Kaarna (Bark)
Kaarna reflects the warm brown hues of a rugged surface. The shade evokes the heart of the forest and the beauty of nature.
Applications
Manufacturing
Kaarna product is made by charring the wood surface at over 1000 °C using Hiil's charring technology. After charring, the product is pressure-washed, brushed, dried and oiled with clear special linseed oil. The oil adds protection, alters the char surface structure and binds the carbon into the wood.
Specifications
| Surface | Charred, washed, brushed, oiled |
|---|---|
| Wood species | Pine, Kiertopuu® pine |
| Wood certification | PEFC certified |
| Standard sizes | |
| Panel | 26 mm Widths 118, 143, 193 mm Lengths 4110, 5030 mm, end-matched Exterior / interior cladding Coverage −10 mm from the width  |
| Board | 26 mm Widths 118, 143, 168, 193 mm Lengths 4200, 5100 mm Decking  |
| Plank | 43 mm Widths 143, 193 mm Lengths 4200, 5100 mm Decking |
| Country of origin | Finland |
| CE marking | Product is CE marked |
| Fire class | D class B-class when treated with fire retardant, spruce as material. |
Indicative lead time for the standard range is about 5 weeks from order. Check availability for each product.
Outside the standard range, products can be made to order in thicknesses 20–43 mm, widths 93–193 mm and lengths 2000–6000 mm. Price and lead time are quoted case by case.
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Weather exposure
Weather exposure test for Hiil Oy charred wood products
Natural Resources Institute Finland - 27 March 2025 results - Veikko Möttönen and Nina Pottonen.
Weather exposure test programme: 102 min UV exposure and 18 min UV+rain exposure, repeated over 6 weeks (1008 h). Equivalence: The treatment can be considered to correspond to approximately 3 years of outdoor exposure to rain and sunlight. UV radiation dose in the test was approximately 218 MJ/m².
Installation and maintenance guides
Downloads
Find more on the Resources page.
Example projects using Kaarna
Beautifully greying charred terrace
An uncovered terrace of about twenty square metres in Kelo decking, with Kaarna posts, beside a compact house in the woods – evenly grey in less than a year.
Halo Igloos Resort – Northern lights and charred wood
Halo Igloos is a glass igloo resort in Rovaniemi where Hiil Kiertopuu products bring an ecological dimension both outdoors and indoors.
AITO Saunas’ charred wood cladding
AITO Sauna builds saunas where Finnish design meets everyday wellbeing. Hiil has supplied charred wood surfaces to AITO projects in Ibiza and beyond.
Charred roof terrace
Design studio Amerikka’s new office roof terrace with Kaarna decking – charred, brushed, and oiled surface.