HARDENER Guide
When working with epoxy resin, the choice of hardener is crucial in determining the final properties of your project. The right hardener can significantly impact factors such as cure time, strength, and durability.
Key Considerations for Hardener Selection
Cure Speed: How quickly do you need the epoxy to set? Fast-curing hardeners are ideal for small projects or repairs, while slower-curing options are better suited for larger applications or tasks that require extended working time.
Temperature: Consider the ambient temperature where you’ll be working. Some hardeners are more temperature-sensitive than others, so it’s important to select one that performs optimally in your environment.
Application: The intended use of the epoxy will influence your hardener choice. For example, bonding structural elements may require a high-strength hardener, while a decorative coating might benefit from a hardener that offers a clear, glossy finish.
Additives and Fillers: Certain additives or fillers can affect the curing behaviour of epoxy. Consult the product information for compatibility recommendations.
Understanding Hardener Speed
Each hardener possesses an optimal temperature range for curing. However, regardless of the temperature, every resin/hardener mix undergoes the same stages of curing. It is crucial to choose a hardener that provides sufficient working time for your project, considering the temperature and conditions in which the work will be carried out.
The WEST SYSTEM user manual and product guide includes detailed information about the pot life and cure times of each hardener. Pot life is a term used to compare the curing speeds of different hardeners. It refers to the duration that a specific quantity of mixed resin and hardener remains in a liquid state at a specific temperature.
The pot life is a measure of the curing speed of a specific volume of epoxy, not the working time of the epoxy mix. The working time can be less than the pot life, depending on the application and the volume used. So, it’s important to consider both factors when selecting a hardener for your project.
WEST SYSTEM 205 Fast Hardener®
The 205 Fast Hardener is typically the go-to choice when a quick cure is required. It forms a high strength, rigid solid with excellent cohesive properties and acts as an exceptional moisture vapour barrier with great bonding and coating properties. It has a pot life of 10 to 15 minutes at 25°C ( 77°F) and cures to a sold state in 5 to 7 hours*. The minimum recommended working temperature is 5°C ( 41°F).
WEST SYSTEM 206 Slow Hardener®
The 206 Slow Hardener is a low viscosity curing agent that forms a high-strength, rigid, moisture-resistant solid, making it excellent for use as a coating and bonding adhesive. It’s ideal for extended assembly times when working in optimal conditions. It has a pot life of 20 to 30 minutes at 25°C ( 77°F) and cures to a solid state in 9 to 12 hours*. The minimum recommended temperature is 16°C (60.8°F).
WEST SYSTEM 207 SPECIAL CLEAR Hardener®
The 207 Special Clear Hardener provides exceptionally clear moisture-resistant, and high-strength, properties perfect for coating and fibreglass cloth applications. If you are looking for an exceptionally clear finish this is the hardener to choose. The 105/207 mix provides a pot life of 25 to 30 minutes at 22°C. An ultraviolet inhibitor in the 207 helps enable a long lasting beautiful finish when used with a high-quality UV-filtering varnish. The minimum recommended temperature is 16°C (60.8°F).
WEST SYSTEM 209 Extra Slow Hardener®
The 209 Extra Slow Hardener is designed for use in extremely warm and/or humid conditions for general bonding and coating applications or when extended working time is desired at room temperature. A 105/209 mix provides approximately twice the pot life and working time of 206 Slow Hardener. The 105/209 mix has a pot life of 50 to 70 minutes at 25°C and working time of 50 to 70 minutes (thin film)*. It forms a clear amber coloured solid with good physical properties and moisture resistance for bonding and coating applications. The minimum recommended temperature is 18°C (64.4°F).
So, What hardener will you choose?
Overall, the choice of hardener depends on your specific needs such as desired curing time, working temperature, and whether you need a clear finish or not. Always ensure that the resin, hardeners and mini pumps are labelled with the same pack size letter when purchasing.
*Epoxy cures faster at higher temperatures and in thicker applications.
Please note: The mix ratios for our hardeners vary. Specifically, the 207 Special Clear Hardener and 209 Extra Slow Hardener require a mix ratio of 3 parts resin to 1 part hardener by volume. This is different from the 205 Fast Hardener and 206 Slow Hardener, which require a mix ratio of 5 parts resin to 1 part hardener.
Due to these differences, each type requires a compatible pump set that also matches the appropriate tin sizes. For more comprehensive information, we recommend referring to the Technical Data Sheet (TDS) section on our website.