Troubleshooting Application Problems

  • Fish Eyes: They occur due to a difference in surface tension between the coating and the substrate. This can be the result of a contaminant (oil, grease, dust, sealers, etc.), amine blush, primer outside the recoat window, moisture, etc. In most cases good surface preparation will solve the problem. To verify if the problem is substrate or product related, mix a small amount of the material and apply to a sealed surface outside of the project environment. If this does not fish eye , you know the problem is on the substrate. If this also fish eyes , stop coating and call Technical Service. you can add more mesh silica flour, to stop fish eyes . The silica flour can only be mixed in (dispersed) with a drill mixer. This can slightly change the color so be consistent. This is not a substitute for proper surface preparation.Do not add silica flour into a clear epoxy topcoat as it will cloud or opaque the coating

  • Air Bubbles: These can result from a variety of factors. Typically, if the problem is in the material, bubbles will occur uniformly and within 30 minutes of application. This can be the result of the product, temperature, mixing or application technique. When coating an excess broadcast floor, the bubbles are often the result of trapped air in the texture that expands as the day heats up. Make sure you are not whipping air in during mixing. Keep the roller fully wet out. Sometimes you can break the bubbles by re rolling after the material has set for 30 45 minutes. This is temperature dependent as you can also change the texture if the material is too far along in cure. A porcupine (spiked) roller can also be helpful to break air bubbles if they are fairly large and not extensive. This must be done soon after placement. Do not use if the material has any tack or you can leave small dots of a different color shade. Check substrate and product temperature. The thicker the film and lower the temperature, the more difficult it is for the resin to release air. The addition of silica flour, as mentioned above for fish eyes, will stop air bubbles if they are product or mixing related. Have an air release additive on hand for all coating application, as a precaution. Contact General Polymers for a recommendation. Substrate out gassing is difficult to predict or anticipate. Priming or coating late in the day, as the slab temperature is falling, is a good practice. These bubbles occur late in the cure, often after the contractor has gone. The product is no longer fluid and will not flow back to close the hole. They appear as small craters, with raised edges. To repair they must be sanded smooth and the hole filled prior to coating, or they will reappear

  • Amine Blush: This phenomenon is common. The name refers to the curing agent/hardener, which is an amine. It can and will react with moisture and carbon dioxide in the air to form the blush. Dependent upon the formulation, it is most likely to occur at low temperatures or high humidity and is worse when in combination. Many novolac epoxies will blush in ideal conditions. The blush should be visible as a film or haze on the surface that reduces gloss. It is noticeable by touch. It can be removed by a warm water detergent scrub, solvent or mechanical abrasion (sanding). A blush can also be an indication of improper mix ratio or an incomplete mixing. The Part B is less than the Part A and will come to the surface if in excess or not properly mixed

  • Color Change/Pigment Float: Epoxies by chemistry are not color stable. If you do a project in phases, with the same batch # of material,you can anticipate a slight shade differential at the tie in. Use only one batch # of topcoat, if you have more than one batch #, box the material. As discussed earlier an epoxy coating is a chemical reaction. It typically takes hours to reach completion. The pigment(s) are solid particles in suspension within a film that is cross linking. This is why you can touch an epoxy well into cure and the color can change,typically lighter, as you disrupt the process. Plan your project to minimize the time between mix to mix tie ins. This is formulation and temperature dependent but a good rule is: try not to go beyond 20 minutes. Do not roll into a partially cured edge. Use joints or other natural breaks to minimize the time between mixes. If you cut in too far out in front, you will need to re roll over this material to avoid a shade differential. Special color requests are more likely to have a pigment flotation issue than standard colors. It can be more pronounced in dark/deep blues, browns and greens.


Written by Mr.V.S. Anandha Kumar (Technical Head - ASTRA)