INFORMATION SHEET
SS-131
Revised June 2015
TREATMENT OF POWDERY SURFACES – PLASTER, KALSOMINE AND EFFLORESCENCE
Flaking is often caused by lack of adhesion or breakdown between earlier coats of paint, or failure of the substrate
itself. In some cases this can be due to chalkiness, powderiness or efflorescence. If the system breakdown is
properly assessed, the correct preparation can be employed and the best results can be obtained when rectifying.
On close examination the coating may be powdery on the surface or showing signs of weak adhesion due to
powderiness beneath the paint. A simple way of testing this is to stick approximately 150 mm of 25 mm clear
cellulose tape firmly to the surface. Remove by tearing off very quickly and ascertain the extent to which, loose
powder or flakes of paint or substrate material are removed. If no material comes away with the tape then the
surface is usually considered sound. On the other hand, if some material is removed by the tape then specific
preparation is usually required. This may be common in old buildings where there may be many coats of paint,
each with deteriorating adhesion over the years. Stresses of a new coat of paint can pull the whole system away,
therefore, proper preparation is essential. In some cases the tape test may indicate a failure beyond a Master
Painter's responsibility to remedy, (e.g. removal of plaster layers or render coat on bagged walls, etc).
If the existing coating is cracking or flaking, it should be removed by scraping and rubbing back to a sound surface
and the substrate then checked for any chalkiness or powderines. If the surface is chalky or powdery, all the loose
powder must be completely removed. If some chalk remains after thorough cleaning by scraping, washing, rubbing
down etc, a surface binder should be applied to the dry surface. SOLVER Line 4104 Surface Conditioner is a
penetrant material that is capable of binding and sealing back loose surface material. It is useful in assisting to
overcome a problem, but is not necessarily a "cure all" and is certainly not an excuse for poor cleaning down or
where heavy layers of chalk still exist. At the best it provides the maximum adhesion possible under adverse
conditions and the property owner should be advised of any potential issues.
KALSOMINE
Kalsomine is a loose powdery material that consists of a pigment bound with a water soluble casein glue, which is
then mixed with water prior to use for application onto ceilings and walls in the 1950 to early 1960’s. It is not a
suitable material to support further coats of modern paint materials and must be completely removed. In some
cases, Kalsomine may be present beneath the previous paint layer and can become problematic when attempting
to roll on any subsequent coats of paint. The combined action of roller surface tension, water in the new coating
and stresses in applying the new finish can work up the existing coating system and large scale blistering can
result.
To remove, washing with warm water and coarse, open weaved fabric such as cotton singlets, cheese cloth or
hessian bags is necessary. Rinse out thoroughly and change water frequently. Continue to wash until no further
powder is removed. If using hessian, dust off the surface thoroughly after washing and drying to remove small
hessian fibres from the surface which may be evident in the subsequent dried paint film. Allow surface to dry
thoroughly, then apply one coat of SOLVER Line 4104 Surface Conditioner and allow to dry for a minimum of 24
hours if applying a solvent based topcoat and a minimum of 48 hours if applying water based material.
PLASTER
In the case of soft plaster, detected by being able to easily scratch the surface with a finger nail, the wall should be
treated with a 14% solution of phosphoric acid. The acid reacts with the surface, dissolving the loose surface layer
and the subsequent solution is absorbed back into the wall leaving a firm surface ready for painting when dry. If the
plaster has been painted previously and the paint is failing, the paint layers will need to be removed to allow
penetration of the acid solution into the plaster surface.
For preparation of new plaster please refer to Information Sheet SS-108 “Preparation of New Plaster Substrates”.
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INFORMATION SHEET
SS-131
EFFLORESCENCE
Efflorescence is identified as a loose, white, fluffy surface powder and is more frequently found on Gypsum plaster
walls than on fibrous plaster and usually consists of Sodium Sulphate which may have been present in the material
used in the construction of the wall. All new masonry walls contain moisture and soluble alkaline salts (both in the
rendering and/or the plaster coat) and Efflorescence can be formed by chemical reaction between them and the
plaster. As the wall dries, Sodium Sulphate in solution is transported to the surface, where it is deposited as a
bulky white precipitate when the water evaporates. If walls are painted before they are suitably dry, the efflorescent
salts may crystalise on top of the paint film or form beneath and lift it.
The treatment of Efflorescence depends upon the nature of the deposit and chemical analysis is necessary to
establish its composition. It is therefore advisable to seek expert advice if failures of this kind occur. However, as a
general practical guide, most cases of Efflorescence are remedied by the following treatments:If the surface has been painted and the film is adhering well a sufficient treatment is to wipe off the Efflorescence
with a dry cloth and remove the last traces with a damp cloth. If the wall is thoroughly dry and remains so, then no
further Efflorescence will occur. If the paint is peeling, all the loose film should be removed by scraping, and the
surface should be treated with a 15% solution of Calcium Chloride before repainting. Two coats of this solution are
necessary with an interval of about 2 hours between them and the surface can be painted about 24 hours after the
application of the second coat. Calcium Chloride inhibits Efflorescence by reacting with the Sodium Sulphate and
converting it into Sodium Chloride, which is less undesirable from this point of view.
Painting should be deferred until the walls are considered to be dry. The best way of assessing this is by
conducting a moisture meter test and until the moisture content of the wall is below 16%, painting should not
commence.
For specific advice relating to your individual project, please phone our INFORMATION HOTLINE: Ph: 132101
(AUSTRALIA)
1. This information is provided with respect to the listed Solver products. Valspar (WPC) recommends that:
(a) you review the Technical Data Sheets (TDS) and Safety Data Sheets (SDS) before you use or handle the product; (b) the product be used only in accordance with
the information provided by Valspar; (c) the product be transported, stored and handled in accordance with the information on the SDS and relevant TDS; and (d) you
thoroughly test the product, using the recommended application method on a sample of intended substrate, before using the product.
2. The information in this specification sheet was prepared using information gathered during product development. While Valspar endeavours to update this information
and maintain the accuracy and currency of its contents, Valspar cannot guarantee that the information provided is wholly comprehensive.
3. Valspar recommends that you conduct such additional investigations as may be necessary to satisfy yourself of the accuracy, currency and comprehensiveness of the
information on which you rely in using and handling the product. If you require further information please contact your nearest Valspar Office.
4. To the full extent permitted by law, Valspar’s liability for breach of a condition or warranty implied into the contract for sale between Valspar and you by law is limited
at Valspar’s election to: (a) the replacement of the product; or (b) payment of the cost of replacing the product.
Wattyl, Granosite are registered trademarks of Valspar Paint (Australia) Pty Ltd ABN 40 000 035 914. Solver, Solver Ultra are registered trademarks of Valspar (WPC)
Pty Ltd ABN 65 007 527 371.
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