Some Tests on the Gluing Characteristics of Four \(/est Coast Hardwoods: Chinquapin, Tanoak, Calilornia Laurel, and Madrone

Bv \(. Z. Olson, Technolosist

U. S. Department of Agriculture

Some of the soft'ivood species of the Pacific Coast region have been utilized commercially to a great extent, rvhile irr. contrast, the hardrvoods used on a commercial scale in this area have been largely brought in from central and eastern areas of the United States even though the Pacific Coast has several native hardwood species. To promote closer utilization of hardwood species native to the area, the California Forest and Range Experiment Station has sponsored investigations of the properties of California laurel (Umbellularia Californica, best knor,vn to the novelty trade as Oregon myrtle), chinquapin (Castanopsis chrysophylla), tanoak (Lithocarpus dumosa), and madrone (Arbutus menziesii) to determine whether they are adaptable and satisfactory for commercial use. The U. S. Forest Products Laboratory rvas requested to assist in evaluating the characteristics of these species. Tests to determine their gluing characteristics rvere among those considered important. This report, therefore, presents results of tests to determine rvhether the four species can be satisfactorily glued lvith casein, starch, animal, urea, and resorcinol glues. As the amount of material available at the Laboratory from each species \vas limited, tl.re results may not be completely typical for each species, but they are probably inclicative of the quality of glued joints that may be expecte<i rvith these species under good gluing conditions.

The data in this report apply dircctly to laminating applications, in rvl-rich the tangential or radial surfaces of the Iumber are. glued, and the grain of adjacent pieces is in the same direction. In general, rvood in the form of veneer of the same species can be expected to give similar results rvhen glued into ply'ivood, in rvhich the grain of adjacent pieces is usually at right angles. It is believed, therefore, that none of these four species rvould invoh'e irlry ur-rusual gluing problem in making plywood. The initial dry-joint quality of such plywood would be expected to be in the same general order as shown in the present tests rvith the same glues.

All species were at about 8 per cent moisture content and were prepared lor gluing by cutting into 11/16- by 2i4- by l2-inch pieces. Four joints, each consisting of trvo pieces, were made with each species with each glue, except the laurel, for which only three joints could be made u.ith each glue because of lack of sufficient material.

The glue was applied to only one of the joining surfaces and the gluing conditions were as given in table 1. After being taken from the press, the joints rvere allorved to remain in an atmosphere at 80o F. and 3O per cent relative humidity for 1 week before block-shear-test specimens rvere cut. Five shear specimens n'ere cut from each joint and rvere tested dry in a universal-testing machine with the shearing head moving at a rate of about 0.015 inch per minute.

The average results of the shear tests of the joints are given in table 2. The data in table 2 indicate that California laurel offered some resistance to gluing rvith caseirr ancl vegetable glues, and that joints of inferior quality resulted in all four species rvhen animal glue rvas usecl under conditions favorable to starved joints. Horvever, good c1u:rlity joints u'ere obtained with all four specics rvhen animal glue was used under good gluing conditions. Joints made ir-r laurel lr'ith casein and vegetable glues and animal glue under good conditions l'ere adequate for many purposes, although percentages of rvood failure rvere lower than rvith most other hardrvood species listed in U. S' DeTd"intain"d at Madison, Wisc., in cooperation with the University of .Wisconsin.