46 
BULLETIN 1500, U. S. DEPARTMENT OF AGRICULTURE 
joint conditions but with the same grade of glue as used in Figure 14, 
where the joints were made under good conditions. In comparing 
Figure 16 with Figure 14 it may be observed that in the joints of 
most of the nonporous woods the shear strength and the percentage 
of wood failure remain almost the same for both the starved and 
good gluing conditions, however, in the joints of most of the porous 
woods the shear strength and the percentage wood failure differ 
greatly. 
Sapwood is generally more porous and contains less gums, oils, 
resins, tannin, or other infiltrated material than heartwood. The 
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1200 1600 2000 2400 2800 3200 3600 4000 
Shear ma Strength — Lbs per Sa. In. 
t- Alder, red 
22-Hemlock, western 
2-Ash, white (comt 
23- Hickory 
3-Basswood 
24- Maynolia 
4-Beech 
25 - Mah oaantf 
5-Bi>*ch, uel/ow 
26-Mople, soft (com/J 
6-Butternut 
ri-Mop/e, suaar 
1 -Cedar. Alaska 
23- Oak, red (com- 1.) 
8-Cedar, eastern 
rea- 
29- Oak, white (conffj 
9- Cedar western 
red 
30-Osaae -oronae 
31-Pecan 
10-Cherra. black 
//-Ches/nuf 
32- Persimmon 
/2-Cot ion wood 
33-Pine, nor-thern white 
/3-Cypress, southern 
34-Pine, southern yellov\ 
14-flm, American 
3S-f => ine t western ueJiow 
IS-BIm, rock 
36-f D oplar, yet tow 
16-PoaaIas fir 
n-Fir. white 
37-Kedwood 
38-Sas^sa fras 
I8-Gum. black (con 
'/.) 
39-o~pruce, Sitka 
I9-Gwm, red (heorfwood) 40-Sycamore 
20-Gum, red (sapwood) 
41-Wa/hut, black 
26-Gum, fupelo (cot 
nV 
Specific Gravity of Wood 
Figure 15. — Relation of density of wood to the shear strength and wood failure of 
glued joints. Averaged results with animal, casein, and vegetable glues given 
in Figures 12, 13, and 14 
results for many of the species given in Figures 12, 13, 14, and 16 
were obtained on glued combinations of heartwood and sapwood. 
In Table 4 the results of special tests on heartwood and on sapwood 
are shown for nine species which were glued with animal, casein, and 
vegetable glue, respectively. The results for the heartwood and the 
sapwood of some species are as different as the results between some 
distinct species. Infiltrated materials in the woods used for these 
tests, especially in the red gum and in the black walnut, interfered 
with the glue adhesion. Tests made on the various woods which 
were not previously treated to curtail the interference on infiltrated 
materials on the glue adhesion gave varied results with different glues. 
For example, the heartwood of eastern red cedar glued satisfac- 
torily when the casein and the vegetable glues were used, but glued 
unsatisfactorily when the animal glue was used, The free alkali of 
