Earthborn Bonding Primer

Earthborn Bonding Primer is a water-based, eco-friendly primer designed to improve paint adhesion and balance surface absorbency. Suitable for both interior and exterior use, it provides a reliable base for Earthborn Claypaint and Silicate Masonry Paint, helping to achieve a smooth, consistent and long-lasting finish.

Ensure all surfaces are sound, clean, dry and free from grease, dust, wax or other contaminants.

• Remove any loose, flaking or powdery paint to ensure a stable base
• Treat any fungal growth or mould with a scraper, followed by a suitable Fungicidal Wash or mould and mildew cleaner
• Fill cracks, holes or imperfections with an appropriate Multi Purpose Interior Filler or Ready Mixed Fine Surface Filler and allow to dry before sanding smooth
• Lightly sand glossy or previously painted surfaces to provide a key, then remove all sanding dust with a vacuum or damp cloth
• Surfaces must be dry and free from salts. Areas affected by rising damp or efflorescence should be treated and allowed to fully dry before application
• For paints applied before 1960, take extra care as they may contain lead-seek specialist advice and follow safety precautions when preparing these surfaces

Always carry out a small test area before starting to confirm compatibility, adhesion and final finish with the chosen top coat.

• Stir thoroughly before and periodically during use to maintain a smooth, even consistency
• Apply evenly with a high quality synthetic brush, roller, such as Osmo Premium Roller, Brush and Tray Set, or spray applicator, maintaining a wet edge to avoid lap marks
• For highly absorbent surfaces, the primer may be thinned with up to 5% clean water to aid application and penetration
• Apply in thin, even coats and avoid overworking the surface to prevent visible brush or roller marks
• Only apply when the ambient and surface temperature is above 8°C and below 25°C, avoiding direct sunlight, high humidity, or rain during drying
• Allow 6 hours before overcoating with Earthborn Claypaint or Silicate Masonry Paint, though ideally ensure full curing (around 24 hours) for best adhesion

Once fully dry, the primed surface can be finished with Earthborn Claypaint or Silicate Masonry Paint to achieve a durable, breathable coating.

• Avoid cleaning or washing newly painted surfaces for at least seven days to allow full curing and film strength to develop
• Inspect the surface periodically for signs of flaking, damp, or contamination that could affect long-term adhesion
• In areas exposed to high moisture or condensation, ensure adequate ventilation to prevent mould or peeling
• Any small touch-ups or repairs should be carried out using the same primer and paint system for a consistent appearance
• Tools and equipment can be cleaned immediately after use with warm, soapy water
• Store any remaining primer in its original container, tightly sealed, in a cool, frost-free place for future maintenance work

What does Earthborn Bonding Primer do?

It promotes strong adhesion and evens out differing levels of surface absorbency, creating a reliable base for a consistent finish under Earthborn Claypaint (interior) or Silicate Masonry Paint (exterior). It's water-based, low odour and suitable for both interior and exterior use.

Which surfaces is it suitable for?

Earthborn Bonding Primer can be used on sound, stable, previously painted substrates and poorly absorbent surfaces such as engineered brickwork, plaster and gypsum plasterboard. It also supports uncured lime plaster internally, evening out absorbency before applying Claypaint.

Which surfaces should I avoid?

Do not use on fresh, highly absorbent mineral surfaces such as new lime plaster, or on synthetic resin renders, latex paints, plastic, wood, metal or glass. Avoid water-repellent areas and surfaces affected by rising damp or salts until they are treated.

What coverage and drying times should I expect?

Coverage is approximately 4-7m² per litre. It is touch dry in around 1 hour and ready to recoat after 4-6 hours under normal conditions (20°C, 65% humidity). Drying times may vary depending on temperature and airflow.

How do I apply Earthborn Bonding Primer?

Stir thoroughly before use. Apply thin, even coats with a brush, roller or spray, keeping a wet edge to prevent lap marks. For very absorbent surfaces, thin with up to 5% clean water. Only apply when temperatures are above 8°C and avoid direct sunlight, rain or cold weather during drying.

Can I apply it by spray?

Yes. Earthborn Bonding Primer can be sprayed using airless equipment. Typical settings are around 120 bar with a 0.58mm (523 tip) nozzle and an appropriate filter. Always test a small area first to confirm flow, pattern and finish.

Is it breathable and low in VOCs?

Yes. It offers medium breathability with an Sd value of 0.35m and contains only trace VOCs (<0.1%), making it a healthier, eco-friendly choice for homes and heritage properties.

Are there any special preparation or safety notes?

Surfaces must be clean, dry and free from grease, dust and flaking paint. Treat mould or mildew with a suitable cleaner and allow to dry. Lightly sand glossy or previously painted surfaces to provide a key. Paints applied before 1960 may contain lead - seek professional advice and follow safety precautions when sanding or stripping these coatings.

How should I clean up and store the primer?

Clean brushes and rollers with warm, soapy water immediately after use. Store any remaining primer in its original, tightly sealed container in a cool, frost-free place. Do not pour leftovers down the drain - allow them to dry and dispose of in accordance with local regulations.