The past few years have seen the emphasis on mega yacht topcoats shift from gloss and distinction of Image (DOI) to include more subtle aspects of aesthetics such as orange peel.
Orange peel describes the waviness or structure in a spray applied, dry paint film. The structure is created by the combined effects of a number of factors such as solvent evaporation, solvent blend, film thickness etc. As the solvent evaporates and the drying reactions take place, the paint film becomes increasingly viscous until the point is reached where flow effectively ceases. The structure of the film surface – the orange peel visible to the naked eye can be mathematically described as an overlay or composite of features which reflect a number of different wavelengths, that combine to give the orange peel effect.
Currently, the acceptability of the level of orange peel is mostly judged by eye, but this subjective judgement has led to much argument and discussion due to differences in expectation and acceptability. Using a machine such as a Wave-scan to measure the surface and assess acceptability would appear to be the ideal way to remove subjectivity and substitute objectivity into this difficult area.
Wave-scan was developed for the car industry, specifically to produce measurements, remove objectivity and reduce debate. The principle behind the machine is straightforward. It measures the reflected light from the surface then resolves the different component features by a series of mathematical filters to produce a set of readings. In principle, these readings can be used to establish an optical profile to include in the specification for any painted surface.
The difficulty with this approach is that the link between an acceptable level of orange peel and the Wave-scan numbers that describe that orange peel is not well understood. On the one hand, measuring the surface appearance using an instrument removes the subjectivity from any assessment. However, there is a danger that a customer can be misled into thinking that the numbers agreed in a specification accurately reflect the anticipated surface appearance. In our experience, this is very definitely not the case. We have seen specifications set so wide as to be essentially meaningless. In one case, the range in the specification was so broad that the paint film could vary from being almost optically flat to as rough as a ploughed field. A consequence of this is delayed delivery for the customer and often an expensive repaint for the yard in order to settle the dispute.
Although Wave-scan is becoming more widely used within the yachting world, it is debatable whether the current level of understanding is at the stage where it can be used to set satisfactory specifications. A far better understanding of the data generated by Wave-scan, is required by both the users of the equipment and how it relates to a finished appearance for their customers. At the present time it seems it is a case of buyer beware you may think you have a specification based on Wave-scan that represents fully your requirements, but that is not necessarily the case. So, if a specification is proposed uses Wave-scan data, it is sensible (and economical in the long run) to seek good advice to ensure a meaningful specification is agreed that is achievable and in line with customer expectation of the final coating appearance.
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