Amine blush, bloom, or “sweating” are common names used to identify the greasy or whitish deposits that form on the surface of epoxy when environmental conditions such as cool temperatures, elevated levels of carbon dioxide, or elevated moisture levels are present. Save yourself from going red in the face with embarrassment by preventing amine blush before it happens.
A very simplified version of the chemical reactions that produce amine blush (ammonium carbamate) is provided below for illustration:
How to Prevent an Amine Blush?
The best way to prevent an amine blush is to monitor and control the environmental conditions. Only apply epoxy when the air and surface temperatures will remain within the recommended 60°F to 85°F, and avoid a condensation event by staying at least 5°F above the dew point throughout the application and cure. The storage of the hardener and resin within the same recommended temperature range of 60°F to 85°F prior to use is also recommended.
Because the formation of an amine blush requires carbon dioxide and water, eliminating significant sources of carbon dioxide and moisture vapor such as direct-fired heaters, engine exhaust, and other combustion processes are important factors to consider. All direct-fired heaters, including natural gas and propane units, produce carbon dioxide and water vapor as the fuel burns to generate heat. In an enclosed area, the carbon dioxide and water vapor produced by direct-fired heat can contribute to the formation of amine blush – especially near the heater. In addition, heaters that use fuels such as kerosene or fuel oil are not recommended because they also produce soot that will deposit on floor surfaces and become a bond breaking surface contaminate.
Let’s be honest, in most parts of the country the air is rarely at the optimal temperature range and artificial sources of heat are required not only for the comfort of the workers but to ensure a proper cure and bond to the substrate. Electric heat is the safest heating option during the application of epoxy as it does not produce additional carbon dioxide or moisture vapor.
Keep a close eye on the site conditions with the help of an all-in-one instrument that measures the relative humidity, substrate and air temperature as well as calculates the dew point and degrees above the dew point.
How to Detect an Amine Blush?
On some surfaces, such as some smooth epoxy surfaces it is sometimes possible to see or feel the amine blush as the epoxy will appear dull, hazy, or splotchy with a greasy/waxy feel. However, an amine blush on a lighter colored background or a grout coat over a broadcast of quartz or flake is virtually impossible to detect by sight or touch.
Field tests for amine blush based on pH have been used for years. However, pH-based tests can be misleading as amine blush is a salt and pH indication is susceptible to interference. A relatively easy field test that is selective to amine blush (carbamates) is the Elcometer 139 Amine Blush Test because the analysis is based on a reaction with a special enzyme and not pH. The results are indicated by a color change in the sample that is compared to the color of a control sample which is prepared at the same time. A sample that is less yellow in color than the control indicates the presence of amine blush on the epoxy surface.
How to Properly Remove an Amine Blush?
Because of the ionic nature of amine blush, the use of solvents to remove a blush is not very effective. However, the use of Dawn® dish soap in hot water following the Dur-A-Flex Cleaning Guidelines works well to remove and suspend the amine blush from the epoxy surface. Depending on the cleaning equipment available, it is recommended to repeat the cleaning process once or twice, prior to rinsing thoroughly with hot water, allowing the surface to dry before visual inspection and retest for amine blush.
Never use mechanical means alone to sand an amine blush off as this may result in spreading this bond breaker around. However, when dealing with coating delamination due to an amine blush, it is necessary to grind off the poorly bonded coating first and follow with the cleaning recommendations above.
Cleaning off an amine blush can be a challenge and typically may require more than one attempt. Be sure to verify the removal of the amine blush by re-testing the prepared surface prior to proceeding with a recoat. An Amine Blush is a significant bond inhibitor that must be completely removed prior to the application of the next coat in the floor system. Due to the time consuming and costly nature of removing an amine blush, best practice is to prevent it before it happens.