Epoxy, polyester, epoxy acrylate or PU

Choose the right glue

1. Polyester: The fast filler for indoor use

Polyester (often in solid 'knife-grade' or liquid form) is the traditional choice for the stonemason. It hardens very quickly and can be finished perfectly smooth.

  • Application: Filling holes (e.g., Travertine), repairing cracks in marble and limestone, and light assembly work indoors.

  • Note: Polyester can yellow over time and shrinks slightly during curing. Do not use outdoors, and preferably not on white marble (due to discoloration risk) or ceramics (insufficient adhesion).

  • Summary: Fast, cheap, and easy, but strictly for indoor use.

 

Instructions: Mix the glue with 1% to 3% hardener paste. Mix well until a uniform colour is achieved. Process the mixture quickly (within 5-10 minutes), as curing begins immediately.

 

2. Epoxy Acrylate: The "Rapid Epoxy"

Epoxy acrylate combines the speed of polyester with the strength of epoxy. It is often the favourite for production environments (such as making kitchen countertops).

  • Application: Mitre bonding, gluing composite and hardstone, and assembly where speed is important.

  • Advantages: Cures within 15-30 minutes, very strong, and much more colour-stable than polyester. Excellent polishability to high gloss.

  • Summary: The ideal production adhesive: Fast, strong, and clean finishing.

 

Instructions: Mix the glue with 1% to 3% hardener paste (in cans) or use a mixing nozzle (in cartridges). Ensure a clean, dry surface. After curing (approx. 20-30 min), the material can be sanded and polished immediately.

 

3. Epoxy (Pure): For the heaviest and most difficult jobs

Pure epoxy adhesives are the problem solvers. They have a longer drying time but offer the very best adhesion, especially on dense materials that do not "absorb" anything.

  • Application: Bonding ceramics and Dekton (polyester does not adhere here!), outdoor applications (frost/heat resistant), and laminating different types of stone.

  • Advantages: Does not shrink (so no tension on the stone), barely yellows (if UV-stable variant), and is weather-resistant. Unique advantage: This is the only type of glue that adheres to a (slightly) damp surface.

  • Summary: Indispensable for ceramics, outdoor work, and light-coloured stones.

 

Instructions: The mixing ratio is crucial (often 2:1 or 1:1, see packaging). Weigh component A and B exactly and mix until no streaks are visible. The processing time is long, but full curing often takes 12 to 24 hours.

 

4. Polyurethane (PU): Construction Strength & Outdoor Bonding

Polyurethane adhesives (PU) are powerful 2-component adhesives that we distinguish into two specific types for the stone sector:

  1. Aliphatic PU (such as Akemi EVERCLEAR): High quality, UV-stable, and frost-resistant. Ideal for visible outdoor work and light-coloured stones.

  2. Aromatic PU (such as Akemi AKEPUR): Fast-curing and extremely strong. Ideal for constructive work (bonding reinforcement profiles underneath) that is not directly exposed to sunlight or moisture.

  • Application: Outdoor bonding of ceramics (Everclear), repairs, and large-area bonding of reinforcement plates or profiles (Akepur).

  • Advantages: High structural strength, impact-resistant, and excellent filling capacity to bridge gaps. Because PU does not shrink during curing, it is (depending on the type) fully frost-resistant.

  • Note: The Everclear series does not yellow and can be used outdoors. The Akepur series is not UV-stable (yellows) and must not get permanently wet.

  • Summary: The specialist for structural reinforcement and weather-resistant repairs outdoors.

 

Instructions:

  • Colouring: Do you want to colour the glue? First mix the Polyester colouring paste (max 5%) into Component A. Only then add Component B; the colour tone will not change afterwards.

  • Mixing: Strictly respect the mixing ratio (often 1:1 or by weight).

 

General Guidelines & Disclaimer

For an optimal result, preparation is just as important as the choice of adhesive. Keep the following basic rules in mind:

  1. Cleaning: Always ensure a dust-free and grease-free surface. Use a suitable cleaner (such as acetone or a special cleaner). A dusty or greasy layer causes adhesion failure.

  2. Moisture: For Polyester, Epoxy Acrylate, and Polyurethane, the stone must be absolutely dry. Is the surface damp? Then use Epoxy exclusively.

  3. Roughening: Smooth surfaces (such as the back of ceramics or polished sides) must be slightly roughened/sanded to enable mechanical adhesion.

  4. Safety: Always wear suitable protection (gloves and safety glasses) and ensure sufficient ventilation during processing.