Gloss & Appearance

Inconsistent Colour

For consistency, ideally a coating's film thickness ought to be the same no matter where on the part.  Where build-up occurs at the edges of a part, this is called 'Picture Framing', and on flat sheets 'Striping'.

Picture Framing

Higher film build on the edges of the part due to wrap, therefore uneven flow

  • Potential Cause

    Spray gun settings are not optimal

  • Solution

    Reduce voltage to suit part.  Adjust/increase distance.  Adjust powder flow

  • Potential Cause

    Powder Coating has too much flow, particularly if the bottom edges are heavy, or dripping and the upper edges show signs of the powder pulling away.

  • Solution

    May be film thickness dependent; ensure the film build is not too high. Contact us for a sag resistant product.

  • Potential Cause

    Metallic effects: picture framing occurs when metallic particles build up around the edge of a component, which gives the edge a different appearance to the rest of the component it is usually caused by inconsistent application techniques

  • Solution

    If automatic guns are being used, the reciprocators should be set so that they do not ‘dwell’ opposite the edge of the panel at the top and bottom of the stroke .  Additionally, the gap between components and the track should be kept as small as possible.

    If manual application is being used, the spray action should be consistent and very high film thickness should be avoided.

Striping

An inconsistent colour effect, usually in textured effects, metallic products, or products with lower opacity such as whites and yellows.  The colour can be seen to change in regular patterns, or 'stripes'.

  • Potential Cause

    Reciprocator speed is too low,

  • Solution

    The reciprocator speed should be increased slightly.

  • Potential Cause

    Incorrect gun nozzle used

  • Solution

    Check that the gun nozzle slots are correctly orientated, i.e. horizontal to give as wide a spray pattern as possible. 

  • Potential Cause

    Where manual application is being used, the spraying action is inconsistent. 

  • Solution

    The spraying action should be changed.  Carry out tests to practice the best methods of reducing the effect.

  • Potential Cause

    Gun to part distance too close

  • Solution

    In some circumstances the effect can be reduced by increasing gun to workpiece distance.

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