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.

Why this product exists

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.

The numbers that matter

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.

What it's like to use

• Substrate Preparation: Surfaces must be clean, dry, and free from loose material. For concrete with cracks, repairing with Eporip or Epojet is recommended before priming. Anhydrite surfaces require sandpapering.
• Application Versatility: Primer G adapts to various application needs. Use it neat for ceramic tiles on gypsum or for self-levelling on gypsum-based substrates. Dilute it 1:2 with water for anchoring gypsum plasters, 1:1 for self-levelling on cementitious substrates, and 1:3 for wallpaper adhesives. Always apply with a flat brush, roller, or spray for uniform coverage.
• Clean-up: Tools and containers clean easily with water immediately after use. Dried residues can be removed mechanically or with Pulicol 2000.

Where this product excels

• Tiling over Gypsum: Essential for preparing gypsum plasters, panels, or anhydrite screeds before installing ceramic tiles. It prevents the chemical reaction that causes delamination, ensuring the tile adhesive bonds securely.
• Flooring Underlayment: Used before applying self-levelling or smoothing compounds on cementitious or gypsum floors. Primer G reduces air bubbles, prevents premature drying, and improves workability, leading to a smoother finish.
• Wall & Ceiling Finishing: As an anchoring coat for gypsum-based sprayable plasters, it regulates water absorption, extends workability, and minimises shrinkage cracks.
• Painting & Decorating: Ideal for priming gypsum walls, chipboard, cement fibre boards, or renders before painting or wallpapering. It reduces absorption uniformly, decreases glue consumption for wallpaper, and simplifies future removal.

How it fits in a real system

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.

Choose this when

• When preparing absorbent gypsum, cementitious, or anhydrite substrates: For uniform absorption and optimal adhesion of ceramic tiles, smoothing compounds, sprayable plasters, wallpaper, or paint.
• When preventing ettringite formation: Essential between gypsum and cementitious products to avoid delamination.
• When regulating substrate absorption: Critical for extending the workability of plasters and reducing consumption of wallpaper adhesives.
• When seeking a low-emission, non-flammable primer: Ideal for enclosed interior applications where air quality is a concern.

Don't use this when

• Not for: Waterproofing gypsum substrates; this primer reduces porosity but does not provide a waterproof barrier.
• Not for: Magnesium substrates, as it is not formulated for adhesion to these materials.
• Not for: External applications or areas with rising damp, where its performance and durability may be compromised.
• Not for: Applying as a thick, undiluted surface film across all applications; follow dilution ratios to achieve the correct film thickness and optimal absorption regulation.

Primer G versus Mapei Eco Prim Grip

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.

Related products

• Mapei Eco Prim T Plus