All posts by Paul Edwards

Accelerated Weathering Laboratory Ltd celebrates its 10th year of Materials Testing

As AWL Ltd celebrates its 10th year in business with year on year steady growth in terms of turnover and profits, I would like to take this opportunity to thank all of our clients, both UK and overseas for their continuous business and support.

I would also like to thank our small team of dedicated staff who have provided the efforts required to maintain this growth by response to demand in a timely and efficient manor in accordance with our ISO 17025 / ISO 9001 quality systems and policies.

I would also like to thank our key suppliers for their support over the past 10 years.

Paul Edwards, Technical Director, Accelerated Weathering Laboratory (AWL) Ltd.



Help! What’s the difference between LRV, LAB and ΔE values ???

We are often asked to provide LRVs and / or CIE colour-space values with Delta E (ΔE or dE) after accelerated weathering tests to quantify photo stability performance. However, these three sets of numbers are often misunderstood or not understood at all!

We would like to shine some light on the matter (pun intended) and provide a very basic understanding of their differences and how best they can be used.

LAB CIE colour-space readings and Delta E (ΔE)

The CIE LAB colour-space model is a complex mapping system that uses tristimulus (a combination of 3 colour values close to red, green and blue) which are plotted as a 3D space. When these values are combined they can reproduce by providing coordinates for, any colour the human eye can perceive.

Deltas E is defined as the difference or change between two colours within LAB colour space and are used in our laboratory for quantifying photo stability performance after accelerated weathering testing. LABs are best used as raw data for calculating Delta E values to provide a measure of colour shift in any direction after UV exposures and are particularly useful for pigment manufactures when a primary colour may degrade from a secondary colour changing it completely.

For example, if a secondary colour like green is manufactured from a mix of primary colour pigments blue and yellow, the LAB coordinates will show whether it is the blue or yellow pigment (or a combination of both) ‘burning out’. This will identify ‘weak pigments’ should there be even a subtle colour shift.

Please also be aware that although Delta E values provide us with a number to quantify colour shift, the perception of colour change for the same dE value will be strong in a grey scale, but weaker in some colours.

Light Reflectance Values or LRVs

Light Reflectance Values (LRVs) describe the quantity of visible light reflected by a surface in all directions when illuminated by a light source. The LRV is similar to (not the same as) the CIE colour space direction ‘L’ from black to white.

LRV measurements are used to establish how much light a particular colour reflects, and conversely how much light is absorbed. LRVs are reported as percentage values from 0% to 100%. Zero assumed to be absolute black and 100% assumed perfectly reflective white. The instrument is calibrated at 0 and 100% using black and white calibration tiles.

LRVs are best used to measure fade after accelerated weathering tests but are more commonly used to provide interior designers and architects a perception of how much colour will be reflected back into a room when the lights are turned on. You will often see LRVs stated on colour swatches in your local DIY store which is an establishment I avoid like the plaque!

Hope this helps.

Still confused?

Yes I agree, we should both get out more!


Paddy Hopkirk visits AWL Ltd to discuss number plate testing

It was a pleasure to receive a visit from the icon Paddy Hopkirk (1964 Monte Carlo rally winner) last week to discuss number plate testing, legislation and his involvement with the charity SKIDZ.

SKIDZ provide industry-recognised training and education in motor vehicle maintenance to young people of all abilities. They have also launched a business to provide motor manufacturers, dealerships and fleet firms with everything they need to create their own number plates on demand.

The project is being championed by SKIDZ Patron Paddy Hopkirk, the legendary rally driver, is in its infancy but SKIDZ believes it has massive potential with profits from the enterprise going to support SKIDZ students. Check out their website at

AWL Ltd were pleased to be approached by Paddy with the prospect of providing consultation and validation for their suppliers in terms of performance against the current British Standard for number plates BS AU 145d.


Super-hydrophobic coatings and there impact on anti-friction and corrosion performance.

The techno sounding term ‘hydrophobic nano-coatings’ describes the application of thin films onto various substrates normally for protection against the elements. These thin films may be simple in nature and applied manually (polishing and waxing of automotive paint finishes as an example).

These coatings are usually without structure (flat) acting as a barrier coating to repel water away from the substrate using the relative surface tension properties of the coating verses the water droplets while also providing an aesthetically pleasing shine. There are many other more complex methods of applying thin films for protection of various metallic and polymeric substrates such as ion exchange and spatter techniques.

Our accelerated weathering and environmental testing laboratories have helped provide numerous thin film manufacturers with a means of measuring weathering performance by exposure to simulated sunlight with controlled variations in humidity with or without water spray to provide thermal shock and to mimic rain.

This test method is called xenon arc weathering and is the best laboratory replication of full sunlight spectrum between 290 and 800nm. Geographical location can be taken into account by adjustment of irradiance, temperature and relative humidity levels.

Super-hydrophobic coatings are even better at water repulsion as well as providing excellent anti-friction / non-stick properties. These coatings must have a topographical structure to work well and there impact on corrosion protection is vast due to there ability to repel water and keep oxygen from the air away from the substrate therefore stifling the corrosion reaction equation in metallic materials.

There are many examples in nature of super-hydrophobic surfaces and probably the best known one can be described with the saying ‘water off a ducks back’. The complex ridged structure of feathers help to provide super-hydrophobic properties causing the water to be attracted to itself so it will ‘ball up’ and roll away without a trace.

Take a look at this video (see link below) and let your imagination run wild with the numerous applications in all sectors (industrial, aerospace, automotive, electronic, textile, bio-medical etc…) where super-hydrophobic coatings can protect and enhance the performance of low cost substrates.


Number plate material importers beware!

UK importers of materials to be used for manufacturing number plates shall need to ensure the product can satisfy the requirements of the new number plate quality standard BS AU 145e.

When a full suite of testing cannot be justified due to cost or time restraints then material quality may be initially qualified by satisfactory performance after thermal resistance against distortion (clause 12), resistance to bending (clause 10) and resistance to solvents and abrasion (clauses 11 & 14).

The most expensive and time consuming test is xenon arc weathering (clause 16) which exposes fully manufactured product to UV exposure and moisture in accordance with the standard for around 2200 hours (13 weeks) in order to provide 4500MJ/m2 radiant energy exposure.

Initial qualification will NOT be sufficient to allow use of the BS mark, but may provide the importer with greater confidence regarding the required quality of these materials for number plate end usage. The additional clauses required for full validation can be added later when greater confidence is confirmed.

AWL are still concerned that acceptable equipment required for measuring retro-reflection in accordance with the standard remains unclear. We are currently in discussions with BSI and NPL concerning this but progress is moving at glacial pace.

If there are any suppliers of laboratory equipment that may be able to help us with retro reflection measurements, then please contact us.

AWL are pleased to offer a cost-down opportunity for our clients that contract us to carry out the full suite of testing so they can use the BS mark. Visit our number plate testing page and/or contact us for additional information.


Taber Abrasion: ASTM D4060 Video

Taber abrasion in accordance with ASTM D4060 remains popular at our accelerated weathering and environmental testing laboratory with our coatings clients, particularly before and after UV weathering in accordance with ISO 4892-2 ISO 4892-3, ISO 11341 and ISO 20340. There is a nice little movie on YouTube that shows how this standard can be used for comparing abrasion performance under the same conditions with other coatings perhaps from the competition. Click on the video link below.

Should your company be in the coatings sector and you produce, or provide a service for the application of hard-wearing coatings on softer substrates, and you want to shout about it, then we can help using our Taber Abrasion capabilities to provide relative performance data. Contact us to discuss your requirements.

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