Stabilising: A solution or Not

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In the 1950’s a new, revolutionary, washable material was developed to replace the then traditional non or semi-washable coatings. It was called emulsion paint.
But, it was soon established that when this product was applied over our very old favourites, distemper and limewash­ based coatings, problems occurred.
The prime difficulties encountered were caused during the drying period of the emulsion. This often caused a breakdown within the layer of an underbound material such as distemper. To combat this manufacturers introduced an oil based primer which in the very early days was based on a standard varnish with viscosity adjustment.
This very thin coating was then applied by brush helped to consolidate the top layer of the underbound material, and when dry it proved a sound surface to accept this new emulsion coating
Very soon the name Stabilising Solution was understood, accepted and introduced into the glossary of paint terms.
Distemper and limewash coatings are still available and used mainly on listed buildings but are rarely found these days in the course of normal refurbishment work.
Today it is only when excessive coats of emulsion or similar paints
have been applied to underbound or weak surfaces that problems may arise. A breakdown of the dry paint film is generally associated with the film weight and ageing of the
coatings applied over this underbound preparation, certain areas remain powdery or friable, it is only then that the Stabilising Solutions are recommended.
The term ‘to stabilise’ is often taken out of context. The need is often felt to ‘stabilise’ unpainted surfaces such as sand and cement render or paint coatings which are defective but not underbound.
This is wrong. In the majority of cases unpainted surfaces are not considered to be underbound or friable. Since the introduction of emulsion paints most surfaces which require re-painting, even though a breakdown may have occurred, do not require treatment with stabilising solution. As always there are exceptions to the rule, and manufacturer’s recommendations should always be followed.
Care should also be taken when bricks, particularly flettons, concrete and other non­ porous surfaces are to be decorated.
The history associated with these illustrations is that the walls were sand: cement rendered onto an insulating block. Because of the combined construction, there was a difference in thermal movement. Consequently fine hairline cracks appeared in the rendered surface. At site level, it was decided that the uncoated, rendered walls should be painted, but first stabilised. It was believed that by sealing the surface with stabilising solution the problem of cracking would be reduced and a good surface would be provided for a water ­ based masonry paint.
When the stabilising solution was applied to this non-porous surface it remained in a glossy condition. This can also occur when previously painted surfaces are treated in the same way.
Under these conditions, when overcoated with water-based masonry paints the adhesive properties are questionable.
The problem illustrated in this article was directly associated with this, as the adhesion of the water ­ based masonry paint over this glassy film was poor. During periods of prolonged wetting the water based coating took up moisture and caused the paint film to swell. This moisture uptake was so much that the film sagged and when the weather changed, the film dried back exposing the stabilising solution.
Because of this, the major cost associated with the remedial works involved the removal of water­ based masonry paint back to stabilising solution. This was then re-coated with an oil-based masonry system which has proved to be totally successful.

Even today, examples of the same problem can be found and the illustrations shown include a situation recently found within a public building where over the years emulsion based products have been applied over an underbound coating.

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