How To: Working With Epoxy In Warm Weather – Top Tips

It’s that time of year when we are able to get on with DIY tasks and hobbies during the glorious sunshine and whilst the weather is warm. There are projects that need starting, and some that need finishing… but what can you do to get the most from epoxy when working in warm weather.

Although epoxy prefers warmth over colder temperatures as with cooler temperatures, warmer temperatures and humidity can cause curing issues affecting optimum results.

What do we mean by warm? Our data sheets always state handling characteristics (pot life) at 21˚C and cure to solid state at 25˚C. Whilst WEST SYSTEM 105/205 will cure right down to 5˚C. In truth a temperature above 15˚C is ideal but as the temperature rises to or above 25˚C the following tips should enable good results. T-shirt wearing temperature is a good indicator of a sound working environment where you might notice cold or warm surroundings.

Epoxy resin is mixed with a compatible epoxy hardener in a precise ratio to start the curing process, the result being a rock-solid thermoset plastic that is strong and resilient. Trying to mix epoxy in temperatures above room temperature is a quick-fire way to kickstart the curing process, the higher the temperature, the quicker the mixed epoxy will cure.

Did you know: Humidity can cause a cloudy look and oily like appearance on the surface due to the moisture within the environment.

Referred to as amine blush this can be removed easily with clean water and white paper towels.

To understand why it is important to work within the right temperatures let’s talk about the three stages of a cure.

1: Liquid (Open time)

This is when you have mixed the epoxy resin and hardener together and the result is a workable liquid. This is the time window you have to mix any additives and do any spreading or clamping. The warmer it is, the quicker the liquid will enter the next phase.

2: Gel (The initial cure phase)

The epoxy is no longer workable and will progress from a tacky gel consistency until the mix becomes ‘rubbery’. You can still dent it with a fingernail, but the mix is no longer fluid and too soft to sand, although it will remain as tacky as masking tape for a while. When used as a coating this ‘tackiness’ can be used to form a chemical bond with a fresh layer, making a stronger bond.

3: Solid (Final Phase)

The epoxy has cured into a solid. Now it can be dry sanded or shaped but won’t form a chemical link to any fresh epoxy – so the surface must be thoroughly washed and sanded before recoating to achieve a good mechanical, secondary bond. Sanding increases the surface area to create a key for a mechanical bond instead. In reality, the epoxy mix is 90% cured and will achieve full hardness over the next couple of days at room temperature.

Consequences of warm epoxy

Shortened pot life.
Greater risk of run-away exotherm.
Risk of drain out if laminating fabric on a vertical surface.
Potential for slumping of fillets as epoxy starts to gel.

Advantages of warm epoxy

Lower viscosity will wet out fabrics quicker and will brush/roller out thinner coatings.
Lower viscosity mixed epoxy will soak into wood grain and wick into exposed glass fibres on a GRP surface prepared for a repair.
Faster dispensing with pumps.
Efficient blending of resin, hardener and additives.

TOP TIPS:

Keep a thermometer close by so you can ensure the epoxy is within the right temperature limits.
Keep the air flowing through, open windows and let as much air come in to cool the room down. Keep mixing pots and roller trays away from direct sunlight.
Never use epoxy that has been in the sun for a prolonged period of time, for example next to a window with sunlight bearing in, in a hot car, or outside.
Use a slower curing hardener to provide a longer working time
Mix small quantities at a time.
Plan your work session accurately and have all the materials to hand; work smart and swiftly

If you have any questions when you are using our products in warmer weather, please do get in contact techinfo@wessex-resins.com

If you have any exciting projects you are working on this summer, please don’t forget to tag us in your social media posts so we can see. If you would like to showcase your summer project, then do fill in our form and get involved with our next Epoxycraft article.