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Transforming an absorbent gypsum, cementitious, or anhydrite surface into a perfectly prepared substrate can be the difference between a lasting finish and costly rework. Primer G delivers consistent, uniform absorption and enhanced adhesion, ensuring subsequent finishes — from tiles to paint — bond reliably. It stabilises challenging substrates, eliminating common issues before they start.
Primer G is a synthetic resin primer in water dispersion, specifically formulated to consolidate and prepare absorbent surfaces. It addresses the critical need to regulate absorption and improve adhesion on tricky substrates like gypsum, cement, and anhydrite. This primer acts as an essential barrier, preventing detrimental chemical reactions such as ettringite formation between gypsum and cement-based products. Its purpose is to ensure any subsequent finish, from ceramic tiles and smoothing compounds to wallpapers and paints, achieves optimal bond strength and performance.
Primer G’s 18% dry solids content ensures it forms a flexible, compact coating without creating a thick surface film, which is crucial for uniform absorption. With a drying time of 30-60 minutes on most substrates, it allows for quick turnaround, keeping projects on schedule. Classified as EC1 Plus for very low emissions and containing 0 grams per litre of Volatile Organic Compounds (VOCs), it promotes healthier indoor air quality, making it suitable for use in enclosed, unventilated spaces without special precautions.
Primer G serves as a foundational preparation step, typically applied directly to the substrate after cleaning and repairs. It creates the critical interface that ensures compatibility and robust adhesion for subsequent layers. For multi-layer systems, such as when applying several coats of smoothing compounds, Primer G can be diluted 1:1 with water and applied between layers once the previous coat is dry, guaranteeing consistent absorption and system integrity through the entire build-up.
Primer G is certified EC1 Plus (very low emission) by GEV EMICODE, ensuring it contributes to superior indoor air quality during and after application. This standard provides peace of mind for both applicators and building occupants.
Primer G is specifically engineered for consolidating and regulating the absorption of highly porous surfaces like gypsum, cement, and anhydrite. Its primary role is to ensure uniform absorption and prevent chemical reactions, making it ideal for preparing these challenging substrates for subsequent finishes. In contrast, Eco Prim Grip is a versatile, ready-to-use primer designed to enhance adhesion on both absorbent and non-absorbent, smooth surfaces. While Eco Prim Grip offers exceptional grip, Primer G's focus on absorption control and consolidation on problematic porous substrates defines its unique value in the Mapei primer range. Choose Primer G when absorption regulation and substrate consolidation are key, and Eco Prim Grip when strong adhesion to diverse, potentially non-absorbent surfaces is the priority.
Primer G prevents a chemical reaction between sulphates in gypsum and cement aluminates, which can form "ettringite" and cause delamination. It forms a barrier, ensuring a stable bond.
No, Primer G is not recommended for external use or where rising damp is present. It is designed for internal applications and will not prevent water ingress or perform reliably in damp conditions.
The drying time before applying levelling compounds or adhesives is 30 minutes on concrete substrates. For gypsum substrates, allow 30-60 minutes, assuming 23°C and 50% relative humidity.
It reduces the formation of air bubbles in the compound and prevents over-rapid drying of the leveller. This extends workability and simplifies the self-levelling process for a smoother finish.
| Application | Key benefit | Primary trades |
|---|---|---|
| Preparing gypsum for ceramic tiling | Prevents ettringite formation and delamination between gypsum and cementitious tile adhesives. | Tilers, Floor & Wall Preparers |
| Priming before self-levelling or smoothing compounds | Reduces air bubbles and prevents premature drying, improving workability and finish quality. | Floor Preparers, Tilers |
| Anchoring coat for gypsum-based sprayable plasters | Regulates substrate absorption, prolongs workability, and helps prevent shrinkage cracks. | Plasterers |
| Fixative for wallpaper or paint on gypsum walls | Uniformly reduces substrate absorption, reducing glue consumption and easing future wallpaper removal. | Painters, Wall Paperers |
| Between layers of smoothing compounds | Ensures consistent absorption and adhesion for subsequent layers, maintaining system integrity. | Floor Preparers |
Ensure the surface is structurally sound, dry, and free of oils, grease, paint, or dust. Sand anhydrite surfaces, vacuum thoroughly, and repair cracks if required.
