St. Leo Bio Undercoat

St. Leo Bio Undercoat

Bio Undercoat is the recommended preparation layer for normally absorbent substrates ahead of St. Leo Bio Paint. Available in three tones matched to light, mid, and dark Bio Paint shades, it ensures strong adhesion and lets Bio Paint show its full colour depth and saturation.

Bio Undercoat is a highly effective transition layer, evening out sharp colour contrast between substrate and topcoat for uniform coverage, a consistent finish, and optimal hiding power.

Features

• Ensures strong adhesion, full colour depth, and more efficient paint use
• Three tones, matched to light, mid, and dark topcoats
• Excellent coverage
• Highly breathable, helping prevent condensation within the wall
• Very low VOC emissions, kind to indoor air quality
• Smooth to apply, with minimal dripping or spatter
• Plant-based eco binder
• Virtually odourless
• Water-based, free of harmful solvents
• No added acrylics, plastics, microplastics, plasticisers, or synthetic resins
• Vegan formula, naturally biodegradable

Technical specifications

• Suited for: interior walls and ceilings
• Sheen: Gloss 2
• Dry time (23°C / 50% humidity): touch-dry and recoatable in 4–6 hours
• Application temperature: +8°C to +30°C
• Application humidity: ideal 40–65%, maximum 80%
• Tools: roller, brush, airless spray
• Dilution: ready to use, or thin with up to 10% water if needed
• Packaging: 5L, 10L (10L for professional use only)
• Coverage: approximately 8–10 m² per litre per coat; 1–2 coats recommended
• VOC content: max 1 g/L (EU Cat. A/a limit: 30 g/L)

Choosing a tone

• White & light Bio Paint shades → use White & Light Tones
• Mid-tone Bio Paint shades → use Mid Tones
• Dark Bio Paint shades → use Dark Tones

Before you start

For highly or unevenly absorbent substrates (fresh plaster, concrete, plasterboard, or heavily patched walls), apply Bio Micro Primer first, then Bio Undercoat. For normally absorbent, well-prepared walls, Bio Undercoat can be applied directly.

Application notes

Stir thoroughly before use to ensure even pigment distribution. If a single tin won't cover a continuous wall, box multiple tins together first. Apply a single coat with a medium-pile long roller, brush, or airless spray — avoid building up excess thickness. For best results, use the same type of applicator planned for the Bio Paint topcoat. Keep the space well ventilated; Bio Undercoat is touch-dry and recoatable after 4–6 hours.