Determining the condition of the existing finish It is important to determine the condition of the finish. This initially can be a visual one, looking for any obvious signs of colour fade, surface chalking or poor adhesion. NOTE: A visual inspection does not always give you an idea on surface adhesion and we would always recommend a St Andrews Cross-Cut Test to fully evaluate the condition.
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The
St Andrews cross test consists of two lines cut through the coating
(using a sharp decorators knife ie 'Stanley' type or similar) to the
substrate beneath. The adhesion can be tested by inserting the point
of the knife into the 'V' intersection and firmly dragging or flicking
the knife forward or upwards. This is a practical on site adhesion
check that will give an indication of the factory coating adhesion,
and whether it will support a redecoration.
The
coating shall be deemed sound to overpaint if no or very little of
the coating is removed by the above test.
If
the coating can be quite readily chased up the surface with the knife,
it shall be deemed unsound, and removal of the coating is required
prior to treatment
