Droplet size for spray coating applications

Droplet size has several implications for spray coating.  Finely atomised sprays will have a bigger surface area to volume ratio than sprays comprising of larger droplets.  This means that they will have more overall contact with the target and so will adhere more quickly.  This is particularly important when it comes to drum and fluid bed coating systems because contact is randomised. 

Larger droplets also tend to bounce or shatter on impact rather than stick to a surface.  So, again, will not tend to adhere so well.  Also when they do form a layer the layer will tend to be less even and thicker, meaning any required evaporation may take longer and result in an uneven coating.  The prolonged period of having a wet product increases the chance of product sticking together in fluid bed/pan coating systems or of having partly wet product on conveyor systems.

Coating engineering considerations

Coating nozzles


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