University of Wisconsin Digital Collections
Link to University of Wisconsin Digital Collections
Link to University of Wisconsin Digital Collections
The State of Wisconsin Collection

Page View

Northrop, E. B.; Chittenden, H. A., Jr. (ed.) / The Wisconsin lumberman, devoted to the lumbering interests of the northwest
(July, 1874)

Classification of wood,   pp. 393-397 PDF (1.8 MB)


Page 395


lhe Wisconsin Lumbeman.
if possible, from sunshine and high
winds. The seasoning yard should
be paved and well drained, and tim-
ber supported on stone of cast-iorn
bearers, and piled so as to admit of
the free circulation of air over all
the surfaces of the pieces.
Natural seasoning to fit timber for
.carpenters' work usually occupies
about two years; for joiners' work
and machinery, about four years; but
much longer periods are sometimes
employed.
To steep timber in water for a
fortnight after felling it, extracts
parts of the sap, and makes the dry-
ing process more rapid.
Artificial Seasoning consist in dry-
ing the timber in an oven by means
of a current of hot air. It occupies
from seven or nine days for each
inch of the thickness of the piece of
timber.
In the course of drying, timber
loses weight and shrinks in its
transverse dimensions. The loss of
weight ranges in different examples
from 6 per cent. to 40 per cent.; and
the transverse shrinking from 2 per
cent. to 8 per cent., the most common
rate being 3 per cent. The sorts of
wood which shrink most in drying
are the most subject to warp.
DuRABiLrry, DECAY, EjD PRESERVA-
TION OF WOOD.-All kinds of timber
are most lasting when kept constant-
ly dry, and at the same time freely
ventilated.
Timber kept constantly wet is
softened and weakened; but it does
not necessarily decay. Various kinds
of timber, some of which have been
already mentioned, such as green-
heart, elm and beech, possess great
durability in that condition.
The situation which is least favor-
able to the duration of timber is that
of alternate wetness and dryness, or
of a slight .degree of moisture, es-
pecially if accompanied by heat and
-confined air.
Timber exposed to confined air
alone, without the presence of any
considerable quantity of moisture,
decays by "dry rot," which is accom-
panied by the growth of a fungus,
and finally converts the wood into a
fine powder.
Amongst the most efficient means
of preserving wood, are good sea-
soning and the free circulation of
air.
Protection against moisture is af-
forded by oil paint, provided that
the timber is perfectly dry when first
painted, and that the paint is re-
newed from time to time. A coating
of pitch or tar may be used for the
same purpose.
Protection against the dry rot
may be obtained by saturating the
timber with solutions of metallic
salts, such as sulphate of iron, sul-
phate of copper, bichloride of mer-
cury, and chloride of zinc.
Timber is protected against wet
rot, dry rot, and white ants, by satu-
ration with the liquid called com-
mercially "creosote," which is a kind
of pitch oil.
STRENGTH OF TiXBEB. - Amongst
different specimens of timber of the
same species, those which are most
dense in the dry state are in general
also the strongest.
Tables of the results of experi-
ments on the strength of different
kinds of timber, strained in various
ways, will be given hereafter.
The following are some general re-
marks as to the different ways in
which the strength of timber is
exerted:
I The Tenacity along the grain, de-
pending, as it does, on the tenacity
of the fibres of the vascular tissue, is
on the whole greatest in those kinds
and pieces of wood in which those
fibres are straightest and most dis-
tinctly marked. It is not materially
affected by temporary wetness of the
timber, but is diminished by long-
continued saturation with water, and
by steaming and boiling.
The Tenacity across the grain, de-
pending chiefly on the lateral adhes-
ion of the fibres, is always consider-
ably less than the tenacity along the
.II
.   I ,.-
I'
396


Go up to Top of Page