Due to the relatively small diameter of the industrially used timber (on average 23-24 cm), the knot-free portion is rather small. The mean distance between larger knots is 60-70 cm, and rotten knots are quite frequent. This makes the production of knot-free timber longer than 1m considerably difficult.
Black locust is not easy to saw due to its hardness and strength characteristics; the cutting resistance (power requirement) is 20-30% greater than of oak and so the tool wear.
Timber does not require any special protection (e.g., spraying) on the log yard.
In the past few years, about 150 to 220 thousand m3 of black locust timber was annually converted to lumber in Hungary.
If properly steamed, the wood loses its unpleasant greenish-yellowish colour and gradually browns. After steaming, black locust wood can be machined more easily then before, and there will be less grain tear and splits. Black locust lumber is usually steamed in tight stacks immediately after sawing. Steaming is most efficient if it is carried through in pressurised cylinders (autoclaves), where the cycle lasts 20-30 hours at 110 °C.
Black locust can be properly steamed also in traditional steam chambers without saturating pressure. In this case the cycle lasts 60-180 hours. This method is milder, causes less cracking, and results in a lighter brown colour.
Locust is easy to dry (the schedules are similar to those of beech). The inherently low initial moisture content of timber is of great advantage. In our experience, if the wood was sawn up 1-1.5 months after felling, the net moisture content of the sawnwood was found to be 30-35% (50-60% with oak lumber).
Accordingly, black locust lumber, floor and furniture material can be kiln dried right after sawing, and the sawn wood can be dried without the danger of quality loss, i.e. there is no need for pre-drying.
Steam-softened wood bends well for furniture parts.
With black locust, machining tools have to be replaced more frequently when compared with other, more commonly used species (oak, beech).
Black locust can be properly bonded with the usual glues and bonding techniques. However, the specific features of black locust (e.g., clogged pores) have to be taken into consideration when choosing bonding parameters.
The usual surface treatment techniques apply to black locust. The variegated colour can be smoothened by proper priming and dyeing.