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Under Bound Surfaces

Cause

Flaking is due to the underlying material being under bound Material which in case is old distemper

Solution

Complete removal of all the coating should be removed back to a sound surface.

Patch repair and painting is not advisable.

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MDF (Medium Density Fibreboard Paint Sinkage)

Cause

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.

Remedy

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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 Wet Wood Rot

Cause

A moisture content in wood in the region of 40% + is the point when the timber fibres begin to degrade. The major cause is poor maintenance, allowing moisture to enter the wood when exposed to the elements or for example, internally, where the sealant/putty seal between the glass and window frame has failed and condensation occurs, the water is then absorbed into the wood, affecting the cross rails, cill and styles.

Timber affected by Wet Rot will feel soft and spongy (even through a coat of paint) and look darker than surrounding timber. When dry, the timber will easily crack and crumble into fine particles. It can also be susceptible to shrinkage.

Some types of Wet Rot cause the wood to bleach.  This is common in doors and window frames.

If the paint film is damaged and not treated this can increase the risk of wet rot. If you suspect wet rot and the paint film is not damaged, push a thin bladed knife into the painted timber. The blade should stop after a short distance.  If it goes in up to the handle, it is almost certainly a sign of rot behind the paint coatings.

Remedy

Wet Rot is easier to deal with than Dry Rot, as the cause is restricted to where moisture has entered the wood. Depending on the degree of Wet Rot, it may be necessary to remove and replace a section or the item, e.g. window/door. Where the defect is restricted to one area then it may be possible for a qualified joiner to cut it out and replace with new wood. Alternatively, a special two component wood repair system can be used by following the manufacturer’s instructions. Painting can then be carried out in accordance with the proposed specification.

For further information and specific advice contact: www.repair-care.co.uk   windowcaresystemsang  (Video)

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Wood Rot

Cause

Wood Rot: comes in two forms Dry and Wet. (see wet rot)

Dry Rot. The term implies that the timber is in a dry condition but it would normally have a moisture content reading of approximately 28%.

This along with a damp humid environment can lead to fungal growths forming on the timber.

Once the fungi spores /growths are established even though the moisture content of the wood has dropped and the cause remedied, the spores can still survive if the moisture content in the timber is still around 20%.

The fungi feeds on the wood and extracts the moisture/water which results in the wood structure becoming dry and brittle.

Remedy

The affected areas should be treated as soon as possible as the fungi spores can quickly spread. In domestic situations dry rot can often be found under floorboards at ground level where the air bricks are blocked. Other areas can be unvented cellars and roof spaces.

In these cases the assistance of a specialist wood preserving company should be sought.

For further information and specific advice contact:

https://www.rentokil.co.uk or search for local contractors

For wood repair systems: www.repair-care.co.uk  windowcaresystemsang

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Cause

Yellowing  and discolouration of an oil based paint excluded from normal sunlight.

White and pastel colours are mostly affected.

A newly applied coating to oak timber styles showing tannic acid bleed .

Bleeding from a wood knot which was not sealed with shellac knotting

Bleed from the underlying coating being bitumen based and activated by the solvents in the finishing material.

Remedy

No solution for the those areas excluded from daylight other than using waterbased paints.

Where hardwood requires painting a leafing/flake base aluminium primer should be used.

Also see: Discolouration

The post Yellowing appeared first on Paint Check Plus.

Crows footing

Cause

Problems of this type occur when coatings, particularly water based paints are applied onto a surface which has a higher sheen level resulting in the adhesion quality of the newly applied paint being low, for example a matt emulsion being applied over a vinyl silk or an oil based coating.

It can also occur when water based paints are applied to new plaster without being thinned as a sealer coat.  This can result in the VOC’s (Volatile Organic Compound) being quickly absorbed into the surface resulting in poor adhesion of the coating.  Consequently, as the newly applied paint hardens the tensile strength of the newly applied paint film begins to shrink and cracks in the paint film appear.

Solution

After rubbing down and face filling with a fine plaster filler, applying a paint coating of a higher sheen level will in most cases overcome the problem.

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Crinkling

Cause

Softening of a previously applied coating caused by applying a subsequent coat before the underlying paint film is totally dry. Problems of this nature can also be as a result of applying paints such as chlorinated rubber which contain strong solvents over alkyd based paint finishes.

This type of problem can also occur when water based coatings are applied over an oil based sealer such as Alkali Resisting Primer or Stabilising Solutions for use onto a powdery substrate. And where the sealer coat has remained glossy and not flatted down before applying the top water based coats..

Solution

Occasionally it may be possible to remove the ridges. In severe cases complete removal may be necessary before re – painting can take place.

See Rivelling

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Ropiness

Cause

Ropiness of a paint coating caused by the material being high in viscosity (thick), with very little flow. This also occurs when paints of normal viscosity are applied without care.

Solution

The ‘ropy’ finish must be thoroughly dry and flatted down with carborundum paper (wet or dry) used wet, with water as a lubricant. If repainting with the same product adjust with appropriate thinning agent to the correct viscosity before re–painting.

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Cratering

Cause

Problems of this nature can be caused by rain falling onto the semi dried coating or  aeration/frothing of the paint during application usually by roller and not flowing out properly. Also referred to as pin holes

Solution

Once the coating is completely through dry, flatting down should take place using carborundum (wet or dry) abrasive paper preferably wet – using water/soap  or white spirit as a lubricant. Recoat with chosen paint finish.

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