Trade Secrets: TRADE SECRET: How to create the perfect epoxy coating on wood
WEST SYSTEM® epoxy is an invaluable resource for creating a clear coating that showcases both the beauty of the wood grain and gives you four times the thickness of a single coat of polyurethane. In just a few simple steps, you can achieve a beautiful, bubble-free wooden surface using epoxy resin.
Bubbles are a frustrating side effect of epoxy coating that can make your clear-coated wood finish appear unattractive and rough. It is important, therefore, to remove all the air bubbles before the epoxy gels as this can lead to the bubbles being trapped within the coating or popping and creating a sharp ridge.
Preparing the surface
To create a clear coating, it’s vital to prepare the surface thoroughly. Surfaces ready for coating should be clean, dry and free from any contamination. Then sand down the surface and vacuum up any extra dust to avoid any bubbles, blisters or other damage to the quality of your coating. Any contamination on the surface can result in the coating reticulating, a phenomena where the epoxy beads together and creates dry spots.
For superior clear coatings, sanding with the grain will enhance the aesthetics of the finished part. Naturally oily woods such as teak should have the surface oiliness removed with acetone and paper towels.
The working environment can play a large part in the quality of the finished coating and a dry dust free environment will obviously give better results. Importantly the temperature of the workplace, the temperature of the wood and the temperature of the epoxy should all be similar. 18°C would be a comfortable working temperature.
It would be a big mistake to apply cold epoxy onto a wood surface that is being heated as this would cause the air in the wood fibre to expand. This is known as ‘outgassing’ and can cause air bubbles to be trapped in the coating, or ‘cratering’ and ‘pitting’ as the bubbles leave the surface.
Epoxy that is cold, or becomes cold when meeting a cold surface, will be difficult to brush or roll out and will be applied too thickly, which can result in an uneven coating.
Applying the epoxy
Once your surface is fully prepared, you can start applying the epoxy. It is advisable to apply multiple thin coats rather than a single, thick coat. best results are achieved by applying the epoxy evenly. The ‘roll on and tip off’ method is a great way to do this – ‘roll on’ a thin layer of epoxy with a foam roller and then ‘tip off’ by dragging another roller, cut into sections, across it to leave the surface both level and free from air bubbles. The yellow WEST SYSTEM® 800 (7” ) roller sleeves are superb for this application.
With some coarse grain timbers the first coat may be quite rough and lift some wood fibre from the surface. If this happens then stop, allow the coating to cure and then sand the surface until it is smooth ready for the next coating application.
Once the epoxy is as tacky as masking tape, apply the next coat. If you can’t make a fingernail impression in the coating, wait until that coat has cured and then wash any amine blush away before abrading the surface ready for the next coat. Whilst the epoxy cures, gently apply a dry heat source, such as a hot air blower (or propane torch used with extreme care), to remove any air bubbles. Warming the epoxy will reduce the viscosity, thus enabling the air to escape more easily.
For the best results:
- Prepare surfaces scrupulously – make sure your surface is dry, free of dust and other contaminants, and thoroughly abraded.
- Use WEST SYSTEM 207 Special Coating Hardener® . This will cure with limited blush in a good environment. Also the mixed epoxy flows out beautifully as the viscosity is ideal for clear coating.
- Apply multiple thin coats using a foam roller and tip off the surface after each coat. You will typically need 2-4 coats, ideally applied once the previous coat becomes tacky.
- If you are coating a surface that will be used outdoors, it’s important to apply a UV resistant clear coating over the epoxy. Whilst the WEST SYSTEM 207 Special Coating Hardener contains a good UV inhibitor, you will still need an additional UV resistant coat to protect the epoxy from the eroding effects of sunlight.
If followed correctly, you should end up with a smooth, aesthetically pleasing clear coating that you can be proud of – bubble and blister free.
For more information on using epoxy to get a perfect coating, click here.