Sr 
SCIENCE AND INDUSTRY. 
For more than a dozen years I have watched a process of ‘building 
up ply-stock by a vegetable adhesive which has largely displaced animal 
gelatine. The devélopment has been chiefly by experiment, for chemical 
analysis shows no difference between successful and unsuccessful kinds 
of this adhesive, and there has been consequently much loss of time, 
besides waste and disappointrnent when departures were made from 
proved substances. We believe that the one reliable preparation is 
made from cassava-root, and that other kinds of starch have given un- 
satisfactory results. I have often inspected the apparatus for glueing, 
which is much simpler, and the methods of handling much less exacting 
than those we are compelled to follow in dealing with gelatines. 
Kneaded in a particular way, and treated with alkali in the prescribed 
manner, this vegetable glue is tested as to viscosity by being drawn into 
threads whose tenuity is remarkable. The filaments are finer than those 
of a spider’s web, we are told, and so indeed they appear. Were it 
possible to examine the molecules it would be an interesting study to 
find out and display what are the qualities which permit of such 
amazing cohesion. What can be the attraction that holds them together? 
At all events, being of vegetable origin, the fibres of the sheets of veneer 
are joined by a substance almost homogeneous with their own, and thus 
the processes of polishing are less likely to be spoiled than when a 
heterogeneous substance, as gelatine, is used. In both cases the adhesive 
penetrates the’ pores of all end-grain, of which, as already stated, figured 
ornament chiefly consists. Gelatine is not a suitable base for any 
polish, whereas the starch in a specially chosen form as just described 
is an approximation to wood-fibre, and probably for that reason does 
not cause the troubles which so often arise from gelatine. The tenacity 
of this adhesive is great when applied to sheets, and although it is 
sometimes applied to main joints, that is, to joining lumber itself, the 
practice is as yet far from general. It is expected, however, that its 
use will be constantly extended. In both cases—vegetable and animal 
glue—the ply-stock is subjected to such pressure as just stops short of 
erushing the cores which are to be veneered. But with this difference 
that, whereas the cores and the glue in the case of gelatine must be 
kept at a warmth of about 160 deg. Fahrenheit by the use of heated 
cauls of metal, preferably zine or aluminium, the prepared starch is 
used cold, so that without risk the operation may be interrupted by the 
lunch hour, or indeed left over till next day. In effect the process is 
simpler, quicker, and in some respects more certain than the older 
method of using hot gelatine as an adhesive. There is no question as 
to the success of the system, and the only dangers introduced were when 
users stepped aside from knowledge that was adequately tested by 
practice, and rashly accepted quasi-scientific assurance that other sub- 
stances were essentially the same. There are many adhesives, each 
with its uses, but the two herein described are preponderant in wood- 
> working. © | ‘ 
Before leaving the subject of lumber and its joining there are char- 
acteristics of curious interest attaching to certain timbers. Some are 
so glassy or oily that ordinary glue will not attach them. Another can 
hardly be broken transversely, but under extreme strain will split or 
tear lengthwise. European beech will resist torsion. Walnut has the 
property of holding screws particularly well, and hence its special ap- 
plicability to gun stocks. A few woods are immune from the attacks 
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