Caring for RÅ Thermo Ash and Oak Chopping Boards in the Kitchen

Wooden kitchen tools last for years if they are washed, dried and oiled the right way, and they split or warp quickly if they are not. This guide covers the routine for Rosendahl's RÅ pieces in thermo ash and the Menageri board in oak: how to wash them, how to dry them, how often to re-oil, and why a board left to soak is a board you may lose.

Thermo ash and oak: two woods, one routine

The RÅ series, developed with the Danish chef Jesper Vollmer, is made in thermo ash. This is ash that has been heat-treated, a process in which the timber is heated in a controlled, low-oxygen environment. The heat changes the wood's cell structure: it darkens the colour right through to a warm brown, and it makes the wood take up less moisture than untreated ash. Less moisture uptake means less swelling and shrinking, which is why heat-treated timber is valued for its stability.

Oak, the wood of the Menageri Chopping board 40x29 cm Oak, is a dense hardwood with a pronounced open grain and natural tannins. It is hard-wearing and handsome, but it is still untreated wood at heart and responds to water and dryness in the ordinary way.

The useful point for daily life is that the two woods share one care routine. Thermo ash forgives a little more, oak asks for slightly more attention to oil, but neither should be soaked, and both look and behave better with a thin coat of oil from time to time.

Washing by hand, step by step

Every piece in this guide should be washed by hand. The routine takes under a minute and is the single biggest factor in how long a board or utensil lasts.

1. Scrape first. Clear food from the surface with the back of a knife or a bench scraper, so you are washing wood rather than scrubbing residue into the grain.
2. Use warm water and a little mild washing-up liquid. Wet a brush or cloth rather than the board itself, and wash both faces, not just the side you cut on.
3. Rinse quickly. A short pass under the tap is enough. The aim is to remove soap, not to give the wood time to drink.
4. Wipe dry straight away. Take off standing water with a clean tea towel before the board goes anywhere to air.

The RÅ Chopping board 44x25 cm thermo ash is reversible, so it is worth washing both faces every time even if you only used one. For the larger oak board, the same steps apply: wash both faces evenly so that one side does not stay wetter than the other.

For smells such as onion, garlic or fish, a rub with coarse salt and half a lemon before rinsing is a long-standing kitchen remedy. Use it sparingly, as acid and abrasion both dry the surface and bring forward the next oiling.

Why soaking warps a board

Wood is made of long fibres that take up water and swell across their width, while hardly changing along their length. A chopping board left in a sink, or lying flat on a wet worktop, absorbs water unevenly. The wet face swells, the dry face does not, and the board bends away from the wet side. This is called cupping. As it dries, the fibres shrink back, but not always evenly, and repeated cycles can leave a board permanently bowed or open up cracks along the grain.

The end grain, the short edges where the fibres are cut across, acts like a bundle of straws and draws water in fastest. That is where splits usually begin. A board that has soaked overnight may look fine in the morning and only show a crack after a week of drying out.

Thermo ash moves less than untreated wood, but it is not immune. A 2 cm thick board such as the RÅ, at 44 by 25 cm, has a lot of surface area relative to its thickness, which is exactly the shape that cups when one face gets wetter than the other. So the rule is simple: wash, rinse, dry. Never leave wood to stand in water.

Drying flat, or better, on edge

After towelling off, let the board finish drying in open air. Two habits help most.

• Let air reach both faces. A board left flat on a worktop traps moisture underneath and dries unevenly. Stand it on its long edge in a rack, or lay it flat on a wire rack or across two supports so that air circulates above and below.
• Keep it away from direct heat. Do not dry wood on a radiator, near the hob or in strong sun. Fast, one-sided drying causes the same uneven movement as soaking, only in reverse.

Once dry, store boards somewhere with steady air rather than in a closed, damp cupboard.

Utensils: ladle and whisk

The RÅ Ladle thermo ash is made of heat-treated ash, 30 cm long with a Ø7 cm head. Its main risk is being left to stand in a pan of sauce or soup. Lift it out between stirs, rest it on a spoon rest or plate, and wash it as soon as the cooking is done. Dry the inside of the bowl carefully, since water collects there.

The RÅ Whisk thermo ash/gun metallic combines two materials. The handle is thermo ash, and the seven loops are stainless steel with a gun-metal-coloured coating. It measures 29 cm with a Ø6.5 cm head. Wash it by hand, rinse the loops thoroughly, and dry with the head pointing down so that water runs away from the joint where steel meets wood. That joint is the one place where trapped moisture can cause the wood to swell or discolour, so avoid standing the whisk head-up in a jar while it is still wet. Treat the handle to a little oil when you oil your boards, and keep oil off the coated loops.

How often to re-oil, and how

Oil fills the surface fibres so that water and food juices have less room to soak in. It also brings back the depth of colour in thermo ash and the warm tone of oak. There is no fixed calendar, because frequency depends on how much a piece is used and washed. The wood itself tells you when it is time.

• Look for a pale, dry, slightly furry surface. When thermo ash loses its depth of colour or oak turns grey and matt, it is ready.
• Try the water test. Drip a little water on the surface. If it beads, the oil is still working. If it darkens the wood and sinks in, re-oil.
• Expect more frequent oiling at first. A board in daily use generally needs oil more often in its early life; as the surface builds up, the intervals grow longer.

Use a food-safe oil intended for wooden kitchen tools. Avoid cooking oils that can turn rancid in the grain. Start with a clean, completely dry piece. Apply a thin layer with a soft cloth, working along the grain, and give the end grain an extra coat since it absorbs the most. Leave it to soak in for some hours or overnight, then wipe away anything left on the surface. A thin coat, fully absorbed, is better than a thick one that stays sticky.

If knife marks have raised the grain and left the surface rough, a light pass with fine sandpaper before oiling smooths it out. On a reversible board like the RÅ, oil both faces each time so they stay in balance.

Cared for this way, a wooden board or ladle gains character rather than wear: knife marks soften, the colour deepens, and the piece becomes part of the kitchen. For background on the board sizes in the series, see our guide to RÅ chopping boards in thermo ash, and explore boards, grinders and utensils in the Kitchen collection.