Wood

Account for natural material differences when planning specimens

Wood is a naturally grown material. Colour, structure and moisture content can vary even within a single species. These differences are considered when selecting and assigning specimens so that they interfere as little as possible with the evaluation of different treatments.

Documented initial conditions and suitable replicate specimens are useful for comparative experiments. Sanding condition, application quantity and drying of a surface treatment are also recorded. This makes it possible to establish subsequently which combination of wood and treatment was tested.

Important specimen information:

• Wood species and origin or specimen assignment
• Initial colour, grain and visible material characteristics
• Wood moisture content and conditioning state
• Surface preparation and sanding condition
• Type, application and drying of the surface treatment

Tailor the exposure profile to indoor or outdoor applications

The radiation reaching a wood surface in its intended application also depends on glazing, coatings and other intervening layers. The test concept therefore defines the relevant spectral conditions and which side of the specimen is irradiated.

Alongside light exposure, temperature and, where applicable, humidity or wetting phases are planned. If the interaction of several environmental influences is to be investigated, these must be specifically incorporated into the test programme. Exposure conditions are documented throughout the experiment.

Important exposure parameters:

• Radiation spectrum and application-specific filtering
• Irradiance and spatial distribution
• Exposure duration and radiant exposure
• Surface and ambient temperatures
• Humidity, wetting and drying phases, where applicable

Record colour development and surface condition together

Evaluation begins with a documented initial examination. Repeated photographs and suitable measurements can show how the surface develops over several exposure stages. Measurement locations are identified as clearly as possible, since the natural wood structure can produce local differences.

Depending on the test objective, the condition of a coating or other surface characteristics is investigated alongside colour. A colour change alone is not sufficient evidence of a change in load-bearing capacity or the overall service life of the component.

Possible evaluation parameters:

• Colour change at specified measurement positions
• Gloss and appearance of treated surfaces
• Cracking and changes in surface structure
• Condition and adhesion behaviour of existing coatings
• Comparison of different treatments after identical exposure

Adapt the system to specimen formats and workflows

Wood specimens can have different dimensions, thicknesses and surface constructions. The irradiation system is therefore tailored to the intended formats and the required comparison area. Specimens must be positioned in a defined way and remain accessible for intermediate evaluations.

BF Engineering plans irradiation equipment to suit the test objective and existing environment. The design considers operation, temperature monitoring and maintenance, as well as interfaces with supplementary climatic functions where applicable.

Relevant integration considerations:

• Specimen dimensions, material thicknesses and number of variants
• Defined mounting and repeatable positioning
• Access for photographic documentation and intermediate measurements
• Monitoring of irradiation and temperature
• Cleaning, maintenance and regular verification measurements