MDF Sinkage of priming coat

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Proimer sinkage into the raw cut edges

MDF (Medium Density Fibreboard Paint Sinkage)


MDF is manufactured by breaking down unwanted wood into fine fibres which are in turn mixed with resin and paraffin wax, followed by compressing the mixture under high pressure into panels.

MDF is a fine finishing board used extensively in the building industry and primarily for trim work such as door lining, architraves, skirting boards, window boards and moulded doors.

While the finished surface of the boards are smooth, the edges and any areas where trimming has been carried out, the finished MDF is coarse with an open surface.

Applying water-based primers can lead to several problems:

  1. The surface of the MDF may have residual wax present, which would result in poor adhesion onto the surface
  2. Depending on the MDF grade, the water content in the water-based primers could be absorbed into the surface and lift the wood fibres causing a rough surface
  3. Water-based materials will penetrate into the edges and bare moulded areas, and will not provide a sealed surface for finishing coats.


Prime all bare areas with an oil based primer. This can then be over-coated with either oil based undercoats and finishing coats or acrylic water based finishes.

For construction, other grades are available:  Fire-resistant grade is colour coded Red and Moisture- resistant grade is colour coded Green.

Health and Safety

As the MDF fibres are very fine, wearing a face-mask during sanding or cutting is advisable.



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