Simple Water Absorption Test prior to the application of limewash paint

How to test if a surface has the right absorbency for lime wash paint application

Prior to the application of lime wash paint it is a good idea to do a simple and quick test to determine if your surface has the right absorbency for lime wash paint.

Differences in absorbency can make the finish look uneven or patchy. To eliminate any older surface repairs showing through the finished paintwork, or to eliminate the ''ghosting'' of the outlines of gypsum board / plaster board panels your wall surface must have equal absorbency. That is achieved by applying a water based drywall sealer /undercoat.

But how can you test the surface if you need to do that? You can do this simple test:

Simple Water Absorption Test

Purpose of Test:

  • to see what level of absorbency the surface has,
  • to see if there are absorbency differences in repaired areas,
  • to see if walls constructed out of gypsum board / drywall panels are sealed enough to avoid ghosting of the outlines the panels

    Materials needed:
  • Clean water,
  • a brush or damp sponge

    Test method:
  • Apply evenly some water across the surface you want to test.
  • Ensure you are applying the water across a repaired section or joints if you test on gypsum board / plaster board

  • if the water is not absorbed and dried across the applied surface slowly and evenly you have a sealed or low absorbing surface.
  • if the water dries very fast, but evenly you have a high absorption surface
  • if the water dies unevenly and shows the previous repaired spots or outlines for gypsum board you need to apply a water based sealer / undercoat to eliminate the absorption differences and to avoid ghosting.

    Here are some images of correctly prepared internal walls finished with lime wash paint:
Lime wash over gypsum plaster / board

What is important to know is that for a nice lime wash finish the lime paint requires an evenly absorbing surface with not too much and not too little suction.

With dry wall panel and gypsum board construction you usually have a absorption difference between the panels themselves and the panel joints that are filled up with a gypsum based filling compound. If that absorption is not equalised you can end up with ''ghosting''. By ghosting is meant that the outlines of the panel become visible after the painting is completed.

Here is a photo of what that looks like:

insufficiently prepared gypsum plaster board wall painted with lime wash paint

Ghosting is also possible if the entire area has been skim coated with a gypsum plaster coat.

But do not worry, with the right preparation ''ghosting'' can be avoided.

Refer to our detailed specifications for internal lime wash paint application.

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