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Mapei Primer G is a synthetic resin-based primer in water dispersion specifically engineered for substrate consolidation and porosity control in commercial tiling and flooring workflows. This light blue liquid forms a flexible, compact film that prevents the chemical reaction between cement aluminates and gypsum sulphates, effectively stopping the formation of ettringite which causes delamination.
By regulating substrate suction, it eliminates pinholing in self-levelling compounds and prevents shrinkage cracks in sprayable plasters. Mapei Primer G is certified GEV EMICODE EC1 Plus for very low emissions, making it suitable for use in unventilated interior environments.
Frequently Asked Questions
Can Primer G be used on anhydrite screeds before tiling?
Yes. Apply Primer G neat on anhydrite screeds to consolidate and prevent rapid water absorption before laying tiles with cementitious adhesives.
Can Primer G be applied with a spray?
Yes. It can be applied using a flat brush, roller, or spray pump. Ensure even coverage and allow to dry fully before the next step.
Does Primer G waterproof gypsum?
No. It reduces porosity but does not act as a waterproofing membrane. Avoid using where rising damp is present.
Applications & Benefits
| Application / Use Case | Key Benefit | Primary Trades |
|---|---|---|
| Treat gypsum or anhydrite substrates prior to tiling | Prevents sulphate–cement reactions and debonding; ensures reliable tile adhesion | Tilers, Builders |
| Prime cementitious substrates before self-levelling compounds | Reduces air bubbles and over-rapid drying; delivers a uniform, consolidated surface | Flooring Installers, Builders |
| Anchoring coat for gypsum-based spray plasters | Controls absorption to extend workability and help prevent shrinkage cracks | Plasterers, Builders |
| Between coats of smoothing/levelling compounds | Improves intercoat adhesion once the first layer is fully dry | Flooring Installers |
| Primer for wallpaper adhesives on gypsum walls | Reduces absorption and glue usage; makes future removal easier | Painters & Decorators |
| Treat chipboard, cement fibre boards, foamed concrete, renders before papering/painting | Provides uniform absorption for consistent finish quality | Painters, Builders |
| Prepare gypsum plasters prior to smoothing with cementitious products | Prevents ettringite formation and layer separation | Plasterers, Builders |
Applying Mapei Primer G: Enhanced Protocols & Best Practices
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Surface Preparation
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.
Pro Tip: Use a moisture meter to confirm gypsum substrates meet manufacturer’s humidity requirements before priming to prevent later debonding. -
Mixing & Dilution
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.
Timing: Apply mixed primer immediately; avoid letting it settle or separate. -
Application
Apply evenly using a flat brush, roller, or spray pump. Avoid puddling and ensure uniform coverage over the entire surface.
Timing: Allow to dry for 30 min (cement) or 30–60 min (gypsum) before applying self-levelling compounds, adhesives, or plasters.Pro Tip: In high-absorption substrates, apply a second coat crosswise after the first has dried for uniform consolidation.
Limitations & Safety
Product Limitations
Not suitable for external applications or areas subject to rising damp — may result in premature failure or delamination.
Do not apply onto magnesium substrates or in such quantity that a surface film remains. Excess film can inhibit bonding of subsequent layers.
Ensure substrate moisture content meets manufacturer’s specifications before priming to prevent blistering or loss of adhesion.
Safety & Handling Requirements
Personal Protective Equipment
Wear chemical-resistant gloves (nitrile or neoprene), safety glasses, and protective clothing when handling Primer G. Wash hands after use.
Ventilation Requirements
Although Primer G is very low VOC and non-flammable, work in well-ventilated areas where possible. In enclosed spaces, ensure adequate airflow until surfaces are dry.
Fire & Handling Precautions
Primer G is non-flammable and safe for use in closed, unventilated rooms. Keep container tightly closed when not in use and protect from frost during storage.
Emergency First Aid
Eyes:
Rinse immediately with plenty of clean water for at least 15 minutes and seek medical attention if irritation persists.
Skin:
Wash thoroughly with soap and water. Remove contaminated clothing and launder before reuse.
Inhaled:
Move to fresh air and keep at rest. If symptoms persist, seek medical advice.
Swallowed:
Do not induce vomiting. Rinse mouth with water and seek immediate medical attention.
Seek medical attention immediately in all cases of serious exposure.
Mapei Primer G Application Guide
Gypsum & Anhydrite Screeds
Surface Preparation
Ensure surfaces are dry, free from dust, oil, grease, and loose material. Sand smooth and glossy anhydrite surfaces and vacuum thoroughly before priming.
Primer required for optimal adhesion
Apply Primer G neat, with a flat brush, roller, or spray pump, ensuring full, even coverage.
Primer GCementitious Substrates
Surface Preparation
Substrate must be clean, sound and dry. Repair cracks using Eporip/Epojet where required. Remove laitance and weak surface layers by mechanical abrasion.
Primer required for levelling compounds
Dilute Primer G 1:1 with water and apply uniformly with a roller or brush.
Primer GGypsum Plaster & Chipboard
Surface Preparation
Remove dust and contaminants. If glossy, lightly abrade. Check moisture content is within manufacturer’s specification before priming.
Primer recommended for consistent absorption
Apply Primer G neat and allow to dry completely before subsequent work.
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