The mirror., 1919-09-25
"A Wood Stronger than Steel
Continued from page il

[Continued from page II
tion Of the plies. Soaking in cold water
for 10 days gave the same result.
The blocks were tested in shearing ma.
chine. which applied force in such man
ncr as to push one ply from another. In
this test pressure of from $50 to 700 lbs.
to the square inch of glue surface was re-
quired to separate the layers, so strong
were the new CLUES, and even then it was. in
most cases, not the glue, but the wood f.
bers themselves, that gave way. After
boiling the test pieces for eight hours, the
average pressure exerted amounted to 1870
lbs., and after soaking them for 10 days the
plies de6ed pressure up.to 200 lbs. Since
the specifications for airplane plywood de-
.manded only that the material exhibit a
strength sufficient to withstand pressure of
$50 lbs. to the square inch when dry, the
new CLUES were accepted with acclaim. AL
so, as an added feature, it was demonstrated
thar, after drying again, the blood glue re-
gained all but six per cent of its original
strength, while the casein glue lost only 1S
pei cent in the tests, which, of course, were
much more severe than any conditions a
service airplane would ever be called upon
to withstand.
In the case of thicker joints-blood glue
is used only for veneer, where it can be
pressed by steam heated plates-the new
casein glue exhibited remarkable strength.
With blocks OF maple having the grain
running in the same direction, shearing
strength of from 1000 to $500 lbs. to the
square inch was found to be common.
These new CLUES saved the government
over $6, 600, 900 in the construction of ply
wood alone. As in the case with all the
discoveries of the Forest Products Labora-
tory not actually needed exclusively for war,
the formulas are at the service of American
industry. Any manufacturer or private
user of CLUES who wishes to manufacture
either of these CLUES is at liberty to do so.
The laboratory will give advice in this res
pect, and extend experimental help if this
is necessary,
In considering the application of this
new waterproof glue and plywood to in
dustry in our reconstruction period, it be-
comes evident that an entirely new field
has opened for progressive manufacturers
of wood articles. Who, till now, has put
on the market standard door that will not
warpl Plywood panels cannot warp after
they are finished, for one ply holds the
next rigidly. What manufacturer has got
out table or chair with glued joints that
will not fall to pieces in a damp atmos-
sphere? Furniture made with casein glue
will hold together far better.
For cabinetmakers and manufacturers of
wall coverings another entirely new aspect
appears. The 1.4O in. plywood used as
covering for airplane wings naturally re-
tains every beauty and quality of the wood
the case of mahogany, Circassian walnut,
and other fine varieties, of taking just as
high polish as the thicker veneers used by
the trade until this year. Ponder this: The
thin plywood will not warp or peel; it can
be manufactured from the finest walnut at
total cost of less than three cents square
foot, while for cheaper woods the cost runs
in the neighborhood of one cent a foot.
This is between one-third and one-tenth the
cost of ordinary veneers used for cabinet
making or for wall paneling. 1t is so in
expensive that the finished product could
be retailed at price within the reach of
the great majority of house owners.
Thousands of them, now content with for
id wall papers, would use the new plywood
paneling. What manufacturer wants the
chance to be first in the 6eldl