Stir well before use. Dilute Primer G as follows: 1:1 with water for cementitious substrates, 1:2 for anchoring gypsum plasters, 1:3 for wallpaper primer. Apply neat on gypsum-based substrates.
Apply evenly using a flat brush, roller, or spray pump. Avoid puddling and ensure uniform coverage over the entire surface.
Mapei Primer G is not classified as dangerous according to Australia WHS 2 (2021).
Eye protection is not required for normal use. Operate according to good working practices. Suitable materials for safety gloves include Nitrile rubber (thickness >=0.35mm, breakthrough time >=480min) or Butyl rubber (thickness >=0.5mm, breakthrough time >=480min).
Primer G is non-flammable and can be used in closed, unventilated environments without special precautions.
Store in original unopened packaging for up to 12 months. Protect from frost. Keep away from food, drink, and animal feed in adequately ventilated premises. Dispose of product and contaminated packaging according to local regulations; do not dispose into drains or waterways.
Proper substrate preparation is critical for adhesion and system performance. This guide details specific prep and priming instructions for common surfaces.
Surface prep: Substrate must be clean, dry, and free from oils, grease, residual paint, and loose material. Follow manufacturer's recommendations for moisture content and surface finish. Abrade particularly smooth or glossy gypsum plaster surfaces.
Primer: Required. Apply neat (undiluted) for smoothing compounds or use undiluted for ceramic tiles. Dilute 1:2 with water for anchoring gypsum plasters. Dilute 1:3 with water for wallpaper adhesives.
Surface prep: Must be clean, dry, and free from contaminants. Repair cracks with a suitable product like Eporip or Epojet. Ensure surfaces are sound and free of loose material.
Primer: Required. Dilute 1:1 with water before applying smoothing or thixotropic compounds. Use undiluted if applying gypsum-based products over cementitious renders.
Surface prep: Sandpaper the surface thoroughly before application to ensure proper adhesion.
Primer: Required. Use Primer G undiluted before applying cement-based products or when installing ceramic tiles with cementitious adhesives.
Surface prep: Ensure surfaces are clean, dry, and structurally sound, free from dust, oils, and loose particles.
Primer: Required. Apply Primer G as a fixative prior to papering or painting, typically diluted according to absorption.
| Property | Value |
|---|---|
| Consistency | liquid |
| Colour | light blue |
| Density | 1.01 g/cm³ |
| pH | 8 |
| Dry Solids Content | 18 % |
| GEV EMICODE | EC1 Plus - very low emission |
| Maximum VOC (2004/42/EC) | 0 g/l |
| Application Temperature Range | 5°C to 35°C |
| Drying Time Before Levelling Compounds or Adhesive (Concrete) | 30 min |
| Drying Time Before Levelling Compounds or Adhesive (Gypsum) | 30-60 min |
| Consumption | 0.08 - 0.15 kg/m² |
Here are some common examples on where Mapei Primer G used by our customers.
Masonry
Applying sprayable gypsum plaster, wallpaper, or paint onto absorbent internal gypsum or cement fibre walls.
Regulates substrate absorption, preventing rapid water loss from plasters, reducing glue usage for wallpaper, and improving finish consistency.
Tiling
Installing ceramic tiles or cementitious smoothing compounds onto gypsum plaster or anhydrite screeds.
Prevents delamination by stopping ettringite formation, ensuring strong adhesion for cement-based products on sulphate-rich substrates.
Flooring
Preparing cement-based substrates before applying self-levelling or thixotropic smoothing compounds.
Reduces air bubble formation and prevents over-rapid drying of levelling compounds, ensuring a smoother, more even floor finish.
Painting & Decorating
Treating porous surfaces like gypsum walls, chipboard, or renders prior to wallpapering or painting.
Provides uniform absorption for consistent finish quality, reduces wallpaper adhesive consumption, and simplifies future wallpaper removal without damage.
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