Veneer [German version]

Table of contents

General:
Product information
Packaging
Transport
  Container transport
  Cargo securing


Risk factors and loss prevention:
Temperature Odor
Humidity/Moisture Contamination
Ventilation Mechanical influences
Biotic activity Toxicity / Hazards to health
Gases Shrinkage/Shortage
Self-heating / Spontaneous combustion Insect infestation / Diseases




Product information

Product name

German Holz-Furnier
English Veneer
French Placage
Spanish Chapa de madera
Scientific  
CN/HS number * 44 ff.


(* EU Combined Nomenclature/Harmonized System)



Product description

Veneers are thin sheets of lumber (usually 0.6 - 6.0 mm thick) mechanically separated from a slab of lumber or log and used as a decorative covering for furniture. They are made from roundwood. Roundwood is the term used to describe logs cut to specific lengths across the grain. Veneers are a valuable cargo, especially when produced from rare or exotic wood species.

Veneers are classified as follows:

Sliced veneer - flat cut
Sliced veneer - quarter cut
Sliced veneer - false quarter cut
Sliced veneer - eccentric
Sliced veneer - hewn
Peeled veneer, rotary cut veneer
Figured veneer
Root veneer
Sawn veneer


Conversion of roundwood into veneer:

  1. All traces of bark, dirt and metal are removed from the roundwood.

  2. When producing flat cut, quarter cut and false quarter cut sliced veneer, the roundwood is cut into 2 or 4 pieces using a bandsaw, while for eccentric or hewn sliced veneer, rotary cut veneer, figured veneer and root veneer, it remains in a single piece. Sawn veneer may be separated or remain in a single piece.

  3. With the exception of sawn veneer, the sections of trunk are heated for predetermined boiling times depending upon the wood species.

  4. The portions of trunk are then sliced or peeled.

  5. The sliced veneer sheets are dried in roll or belt driers with steam or hot air to a relative lumber moisture content of 6 - 10%, depending upon the species.

  6. Once dried, the bundles of 24, 28 or 32 sheets of sliced veneer are trimmed parallel with a veneer knife, strapped together, measured and numbered. The dimensions of veneers produced from each section of trunk are listed. Rotary cut veneers are cut to size before drying and are palletized without being bundled.


Wood mainly consists of elongate, firmly intertwined, microscopically small cells. These cells consist of a cell wall and a cell lumen, as a result of which wood is a pore-filled material primarily consisting of cellulose, hemicellulose, lignin and water.

The following Figure shows the macroscopic structure of wood. In addition to the bark and phloem layers, the soft sapwood layers and the hard heartwood layers can also be distinguished. The soft, light-colored sapwood consists of living cells and transports water and nutrients, processes which occur in the outermost annual rings. The hard heartwood consists of dead cells and is often of a dark color due to the deposition of heartwood substances, such as tannins and colorants, resins and other lumber constituents, as well as storage materials.

Figure 1

Figure 1


In comparison to sapwood, heartwood has a lower water content, is heavier, harder and more durable. Trees with a large proportion of heartwood are known as heartwood trees, for example mahogany, cedar and oak. Sapwood trees which exhibit no difference in color and water content between the inner and outer wood are, for example, birch, willow and lime.

"Dressed" lumber is lumber from which the sapwood has been removed. Sapwood is highly susceptible to insect attack, while heartwood is less so.


Quality / Duration of storage

Veneers are classified into the following grades:

Faces, outer veneers or fronts are the veneers which are seen as the outer surface on the outside of items of furniture, doors, sheets, panels; i.e. high grade, valuable veneers.
Backs, verso veneers or B sides are veneers visible on the inside of pieces of furniture, the reverse sides of sheets, drawer interiors etc.; i.e. less valuable, lower grade veneers.
Core veneers/plies are veneers which are not visible, e.g. undersides of items of furniture, reverse sides, panels, intermediate layers, plywood etc.


Intended use

Veneer is primarily manufactured for the furniture industry. A distinction is drawn between face veneers and cross-ply veneers, depending upon their intended use. Since face veneers determine the appearance of the product, sliced and rotary cut veneers are used for this purpose. Cross-ply veneers act, for example, as intermediate layers in plywood in order to suppress swelling and shrinkage of the lumber


Figure

(Click on the Figure to enlarge it.)

Veneer

Figure 2



Countries of origin

Veneers are today transported worldwide from and to all continents.


