Efflorescence
Cause
Efflorescence can originate from any cementitious building products such as brick, concrete blocks, sand: cement rendering and plaster. As moisture or moisture vapour passes through the materials to the surface it will bring any soluble salt deposits within the substrate to the surface. Initially the deposits appear fluffy and can be brushed off. If not removed this will crystalize, build up and damage the surface finish. The salts can remain dormant for many years and efflorescence can appear if the building substrate is affected by water ingress due to water leaks, flooding or a faulty damp proof lining.
Remedy
Decorating should be left until salts cease to appear by constant dry brushing. If painting is necessary then it is best to apply water based coatings of a high pigment content which allow moisture vapour to pass through the paint film more readily than others, allowing further salts to come to the surface without causing any major problems.
Some suppliers recommend treating the area with an alkali resisting primer sealer and while this will reduce any moisture vapour coming to the surface it is possible that any underlying salts could re-appear from the unsealed surrounding areas.
Yellowing
Yellowing
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
Frost Damage
Frost damaged paint
Although water based paints will withstand low temperatures they should always be stored above 5 degrees centigrade.
The illustration shows the result of paint being subjected to extreme low temperatures and has frozen, rendering the product unusable.
Crows footing
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.
Crinkling
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
Ropiness
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.
Cratering
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.
Pattern Staining
Cause
This colour variation is highlighted where there is a difference in thermal conductivity i.e. the joists and the voids between. Or on internal walls of a timber frame construction highlighting the timber or steel upright studs.
Pattern staining has also occurred where cold water pipes have been chased into the wall before plastering.
Remedy
A paint coating can only improve the aesthetic appearance. To solve the problem the voids between the joists need to be filled with glass fibre or some other type of insulating material .
The illustration showing the pipework can only be rectified by re directing of lagging the pipe.
Cheesiness
Cheesiness
Cause
A term relating to a freshly applied coating which, when dry, is mechanically weak. This can be as a result of the coating being applied too thickly, incorrect solvent used or wax / grease on the surface which has not been removed before painting. Attention should always be given when painting doors architraves, particularly the lock side, as body fats can be deposited on the surface.
Solution
The coating should be removed and the surface thoroughly washed and flatted down with fine wet or dry carborundum paper. Solvent may be used as a lubricant and cutting agent then repaint as required.
Loss of Gloss
Loss of gloss
Cause
General loss of gloss caused by moisture or gases coming in contact with the wet or semi-set film during drying. This is particularly noticeable on exterior surfaces such as window sills when the work has been completed late in the afternoon or early evening, when the ambient temperature falls, and dew comes in contact with the surface. Internally, in areas such as kitchens or bathrooms when there is an increase in humidity, i.e. steam before the coating dries.
Also see: Chalking.
Remedy
Flat down and re-paint with a further coat of gloss.