Thermally-Modified Ash Wood

Thermally-Modified Ash Wood

Thermo ash - dark and resistant

Thermo ash is a heat-treated ash with a chocolate-coloured tint throughout. For production, the ash wood is heated to temperatures of more than 160° C (≈ 320°F) for 24 to 48 hours under oxygen deprivation. Depending on the height and duration of the temperature development, the woods change colour from a light light brown to dark brown.

The thermal treatment increases the rot resistance of the wood. It also reduces the water absorption capacity, which in turn minimises the tendency to swell, shrink and cup and protects the wood from fungal attack. But there is a negative development in the susceptibility to longitudinal cracks, e.g. when drilling and screwing in screws. Therefore, the holes must always be pre-drilled during assembly!

ALVARO storage box with thermal ash seat rest
Storage box ALVARO, covered with dark brown thermo ash

Standard dimensions for thermo-ash seat rests

The classic use of thermo-ash is as decking boards. For this reason, particularly flat formats are readily available. We have chosen 25 mm x 120 mm as the standard dimension in stock. This can be used to create visually harmonious bench tops with a total width of approx. 500 mm (4x plank with width 120 mm + intermediate spacing). Other dimensions for your custom-made products are possible by arrangement.

Thermo ash seat rest
Thermo ash with standard dimension 25 mm x 120 mm

Thermo ash is a natural product - with all its advantages and disadvantages

If you choose thermo-ash as a surface for your bench, your garden furniture or your storage box, you must be aware that wood is a natural product – with all its advantages and disadvantages. Warping, colour differences, cracks, stone inclusions and other irregularities are part of this renewable raw material. So surface cracks are normal and tension cracks are possible even with thermally treated wood. A normal width is 1-3 mm and the length can vary. Stress cracks mainly happen along the front, where the water intake and water release is higher. Note: Cracks are no reason for complaints.

Colour differences are a natural feature of the renewable raw material due to the inhomogeneous nature of the wood and different growth areas, as is the natural onset of wood greying. But neither of these influences the durability of the seat surfaces.

Oiling as a remedy against greying of wood

Without oiling, any wood – including thermally treated ash – will turn grey within a few months and take on the silvery appearance typical of wood. Thermo ash has an average lifespan of up to 20 years in a moderate climate. This is not significantly prolonged by oiling. The only purpose of oiling is to delay the greying of the wood. To delay this effect, the surface should be treated once or twice a year.

We recommend the viscous linseed oil varnish for oiling. To produce linseed oil varnish, linseed oil is boiled under exclusion of air, which changes its consistency. Both oils have been used for centuries as natural wood preservatives. To ensure that the oil penetrates as deeply as possible into the wood, we recommend diluting this varnish with turpentine oil and applying it several times if necessary. The hardening of the oil is faster than with pure, cold-pressed linseed oil but can take a few days. Attention: For seat rests delivered ex works, check before first use whether the protective oil has already dried completely! The oil closes the pores of the wood so that dirt cannot stick immediately and makes cleaning easier afterwards.

Thermoesche vergraut als Beispiel
Thermo ash will also turn grey within a few months without treatment.
Attention

If you do not want the above-mentioned features on your high-quality garden objects, we recommend that you choose industrially manufactured seat covers made of RESYSTA®, KEBONY® or black plastic. We are happy to share our experience with you if you wish to have an alternative to wood. An alternative that guarantees perfect, constant, industrially manufactured quality.

Tender text for GaLaBau, for landscape architects and planners

“Thermally-modified ash wood, chamber-dried, residual moisture under 20%. Surface planed and sanded on all sides, all edges beveled 2 x 45°. Surface sliqutly oiled.”

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