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    TIMBER SUBSTRATES
    TROUBLESHOOTING PAINT PROBLEMS RELATED
    TO
    TIMBER SUBSTRATES
    JUNE 2010

  1. 1. BLEEDING

    Description
    Staining and discolouration of the topcoat due to the migration of volatile components from the underlying coat. In this particular example it is creosote.

    Possible diagnosis
    • The coloured ingredients in the previous coat are dissolved by the solvents of the subsequent coat and migrate to the top leading to staining and discoloration.
    • Over coating coal/tar containing paints, bitumen, asphalt or creosote with white or coloured topcoat, will result in the first coat bleeding through the subsequent coating.

    Remedy
    • If possible remove all of the coatings to bare substrate. Best results are generally achievable in the case of creosote if it has weathered well to a sooty grey colour.
    • Removing oil, wax or tar-like substances from porous substrates is very difficult to achieve and it might be advisable to continue with the original coating.
  2. 2. FISH EYES OR SURFACE BREAKS

    Description
    Retraction of a new coating from the surface leaving voids. In this example, the previous coat consist of a solvent-based wax wood preservative, over coated with a white water-based emulsion coating.

    Possible diagnosis
    • Oil, grease, wax, moisture and or silicon contamination or coatings on the surface are not permitting the surface to be wetted by the subsequent coating.
    • Very smooth or polished surfaces which result in bad adhesion.

    Remedy
    • Remove oil, grease, wax, moisture and/or silicon contamination. 
    • Apply NEO Sieggelack, NEO Wood Coating or other NEO Paints’ varnish products as per instructions.
  3. 3. FLAKING

    Description
    Paint lifting and flaking from wood in exterior applications. Signs of grey, weathered wood at exposed areas.

    Possible diagnosis
    • Natural weathering and a lack of periodic maintenance.
    • Moisture ingress from untreated or sealed timber ends/edges.
    • The lack of a specialized wood primer.
    • Painting over decayed wood without proper surface preparation.
    • Using improper coating system without the necessary flexibility required for expanding and contracting wood substrates.
    • Fresh timber having initial high moisture content shrinks.

    Remedy
    • Remove coating and grey weathered wood surface. 
    • Recoat with specialised NEO Wood- coating as per instructions.
    • Make sure to seal exposed edges/ends.
  4. 4. FLAKING OF CLEAR VARNISH

    Description
    Paint lifting and flaking from interior or exterior wood. Signs of grey, weathered wood at exposed areas.

    Possible diagnosis
    • Natural weathering and a lack of periodic maintenance.
    • Insufficient coats of varnish.
    • Moisture ingress from untreated or sealed timber ends/edges.
    • Using improper coating system without the necessary flexibility required for expanding and contracting wood substrates.

    Remedy
    • Remove coating and grey weathered wood surface by means of sanding.
    • Wash off any varnish residue with white spirits. 
    • Recoat with NEO Clear Lacquer, NEO Plastic Varnish, NEO Woodcoating or other NEO varnish products as per instructions.
  5. 5. KNOTS AND RESIN

    Description
    Hard, cross-grained disfigurements in timber which are formed where shoots on trees are developed into branches.
    Golden sticky resin exuding at knot.

    Possible diagnosis
    • Normal characteristic of wood.

    Remedy
    • Knots exuding resin should be drilled out whenever possible and the hole plugged.
    • Alternatively an attempt can be made to remove any free resin. Wipe down the surface with white spirit followed by knotting compound.
    • Normal knots can be treated with knotting compound at least 1cm beyond the area to be treated, feathering off the edges. Apply knotting compound thinly as to avoid thick edges.
  6. 6. WOODBURN

    Description
    Dark golden discoloration of the wood substrate under clear varnish in UV exposed conditions.

    Possible diagnosis
    • The use of an interior varnish that does not contain UV absorbers in an UV environment.

    Remedy
    • Remove coating and top layer of wood surface. 
    • Recoat with NEO Woodcoating UV resistant varnish.