What special features does Hemlock have as a material?Abbreviation DIN EN 13556
Tsuga heterophylla and Abies amabilis, family of the Pinaceae
west coast of North America, especially in Alaska, Brit. Columbia, Washington and Oregon.
Western Hemlock, Pacific Coast Hemlock, West Coast Hemlock, *Alaska Pine, Hembal
The wood, which in North America is known in its full name as Pacific Coast Hemlock, originally came only from the botanical species Tsuga heterophylla, a conifer related to native fir. Nowadays, however, the wood of the fir tree found in the same location is always added to the first mentioned species; both woods are so similar in appearance and technical properties that they can be used together.
Knotless lengths up to 30 m and diameters up to over 2 m, usually around 0.8 m, round and straight-edged; very old and strong trunks often with beginning rot in the inner trunk area. The dimensions for Amabilis Fir are only slightly smaller.
Color and structure
Sapwood around 2 cm wide, light grey to yellowish grey and hardly distinguishable from the usually only slightly darker interior, corresponding to a mature wood; the latter darkens in light, similar to spruce wood, slowly turning light yellowish brown. Partly with brown or light-grey stripes or grain, which, provided there is no fungal attack, have no influence on the technical quality.
Planed, dry wood shows an even matt shine on all surfaces. Pores are not present (softwood). Wood rays very small, only still visible as fine mirrors on radial surfaces. No resin channels. Annual rings on cross sections are clearly visible through the sharply defined light brown late wood on one side. It is usually narrower than the early wood of the same growth zone and, depending on the direction of cut, produces yellowish-brownish veins or striped structures, usually less distinct. Due to the often high age of the tree, the wood is often of a fine-grained structure with annual ring widths of less than 3 mm; extremely fine-grained wood is lighter and lighter. The grain is mainly straight, only occasionally wavy and leads to slightly offset late wood structures when cut lengthwise.
Light-coloured, straight grained and often fine-grained coniferous wood, similar to spruce wood with corresponding annual ring widths.
Isolated with brown bark inclusions running in the direction of the fibres, which are taken into account in the grading rules according to their size and number.
Artificial drying can be carried out without particular difficulties, despite the usually high initial moisture content. Hemlock belongs to the medium-heavy coniferous woods, similar to native spruce and pine wood. It can be easily processed with all tools with only a slight dullness, but requires well-sharpened tools and careful chip removal to achieve smooth planed surfaces, in order to avoid woolly surfaces or pressure marks caused by transport rollers. Durability is satisfactory; the wood is easy to glue, nail and screw. The absence of resin in the wood should be emphasized. When freshly saponified, it often has an unpleasant, acidic odor, which disappears during drying.
Hemlock is, similar to spruce, not sufficiently fungus-resistant to be permanent in moisture-exposed areas. Ferrous metals and alkalis cause dark discoloration of damp wood.
Hemlock is generally a good paint carrier and can be stained in all colours.
For this application area all forms of surface treatment can be used, especially transparent or colourless glazes, matting, waxes, varnishes and polishes.
Areas of application
Hemlock is used especially in surface-forming form in interior design, where, in addition to low weight, an even colouring and a clear but not too strongly emphasized wood structure are important. It has proven to be particularly suitable for acoustic, ceiling and wall coverings. Other uses are as blind and frame wood as well as for interior doors, panelling and built-in furniture. A special application is the construction of sauna rooms because of the absence of resin. Permanent use in weather-exposed exterior construction is only possible after application of wood preservatives with deep penetrating effect.
Apart from Tsuga heterophylla (= Western Hemlock), the species T. mertensiana (= Alpine Fir) is found in very high altitude and mostly already unused forests of western North America, and in eastern North America the species T. canadensis is widespread, whose usually smaller trunks provide a somewhat more strongly structured wood than Western Hemlock.
Western hemlock may contain, besides the fir wood of Abies amabilis, also that of A. grandis, the Western Balsam Fir or Grand Fir.
Hemlock - Technical properties
Weight fresh650 kg/m³
Weight air-dry510 kg/m³
Weight dry-dry470 kg/m³
Compressive strength u12-15 55 N/mm²
Flexural strength u12-15 83 N/mm²