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Packaging

Packaging varies depending on the mode of transport. Short-haul transport operations are carried out with curtainsider trucks or open trucks with tarpaulins covering the load.

20' or 40' standard containers or suitable boxes which are completely lined internally with film so that any water which does penetrate can always run back out of the box on the film are used for shipping or maritime transport.

Open pallets, which must be covered on top with film and boards, are generally used inside the truck or container. The top of covered pallets must be as horizontal as possible so that they can be stacked on top of one another without causing damage to the lower pallet.

Pallets and boxes must be strapped with strong steel strapping every 80 to 100 cm, if possible under pressure. The more tightly are the veneers compressed on the pallets, the lower is their sensitivity to external influences. Excessively weak pallets may break, so simultaneously breaking the veneers.

Pallets must always be loaded horizontally. If necessary, the upper layers must be supported from beneath with squared lumber in such a manner that the pallets may be unloaded again from the top with the forks of the forklift trucks.

Pallets, crates and boxes should be made from dry lumber. If fresh or wet lumber is used, sufficient protective film must be used between the lumber and veneer as very considerable mold growth may occur on the veneer in the vicinity of the wet lumber.

Pallets are generally used because they are substantially cheaper than boxes.


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Transport

Symbols

Symbol, general cargo

General cargo



Means of transport

Ship, truck, railroad


Container transport

Transport in standard containers, subject to compliance with lower limits for water content of goods, packaging and flooring.

Before loading, the containers must be checked for leaks in order to avoid damage due to water penetration.


Cargo handling

Veneer must be protected from moisture (rain, snow etc.) during cargo handling, as there is a consequent risk of waviness or mold and fungus growth.

Forklift truck drivers must approach palletized goods with extreme care. If the forks come into contact with the bundled, unprotected veneers, considerable damage is inevitable.

If the bottom and top are not parallel one to the other, the pallets are very difficult to stack. In such cases, it is essential at least to provide lumber supports to ensure that the pallets can still be unloaded by forklift truck on arrival at the destination. In other words, the forks must still be able to pass beneath the pallet. If this is not possible, veneers may be damaged by forceful unloading unless the pallets are undone, the packages of veneer individually unloaded manually and repalletized. In either case, damage occurs due to tearing and breakage, not to mention the additional unnecessary labor involved in manual unloading.


Stowage factor

2.86 m3/t (veneer, glued, as package) [1]
3.19 m3/t (veneer, packages and boxes) [1]


Stowage space requirements

dry


Segregation

Fiber rope, thin fiber nets (preferred)


Cargo securing

Veneer must be transported in vehicles having a headboard and side walls with sufficient strength and loading capacity. Nonslip material must also be placed under the load and between layers. Gaps in the load are often unavoidable due to the handling methods used and vehicle characteristics (load distribution), so the load must be secured in accordance with anticipated accelerations by direct securing (e.g. tight fit, loop lashing) and/or by frictional securing (e.g. tie-down lashing).


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Risk factors and loss prevention

RF Temperature

Veneer requires particular temperature, humidity/moisture and possibly ventilation conditions (SC VI) (storage climate conditions).

Favorable travel temperature range:    < 25°C [1]


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RF Humidity/Moisture

Veneer requires particular temperature, humidity/moisture and possibly ventilation conditions (SC VI) (storage climate conditions).

Designation Humidity/water content Source
Relative humidity 65 - 70% [1]
Water content 10 - 15% [1]
Maximum equilibrium moisture content 70% [1]


If the palletized veneers exhibit moisture damage from the outside only, a leak has occurred. If the truck or container was checked for leaks before acceptance of the load, it may be assumed that the damage occurred during prior storage.

However, if the veneers are thoroughly wet or exhibit an excessive moisture content, this is an indication of a production or drying defect.

There are three causes for waviness of veneer:

If the veneers are dry and also exhibit no moisture stains or rings, a production error (excessively rapid drying) may have been the cause.
If stains and rings are visible, but the veneer is nevertheless dry and wavy, it is to be suspected that the veneer has become damp during storage and has redried.
If the veneer is still wet and wavy, the damage may have occurred during transport or storage. In the latter case, the truck or container must have been leaky or loading was carried out in rain.


Veneer should not be stowed in a hold with rafted logs in order to avoid moisture damage. On the other hand, however, drying-out (cracks) or warping of the sheets must be avoided.

