12th March

Delta E – and why it matters in professional powder coating

For absolute accuracy we need to turn to a measurement called Delta E (or dE). Delta E is a numerical way of expressing the difference between two colours. Using both digitally and visual checking, under controlled lighting, ensures that what the data says and what the human eye sees are aligned.

Colour measurement instruments compare a reference colour with a new sample and calculate how far apart those colours are in a defined colour space. The smaller the Delta E value, the closer the match. Our internal standard is a colour tolerance of Delta E below 1.0, which is the smallest colour difference the human eye can see, although this can differ for different colours. Delta E<1.2 is widely recognised within the coatings industry as a level where differences are extremely difficult to perceive under normal viewing conditions.

Colour matching is one of the most important parts of what we do at Powdertech and there are many circumstances when it is critical.

  • Batch to batch consistency of the powder. Incoming powder batches are verified against approved standards, and finished coated samples are measured and recorded. This allows us to detect even very small shifts before they become visible on site.
  • Maintaining an homogenous colour within a build project.
  • Matching a shade applied to other parts of the building – maybe in wet paint, or another material.
  • Matching a legacy shade.
  • Matching a livery colour.

Making sure your whites are all white

For the £4.2million renovation of Hilton Garden Hotel at Heathrow, were asked to coat long aluminium fins, manufactured by Spanwall, rising from the ground to the 14th storey of the building. These were constructed in sections and were to be coated in a white gloss finish.

It was imperative that every fin was consistent in colour to give a homogenous appearance, both between the fins which would run along the length of the installation and within each sectioned fin.  Even the slightest difference in shade can be detected by the naked eye, and this is especially true with white.

To ensure that the white sections all matched one another we used Delta E measurements. The process started by capturing a measurement for the white shade chosen by our client,  using calibrated colour measurement equipment called a colorimeter. This was done under controlled lighting conditions to ensure that the reference data is consistent and repeatable.

Then we produced some trial panels and measured them against the target colour using both the colorimeter and visual assessment.

Visual assessment  remains essential as real-world conditions – lighting, surface texture and gloss level – can all influence how a colour is perceived once installed.

In addition to the powders themselves there are other factors that can affect how the colour behaves. Environmental control, consistent application techniques and accurate curing profiles are also vital. Changes in film build, oven temperature or substrate preparation can subtly affect colour appearance, even when the same powder is used. With over 40 years’ experience in powder coating, we are well practised at dealing with these factors.

Once we, and the customer, were happy with the trial panels, we went into full production. Again, we took Delta E readings for  every section of every fin. A time-consuming process but, as professional architectural coaters, this was the best way to ensure that all the white panels were the same shade of white.

Kings Cross Blues

On other occasions we are asked to find a colour that will match an existing or previously used shade. This can become very important if customers want to reproduce a colour, sometimes from a different material.

Our work on the Chapter Living project at Kings Cross with Metalline is a good example.

Previously the building had made a colourful statement with windows in two shades of laminated blue glass. This needed to be replaced by powder coated panels, and the designers were keen to retain the shiny blue shades with a high gloss polyester powder coating. Pieces of the blue glass were sent to us and we directed one of our powder manufacturers to make two unique shades of blue to match the old glass in both colour and gloss. We used the Delta E measurement to ensure a close match, and consistency between batches.

Matching a powder coating to a paint

Sometimes we need to match a shade from company livery or within a legacy project where original specifications may be many years old, or as is often the case, unknown.

 

For a solar shading on a warehouse installation in we were asked to match a particular shade of cyan, already used as wet paint, on a band around the exterior of the building. Swatches and samples were sent to and fro between Powdertech and the customer until the cyan shade was perfected and agreed upon.

Whether we are matching new components to an existing installation, reproducing a colour from company livery, or supporting a legacy project where original specifications may be many years old, consistency is essential. Even small differences can stand out once parts are installed side-by-side on site – and once a project is complete, those differences cannot be hidden.

With thorough colour matching techniques, customers can be confident that:-

  • new components will integrate seamlessly with existing structures
  • branded colours remain consistent across multiple batches and future projects
  • replacement or extension works will not visually “stand out” from the original installation

This level of control means fewer risks, fewer delays and greater confidence in the final result.

For our team at Powdertech Corby, accurate colour matching is not simply a technical process; it is part of the service we provide to ensure that your project meets your design vision, most especially in the final component – the powder coating.

Get in touch to discuss your project and any colour matching needs you may have.