White Patches + Spots

Common causes and solutions to prevent and fix white patches and spots on a limewash finish

Words
© Andreas Riedel
Published
2024.08

Q. I have finished painting my walls with Bauwerk Limewash Paint–what are the 'white patches' I can see?

White patches or spots usually appear when limewash paint is applied too thickly, preventing it from curing properly. This causes the lime to ‘bloom’ on the surface, leaving white patches and making it powdery, so it comes off easily when touched. For best results, apply limewash in thin coats using an absorbent bristle brush.  Spread the paint out as far as it will go, without overworking it. Curing takes about two weeks, so avoid rubbing the walls during this time to prevent marking.


Mineral-based limewash, like Bauwerk Colour, requires a moderately absorbent surface. When a surface is non-absorbent or absorbs too little, proper preparation must be undertaken to create the right conditions for the limewash paint to penetrate. If painting over a sealed or non-absorbent surface, such as a wall previously painted with standard acrylic house paints, lime blooming is more likely to occur, as it is more difficult to avoid over-application of limewash. We recommend using Bauwerk Prep Coat as an important step in surface preparation when limewashing previously painted or sealed interior wall surfaces. For external surfaces that have already been painted or sealed, we recommend applying a fresh cement-based absorbent thin coat render (used externally or internally) to create a surface for limewash paint to penetrate.

Bauwerk Colour Limewash paint white patches and how to fix


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3 Common Causes for White Patches + Spots
Painting a Bauwerk Colour Sample Pot
Application
Using Too Much Paint
White patches usually appear when paint is too thickly applied. The best results are achieved using thin applications rather than thick coats.  Bauwerk Limewash cures by taking carbon dioxide from the air, a truly wonderful and natural occurring process. The thin coats allow the right amount of curing. If the paint is too thick, than the paint cannot cure correctly and it leaves white patches and makes it powdery to the touch. This can be easily fixed by waiting 24 hours and then applying another thin coat.  Note: It is best to go back and reapply Prep Coat if you have already done 4 or more coats of limewash paint. 
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Limewash Paint Brushes
Tools
Not Using the Correct Brush
Using a natural fibre brush that is well cleaned with supple bristles will help to leave minimal brush marks and give the most even finish. You may get away with using a conventional brush on a nice absorbent substrate but you will use much more product than needed. Using a conventional brush on a sealed or Prep-Coated surface will give a very poor looking finish. 
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Paint Roller for Prep Coat
Preparation
Improper Wall Preparation
Depending on the material and condition of your interior wall surface, you may need to apply Bauwerk Prep Coat before limewashing. Skipping this step when necessary or applying it incorrectly can lead to an inconsistent finish. Applying Prep Coat consistently across a surface is essential for ensuring the best final paint finish. It creates an absorbent layer that allows the limewash to adhere properly, adding durability and preventing over-application. However, an inconsistent application of Prep Coat can lead to varying levels of absorbency across the wall, resulting in visible patches where the color changes due to these differences. If you notice roller lines or straight-edged patches on your finished wall, this indicates a patchy Prep Coat layer. This issue is more pronounced with darker limewash colors. To fix patching caused by inconsistent Prep Coat application, we recommend applying another coat of Bauwerk Prep Coat over the wall before reapplying limewash.
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Q. How do I fix my limewashed wall that has white powdery patches or spots?

Fix 1. To cover white patches from over-application, simply wait 24 hours and apply an additional thin coat of limewash paint. 

  • Our paint must be applied by spreading it as far as it will go without overworking it. When painting your clouds, make sure to paint until it feathers out on the edges. This is a good indicator that the paint has been stretched.
  • A quick tip to ensure your coats are consistent is to have a look side-on from where you have just painted. With the glare, you can see if there are areas with too much product.
  • Be mindful to have the "right" amount of paint on your brush for the area or cloud you will be painting. Too little will also make it difficult to spread before it dries.  Dip the brush 2.5 cm into the limewash, flick it once with your wrist into the bucket, and then you are good to go. This amount of paint should cover around one square meter of wall over the Prep Coat.


Fix 2. Using a bucket of clean water, dip your brush 1cm into the water, after every 3- 4 times that you have taken limewash paint onto your brush. This helps stop the edge of your paint from drying too quickly.


Tip: Make sure your limewash brush is in good condition – not too dried out and clean of old paint etc. 

More Tutorials + Advice

Check out our YouTube channel for videos. Our Surface Guides also offer great tips for your wall material.

Troubleshooting white patches on limewash paint and how to fix it

Q. How can I prevent white patches from appearing in my limewashed wall?

Checklist for preventing white patches on your limewash finish

  • Brush Condition: Ensure your limewash brush is in good condition, well-cleaned, and with bristles that are not too dried out.
  • Paint Consistency: Paint must be well stored and sealed to prevent evaporation.
  • Proper Stirring: Stir well, with a whisk or a mixer–not with a stick. Decant your paint into another bucket to keep the consistency uniform. Only well-stirred paint will give a good finish.
  • Weather Considerations: Avoid painting in extreme weather, whether too hot or too cold. Ideal painting temperature: 8 – 30°C (45°F – 85°F) and at least 5°C (40°F) during application or curing.
Bauwerk Colour Limewash Paint stirred with a Whisk
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