Kebony

Overview

Kebony is softwood pine impregnated with furfuryl alcohol, then cured with pressure, vacuum and heat so the liquid becomes a furan resin inside the cell walls. The product looks like a deep brown hardwood and is sold mainly as decking and cladding. People choose it when they want a harder, more stable alternative to tropical decking. Hardness, warranty and lifespan figures in this entry come from the maker, its distributors and a reseller, so read them as manufacturer claims.

Pros

• Hard for a pine: the maker's spec sheet (via Hewn) gives Janka 7.2 kN, about 1,619 lbf, and DesignOneSource states 1,618 lbf. Both are manufacturer figures.
• Stable. In Accsys's own comparison table (Accsys makes Accoya, a competitor) Kebony shrinks 1.4% radial and 2.5% tangential, better than thermally modified ash.
• Improved decay and insect resistance and hardness, per Wikipedia's furfuryl alcohol page.
• 30-year warranty and a 50-75-year life claim at DesignOneSource; the HITSA guide estimates a life of up to 30 years, so these claims do not agree.
• The resin comes from a plant-based by-product (corncobs and sugar cane bagasse), per Wikipedia.

Cons

• Priced at around $15-17 per board foot equivalent, so budget for it as a premium decking.
• Shrinkage cracks can still appear like other wood (HITSA guide).
• Flame spread class B (ASTM E84, flame spread 65, smoke 300; Hewn spec sheet).
• The deep brown fades to silver-grey unless you oil it with a pigmented oil (HITSA).
• Thickness is confusing: Hewn lists 5/4x6 as actual 3/4 in by 5 1/2 in, while Dunn Lumber states 7/8 in; check the actual size before designing.

Variants and subspecies

• Kebony Clear is Pinus radiata, density 670 kg/m3 (HITSA guide).
• Kebony Character is Pinus sylvestris (Scots pine), density 490 kg/m3 (HITSA guide). It is a different base wood, so the Clear hardness figure above should not be assumed for it; I found no Janka for Character.
• Related modification chemistries: acetylated wood (Accoya) and thermally modified wood.

Working and finishing

Hewn lists moisture content at 4-8%. Boards are sold pre-sanded in 10-16 ft lengths (DesignOneSource). Fixings and glue guidance should come from the Kebony installation instructions; I did not find a sourced fastener rule in the pages I read, so I make no claim. Clean with a brush and water, and use oxalic-acid cleaners for stains (HITSA).

Staining and finishing colour

The wood is deep brown from the maker, so staining is rarely the point. The HITSA guide says to oil with a pigmented oil to keep the colour, or leave it to patina to silver-grey. I found no tests of conventional stains on Kebony.

Sustainability and handling

Wikipedia says Kebony uses FSC/PEFC-certified wood and the Norwegian company, formerly Wood Polymer Technologies (1996) and renamed in 2007, makes it. Furfuryl alcohol is made by hydrogenating furfural from corncobs and sugar cane bagasse and is described as a green chemical (Wikipedia). The same page links to health-hazard references for the raw liquid (CDC NIOSH); I did not check what they say about the cured wood, so treat the dust as ordinary wood dust and ask the maker for a safety sheet.

Popular projects

Decking and cladding first; also cabinets and interior walls (DesignOneSource), and outdoor furniture where a hard brown surface is wanted.

Buying notes

Sold as 5/4x6 grooved decking in 10-16 ft lengths, priced per linear foot (Dunn Lumber: $9.68 per lf; Capitol City: $16.59 list, $11.79 sale, unit not stated). Convert to board feet before comparing with hardwoods. Buy Clear or Character deliberately, and ask for the batch's thickness.