Sometimes an epoxy topcoat will develop an unwanted yellow hue. This is a problem that can affect epoxies regardless of whether it is a clear system or not and will typically be because of one of the following reasons:
Causes of Yellowing in Resin Floors
- Direct sunlight is usually the most common cause of a floor yellowing and losing its gloss, as the yellowing process is accelerated by exposure to UV light.
- Using resin flooring material that is past its expiration date.
- Improper storage of the product. Resins and hardeners need to be stored in a cool, dry place away from sunlight and with a stable temperature.
- Epoxy yellows after curing when exposed to water, moisture, excessive heat or the sun.
Once yellowing has occurred it is very difficult to repair and in most cases the floor area will need to be completely recoated.
Preventing Yellowing in Resin Floors
Consider putting down a clear, UV resistant and non-yellowing sealer over the epoxy floor, as this will make it much easier to clean, will resist stains and will protect against fading and discoloration.
Often epoxies are top-coated with a clear aliphatic (non-yellowing) urethane sealer, which is a two-part polymer that hardens just like epoxy and when used as a sealer will help to retain the epoxy floor’s colour and attractive gloss.
One other way to minimise the impact of yellowing is to select pigmented epoxy colours that are dark or that contain a lot of yellow (such as green) to begin with.
Causes of Cloudiness in Resin Floors
One other undesirable type of discoloration is when an epoxy coating appears white or cloudy immediately after installation or curing.
This is usually caused by the resin floor being exposed to water prior to it completly curing. Moisture in the concrete substrate or high levels of humidity can both result in sufficient amounts of water being present to affect a resin finish in this way. This can result in a “milky” or “greasy” film, which is sometimes referred to as a “blush” or “amine blush”.
A milky or cloudy appearance can also be the result of the product being applied too thick and will be more noticeable if the coating is clear.
Preventing Cloudiness in Resin Floors
It’s important to monitor the moisture levels in the substrate as well as the humidity levels before applying a coating. Be sure to check the Product Data Sheet for the system in question to find out the maximum amount of relative humidity (RH) that can be present in the substrate as well as the recommended material thickness.
If cloudiness does occur it may be possible to repair the affected area by diamond grinding the compromised coating, reapplying according to the Product Data Sheet’s recommendations and if the surface appears greasy wipe it with Denatured Alcohol.