Storing veneer

Why veneer is sensitive to storage

Wood is hygroscopic: it takes moisture from the air and gives it back, and it swells and shrinks as it does. A solid board needs weeks for that. A veneer of 0.6 mm has an enormous surface in relation to its volume and so reacts within hours to days. Whatever the air in the room does, the veneer does too.

Poor storage shows in five ways: the sheet cockles, splits at the ends, turns brittle, gets water or mould stains, or its surface changes colour in the light. All five can be spotted when checking a sheet, but only cockling can still be fixed reasonably well afterwards.

Flat and weighted

Veneer lies flat. The base is a level board, of MDF or multi-ply for instance, a little larger than the sheets on every side; if a sheet hangs over the edge, the end droops and keeps that bend. On top goes a second board and on that a weight spread over the whole area: several medium weights rather than one heavy one in the middle that leaves the edges of the stack free.

• Order of the flitch: sheets from the same flitch stay in the order they came off the log. Only then can you later lay book-matched or mirrored pictures whose figure matches (types of veneer and cuts).
• Not rolled, not on edge: rolled veneer keeps its curve, and sheets leaning on edge bend under their own weight.
• Long sheets: shelves have to be as deep as the sheets are long. If that is not possible, it is better to cut long sheets into handy lengths than to let them hang over the edge.

If a sheet has cockled after all, it can usually be saved: dampen it lightly, lay it between clean sheets of paper and boards and let it dry slowly under weight, changing the paper a few times until the sheet is dry.

Room climate and humidity

A good store has a steady temperature and a humidity of about 40 to 60 per cent. More important than the exact figure is that it stays steady. At around 20 °C and 50 per cent humidity, wood settles at about 9 per cent moisture content, a typical value for heated rooms. A simple hygrometer in the store shows how much the humidity swings over the year.

• Too dry, right by a radiator or in very warm rooms in winter: the veneer turns brittle, splits at the ends and breaks at sharp angles when cut.
• Too damp, in a cellar, a garage or against a cold outside wall: mould stains appear and the veneer swells.
• Swinging, in an unheated workshop with warm days and cold nights: condensation can form in the stack. In such rooms a closed cupboard or storage box keeps the climate calmer than an open shelf.

Covering the stack makes sense; sealing it airtight in plastic only does if the veneer is already dry. If it is still too damp, the moisture is trapped inside and it can go mouldy. Card, brown paper or a cover board protect from light and dust without sealing the stack.

Acclimatising new sheets

New veneer carries the climate of the store it came from. Before it is worked, it needs time to adjust to your own room: a few days to about two weeks, flat and lightly weighted, in the room where it will be cut and pressed. The substrate belongs in the same room, because veneer and substrate should have the same moisture content when glued. What happens otherwise is described in gluing and pressing.

Veneer from job lots, estates or workshops closing down needs more time, because nobody can say how it was kept. The Reihax mahogany comes from such a closure: where and for how long it was stored there is not known. With material like that, acclimatising is part of checking it before any piece of it goes into a work.

Protection from light

Light changes the colour of wood, and not the same way for every species: some darken, others bleach or yellow. In a stack, that only affects the top sheet and only its upper face. The difference often shows only when that sheet lies next to one from the middle of the stack, or when the changed layer is partly sanded away.

So veneer is stored covered and out of direct sun, not even for a few weeks on the bench by the window. How light affects finished pieces, and why contrasts slowly shift there, is covered in caring for handmade wooden objects.

Sorting offcuts

In intarsia, offcuts are not waste. Many pieces are smaller than the palm of a hand, and a strip left over from cutting is often enough for a whole pattern. To keep offcuts usable, they are stored just as flat as whole sheets and sorted so that you can find them again.

• By species and thickness: offcuts of different thickness do not belong in the same place, or a thinner piece ends up next to a thicker one and leaves a step.
• By size: flat boxes or folders for large, medium and small pieces save rummaging, which breaks thin pieces.
• Together what belongs together: offcuts from the same sheet stay together, so that colour and figure match later.
• Mark the grain: on larger offcuts, a pencil arrow at the edge shows how the grain runs, even when the figure is faint (grain direction).
• Throw out: pieces that are brittle, stained or smaller than the smallest planned piece go. A full box of useless offcuts is worse than a half-empty one.

Labelling

Many veneers look more alike raw than after finishing, and you cannot see the thickness at all. So every stack and every box of offcuts gets a label:

• Species: the trade name and, if known, the botanical species.
• Thickness: measured yourself, not just copied from the delivery note.
• Source: the supplier, the flitch number, or simply "job lot".
• Date: when the veneer arrived, so you know how long it has been acclimatising.

An honest label is worth more than a complete one. For the Reihax mahogany that would read: mahogany, workshop closure, species unknown. A label that claims more than you know makes it hard to explain a difference in colour later. Write on the sheets themselves with a soft pencil at the edge, never with a felt pen, which soaks into the pores.

Checklist for the veneer store

• A level base board larger than the sheets, nothing hanging over the edge
• Cover board and weight spread over the whole area
• Sheets from one flitch in their order
• No direct sun, no radiator, no cold outside wall
• Humidity steady at about 40 to 60 per cent, checked with a hygrometer
• New sheets and substrates acclimatised in the workshop for a few days to two weeks
• Offcuts sorted by species, thickness and size
• Every stack labelled: species, thickness, source, date