Repairing a finish

First recognise the finish

Every repair starts with the question of what is on the wood. The wrong product can do more harm than the scratch itself: oil does not adhere to lacquer, and methylated spirit dissolves shellac. Anyone who made the piece or knows the maker can ask. Otherwise three simple tests help, each on a hidden spot:

• Drop of water: if it beads, a lacquer, wax or hard-wax oil still protects the wood. If it soaks in and darkens the wood, the finish is worn or missing at that spot.
• Methylated spirit: a dab of spirit makes shellac soft and tacky after a short time. Oil, hard-wax oil and most lacquers stay unchanged.
• Raking light: a lacquer film shines evenly across joints and pores. Oiled surfaces leave the pores open and reflect differently depending on the species.

Before any repair the surface is cleaned. Much of what looks like damage is dirt or grease from hands and comes off with a slightly damp cloth.

Touching up hard-wax oil

Hard-wax oil is the easiest finish to repair, because it forms no closed film. New oil bonds with the old, and the edges of a repair blend in. Three levels, depending on the damage:

1. Dull or lightly marked: clean, let dry, apply a very thin coat of the same hard-wax oil with a cloth or pad, and wipe off the excess as the manufacturer states. Too much oil stays tacky and shines in patches.
2. Scratch in the finish or water mark at the surface: sand the spot lightly with a fine abrasive pad or fine paper, a little beyond the damage, remove the dust and re-oil thinly. Once dry, add a second thin coat if the spot still looks more matt than its surroundings.
3. Whole face worn: sand the whole side finely until scratches and marks are gone, and build it up again as the first time. At Reihax that means two thin coats of hard-wax oil in a satin sheen, with a light sanding with a fine abrasive pad in between. That is how a whole side of a finished piece has already been renewed in the Reihax workshop.

It is important to use the same product at the same sheen. A different oil or a different sheen stays visible as a patch, even if the repair is otherwise successful. If the product is unknown, test on a hidden spot first.

Water marks and rings

There are two kinds of water mark, and they are treated quite differently:

• Light, milky ring: moisture is trapped in the finish itself, typically in wax, lacquer and shellac. Careful polishing or gentle warmth, such as a hair dryer on a low setting, often helps the moisture escape. On hard-wax oil the spot is treated like a scratch: sand lightly and re-oil.
• Dark mark: the water has soaked into the wood. On tannin-rich woods such as oak, water together with iron, for example from a glass on a metal coaster, even turns black. Such marks sit in the wood and can only be removed by sanding or with wood bleach.

On veneer the dark mark is the harder case. Sanding only goes as far as the thickness of the veneer allows, and wood bleach also lightens the surrounding wood. Sometimes it is better to leave the mark or to replace the affected field (fixing mistakes).

Touching up lacquer

A lacquer forms a film, and a scratch in it is a notch in the film. It can rarely be closed invisibly on the spot, because the edges of the repair stay visible in the sheen. Fine scratches sometimes disappear with polishing compound. Otherwise the whole affected face is sanded lightly up to an edge or a joint, dusted and lacquered again, with the same lacquer and sheen. On veneer only the lacquer is sanded, not the wood, with hardly any pressure at the edges (lacquering).

Touching up shellac

Shellac is the counterpart to lacquer: new shellac redissolves the old and bonds with it. Scratches and worn spots can therefore be repaired almost seamlessly by applying new shellac thinly and letting it flow out. In return shellac is sensitive: water, alcohol and heat quickly leave light rings, which can likewise be polished out or reworked.

The limit on veneer

Solid wood forgives almost any repair, because there is more wood under the damaged layer. Veneer is only a fraction of a millimetre thick, and after the first sanding there is less of it left. Every repair that sands costs thickness, and at edges and corners the limit is reached fastest.

Photo: Reihax

• Sand only the finish, not the wood, as long as the damage sits in the finish.
• Work with a fine abrasive pad or fine paper, never with a coarse grit.
• Hardly any pressure at edges; do the edge itself last and by hand.
• If the veneer itself is damaged or sanded through, repair the wood first, then the finish.

Photo: Reihax

Looking after Reihax pieces

Reihax pieces, the pen holders as well as the wall art, need no retreatment in normal use. Dusting with a soft, dry cloth is enough; re-oiling is not needed. Cleaning products, wet cloths and furniture polishes are unnecessary and can harm the surface. How wooden objects are otherwise cared for and placed is described under caring for handmade wooden objects and UV light and ageing.

Checklist before a repair

• Finish identified: asked the maker or tested on a hidden spot
• Surface cleaned; checked that the damage is not just dirt
• Damage placed: in the finish or in the wood
• The same product at the same sheen to hand
• Fine abrasive, no coarse grit, hardly any pressure at edges
• Applied thinly, excess wiped off, drying time kept
• Result checked under raking light next to the undamaged surface