St. Leo Bio Micro Primer

St. Leo Bio Micro Primer

Bio Micro Primer is a breathable, water-based primer made entirely from natural raw materials, designed for walls and ceilings that are highly or unevenly absorbent. Its role is to even out the substrate's absorbency, so that whatever St. Leo undercoat, paint, or mineral finish follows can bond more smoothly, evenly, and reliably — improving the texture and consistency of the finished surface.

Features

• Evens out substrate absorbency, ensuring uniform application of undercoats, paints, and mineral finishes
• Economical — a small amount goes a long way
• Highly breathable, helping prevent condensation within the wall
• Very low VOC emissions, kind to indoor air quality
• Easy to apply by roller, brush, or spray
• 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: matte (dries clear)
• 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: mix 1:1 with water
• Packaging: 5L
• Coverage: approximately 20 m² per litre per coat, once diluted
• VOC content: max 1 g/L (EU Cat. A/a limit: 30 g/L)

Suited substrates

For interior walls and ceilings that are highly or unevenly absorbent, including plaster, mortar, plasterboard, and brick. Freshly skimmed walls must be fully dry before priming, undercoating, painting, or applying Dolomite Plaster — as a rule of thumb, allow around 7 days of drying time per 5mm of fresh skim coat. The substrate should be clean, dry, level, and free of loose material.

Application notes

Mix the primer thoroughly with water at a 1:1 ratio. Apply over large areas with a roller, brush, or spray, in 1–2 coats depending on the wall's absorbency. Allow it to dry fully before applying an undercoat, paint, or plaster. Avoid direct sunlight during application and keep the space well ventilated. Bio Micro Primer is touch-dry and recoatable after 4–6 hours.