what remains is clearly apparent. By
greater care in selection, however, not only will the duration of the
supply be extended, but more satisfactory results will accrue from its

There are few more extensive and wide-reaching subjects on which to
treat than timber, which in this book refers to dead timber - the
timber of commerce - as distinct from the living tree. Such a great
number of different kinds of wood are now being brought from various
parts of the world, so many new kinds are continually being added, and
the subject is more difficult to explain because timber of practically
the same character which comes from different localities goes under
different names, that if one were always to adhere to the botanical
name there would be less confusion, although even botanists differ in
some cases as to names. Except in the cases of the older and better
known timbers, one rarely takes up two books dealing with timber and
finds the botanical names the same; moreover, trees of the same
species may produce a much poorer quality of timber when obtained from
different localities in the same country, so that botanical knowledge
will not always allow us to dispense with other tests.

The structure of wood affords the only reliable means of
distinguishing the different kinds. Color, weight, smell, and other
appearances, which are often direct or indirect results of structure,
may be helpful in this distinction, but cannot be relied upon
entirely. Furthermore, structure underlies nearly all the technical
properties of this important product, and furnishes an explanation why
one piece differs in these properties from another. Structure explains
why oak is heavier, stronger, and tougher than pine; why it is harder
to saw and plane, and why it is so much more difficult to season
without injury. From its less porous structure alone it is evident
that a piece of young and thrifty oak is stronger than the porous wood
of an old or stunted tree, or that a Georgia or long-leaf pine excels
white pine in weight and strength.

Keeping especially in mind the arrangement and direction of the fibres
of wood, it is clear at once why knots and "cross-grain" interfere
with the strength of timber. It is due to the structural peculiarities
that "honeycombing" occurs in rapid seasoning, that checks or cracks
extend radially and follow pith rays, that tangent or "bastard" cut
stock shrinks and warps more than that which is quarter-sawn. These
same peculiarities enable oak to take a better finish than basswood or
coarse-grained pine.

Structure of Wood

The softwoods are made up chiefly of tracheids, or vertical cells
closed at the ends, and of the relatively short parenchyma cells of
the medullary rays which extend radially from the heart of the tree.
The course of the tracheids and the rays are at right angles to each
other. Although the tracheids have their permeable portions or pits in
their walls, liquids cannot pass through them with the greatest ease.
The softwoods do not contain "pores" or vessels and are therefore
called "non-porous" woods.

The hardwoods are not so simple in structure as softwoods. They
contain not only rays, and in many cases tracheids, but also
thick-walled cells called fibres and wood parenchyma for the storage
of such foods as starches and sugars. The principal structural
features of the hardwoods are the pores or vessels. These are long
tubes, the segments of which are made up of cells which have lost
their end walls and joined end to end, forming continuous "pipe lines"
from the roots to the leaves in the tree. Since they possess pores or
vessels, the hardwoods are called "porous" woods.

Red oak is an excellent example of a porous wood. In white oak the
vessels of the heartwood especially are closed, very generally by
ingrowths called tyloses. This probably explains why red oak dries
more easily and rapidly than white oak.

The red and black gums are perhaps the simplest of the hardwoods in
structure. They are termed "diffuse porous" woods because of the
numerous scattered pores they contain. They have only vessels, wood
fibres, and a few parenchyma cells. The medullary rays, although
present, are scarcely visible in most instances. The vessels are in
many cases open, and might be expected to offer relatively little
resistance to drying.

Properties of Wood

Certain general properties of wood may be discussed briefly. We know

Online LibraryJ. B. (Joseph Bernard) WagnerSeasoning of Wood → online text (page 1 of 24)