CONTRIBUTORS- WOOD WORKS
HERE IS SOME ADDITIONAL INFORMATION ON THE PROPERTIES OF RED IVORY FOR THE WOOD ENTHUSIAST:
RED IVORY: HARD FACTS
Botanical / scientific name:
Trade name:
Berchemia zeyheri( Family: Rhamnaceae)
Red Ivory( Other names: Pink Ivory, Mutiwenkosi, umNini, Pau-rosa( Mozambique)
Origin:
Conservation status:
Bole characteristics:
South Africa, Swaziland, Mozambique and Botswana. The species occurs in open woodland,
Not endangered or protected.
A shrub to small tree, up to 10m in height. Large, straight logs are very difficult to find. often on termite mounds, on rocky ridges and along watercourses.
The stems are often divided or short and badly shaped.
Colour: The heartwood is pale pink to deep red. The yellowish sapwood is clearly defined. Grain pattern:
Density( at 12 % moisture content):
Strength / bending properties:
Seasoning:
Durability and preservative treatment:
Working and finishing properties:
Straight to interlocked. The texture is very fine and even.
The air-dry density ranges from 990 to 1 100kg / m 3, with an average of 1 040kg / m 3.
The wood seasons slowly, with 25mm boards taking up to a year to air-dry. Surface checking and end splitting will occur if boards are exposed to the
The wood seasons well, but rather slowly with very little shrinkage.
The wood is very durable and resistant to borer and fungi.
The wood saws quite easily despite its hardness. Tungsten-tipped saw teeth are recommended. Wet wood has an unpleasant,‘ damp’ smell when being milled. Boards without interlocked or wavy grain plane well to a smooth finish. When sanding, the sandpaper tends to clog up quickly.
The wood is not lustrous and has no characteristic odour.
sun and drying under cover is essential to minimise this. Kiln-drying schedule 1 is recommended( see below).
Both air- and kiln-drying can be done with no or very slight drying defects and once dry, the timber is remarkably stable in use.
It is extremely resistant to preservative treatment.
The wood takes paint and varnish well. Varnishes containing ultra-violet filters are recommended to preserve the heartwood colour and prevent it from turning brown. The bark and sap are reported to be irritants and may cause dermatitis and poisoning.
TIMBER DRYING SCHEDULE FOR RED IVORY( Berchemia zeyheri) Supplied by H-P Stöhr, Timber Drying Institute( timberdrying @ mweb. co. za)
Dry Bulb temperatures(° C) and Relative Humidity(%) at the following Timber Moisture Contents
Drying schedule no.
Green 40 % 30 % 18 % to final DB RH % DB RH % DB RH % DB RH %
1 35 77 40 65 45 53 60 32
DB = Dry bulb temperature, RH = Relative Humidity Please note: Drying schedules only serve as a guide to the kiln operator, with the response of the timber to the drying condition being the criterion.
REFERENCES AND SOURCES
1. Coates-Palgrave, M. 2002. Keith Coates-Palgrave Trees of Southern Africa, Random House Struik, Cape Town. 2. Dyer, S, James, B and James, D. 2016. Guide to the Properties and Uses of Southern African Wood. Briza Publishers, Pretoria. 3. Flynn, JH and Holder, CD( ed.) 2001. A Guide to Useful Woods of the World. Forest Products Society, Madison, WI.
58 APRIL / MAY 2017 //