The lumber "works", i.e. swells as it absorbs moisture and shrinks as it dries (hygroscopicity).

Sorption isotherm

Figure 3


Lumber may be divided into the following water content classes:

Water content Designation
0% Kiln dry lumber
6 - 10% Room dry lumber
10 - 12% Very dry lumber
12 - 15% Air dry lumber
15 - 20% Slightly dry lumber
20 - 25% Green lumber (forest dry)
30 - 33% Fiber saturated lumber
> 33% Water saturated lumber

Fiber saturation means that the cell walls (microsystem) are maximally filled with water, while water saturation means that all lumens (micro- and macrosystem) are maximally filled with water.


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RF Ventilation

Veneer requires particular temperature, humidity/moisture and possibly ventilation conditions (SC VI) (storage climate conditions).

If the product is dry for shipment, ventilation is not normally required.

However, if there is a risk of drying or moisture damage, ventilation should be provided. The following ventilation measure is then recommended:

Recommended ventilation conditions: air exchange rate: 6 changes/hour (airing)


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RF Biotic activity

Veneer displays 3rd order biotic activity.

Respiration processes are essentially suspended, but biochemical and microbial processes continue.


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RF Gases

No risk.


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RF Self-heating / Spontaneous combustion

Fire can only occur due to an outside source, not by spontaneous combustion. If the pallets are well pressed and firmly strapped, there is insufficient air/oxygen between the individual sheets and packages of veneer to allow the veneers to burn properly. At most, they can pyrolyze or slowly smolder away from the outside, and these are very slow processes. The actual damage arises during the subsequent extinguishing operations. The veneers must all be redried and recut, which are very highly labor-intensive operations. The veneers also suffer water marking. After recutting, the veneers are usually too short for high-grade use. They may, however, still be sold as lower grade core veneer in order to minimize losses.


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RF Odor

Active behavior Glued veneers and veneers made from acidic wood may have a slightly unpleasant odor.
Passive behavior Veneers are sensitive to penetrating foreign odors.



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RF Contamination

Active behavior Veneers do not cause contamination.
Passive behavior Veneer must be protected from dirt, fats/oils, colorants and the like. Sand blown on or into the stack on the quayside before loading may be pressed into the surfaces during subsequent tight storage on board, resulting in considerable damage which cannot be removed by remachining.

In the case of woods with a high tannin content, contact with metals may result in oxidative discoloration and staining, e.g. oak veneers in contact with steel strapping or sheet as edge protectors.

Blue discoloration may also be caused by blue stain fungi (blue stain).



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RF Mechanical influences

Veneers are brittle and fragile and, as a result of this mechanical sensitivity, have a tendency to break. Breakage is possible especially with pallets which are shorter than the veneer. A distinction is drawn between longitudinal and transverse breakage:

Longitudinal breakage: if damage has occurred simultaneously to the entire pallet, it is a case of transport damage. Otherwise, longitudinal breakage can only be due to a packaging, or usually processing, error.

Transverse breakage: This may also be a case of transport damage if the pallet is simultaneously broken. Otherwise, transverse breakage may go back as far as the roundwood and have been caused during felling of the tree in the forest.


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RF Toxicity / Hazards to health

No risk.


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RF Shrinkage/Shortage

Depending upon the desirability of the product, either the veneers, including the means of transport, or only part of the consignment is/are taken.


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RF Insect infestation / Diseases

Mold growth may occur if excessively moist veneers are packaged and sweat in the container or truck or in the box on board.

Fungal attack, which results in discoloration, is attributable to deficiencies in the procurement, processing and drying of the roundwood. Fungal growth develops vigorously in the excessively moist lumber enclosed in the film-lined box and closed container.

When determining the cause of the loss, whether due to mold growth or fungal attack, it is essential to ascertain when the moisture got into the product.

The quality of veneer is also degraded by worm infestation. Infestation with living worms is attributable to incorrect treatment of the roundwood. The roundwood has not been chemically treated (e.g. with insecticides), has not been sufficiently cleaned and neither steamed nor boiled, as a result of which the pests have not been killed.

Worm infestation may also have its origins in a preceding cargo. If the hold or container has not been correctly cleaned before loading, any worms present in the preceding cargo (e.g. cereals or worm-infested lumber) may also be transferred into the veneers.


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