Installation of 100% Solids Epoxy Floor Coatings

It would seem the installation of a coating should be relatively simple and straightforward. The removal of solvent from epoxy floor coatings has certainly been good for the environment and safety concerns, but it has made a successful installation more difficult to achieve. A good solvent package aided the formulator and installer in a variety of ways; air release, surface tension (fish eyes), viscosity, pot life and pigmentation to name a few.

In an effort to assist in the installation process please review the items below prior to starting a project.

Surface Preparation: Vacuum, steel shot, blasting is by far the preferred method of surface prep. A profile of CSP 2 or 3 is recommended as detailed by ICRI. If this is not familiar, the profile should appear similar to 60-80 grit sand paper. To hide this profile it will require a minimum of 15 mils of finished coating thickness. For best results use a fill coat of epoxy to hide the profile prior to applying the topcoat. Any substrate imperfection, cracks, divots, spalls, pop-outs, over lap of blast pattern, etc. will show through. All imperfections should be pre-filled prior to coating.

Acid etching is often used for surface prep as many coating specifications are less than 15 mils total thickness. As mentioned above you will not often be able to hide a shot blast profile with 15 or less mils of coating. Acid etching is not preferred as it can be inconsistent in profile, introduces water into a porous substrate, and a byproduct of the acid base (concrete) reaction is the formation of salts. If these salts are not removed with the rinse water they will dry on the surface and inhibit long-term bond. If acid etching is the only viable option, refer to ASTM D4260 (good) or ICRI Guideline 03732 (best) for details

Joints and Cracks: Honor all expansion/isolation joints (do not coat). Fill with the appropriate joint material, flexible or semi-rigid, after installation of the coating. Saw cuts, cracks or control joints can be filled and coated over in a temperature controlled environment. For proper procedures/techniques and products visit our website or contact your General Polymers representative.

Temperature: 100% solids epoxies are dramatically influenced by temperature. Working time, cure time, viscosity (mixing & flow), air release, surface tension and pigment float will all be affected. These products work best at 70-85 degrees F in a combination of surface, product and air temperature. Outside of this range care will need to be taken to insure success. As an example: A 15 degree change in resin temperature (from 70 to 55) will more than double the viscosity of the product. The resin will still cure at 55 F but mixing, flow, air release, and pigment float will all be negatively impacted. Know your temperatures before you start, buy an infrared thermometer for each crew. A product temperature of 70 is ideal, but if placed on a 45-degree substrate it will not flow, release air or cure as hoped.

Dew Point: Dew point is the temperature at which moisture is converted from a gas to a liquid. Moisture will condense on a cool surface if the temperature is at or below the dew point. Yes, this can occur on an interior slab if the building temperature/environment is not controlled. It is difficult to impossible to see moisture on an absorbent surface like concrete. The moisture present can be enough to inhibit bond. To eliminate this potential check the dew point. Do not coat if you are within 5 degrees of the Dew Point. If this is not possible leave a fan running overnight in the room to be coated. Have you ever seen dew on a windy morning?

Moisture Vapor Transmission: Coatings are the most likely impermeable resinous floor system to fail when excessive Vapor Transmission rates are present. Use Calcium Chloride Test Kits to verify prior to coating. If readings are above the acceptable limits contact General Polymers Technical Service Department. If you are not familiar with Calcium Chloride Test Kits, how to use them and what they mean contact your General Polymers Representative or the Technical Service Department.

Mixing: Match your drill speed and paddle to the volume to be mixed. The spiral type paddle works very well with coatings. Avoid a vortex due to paddle size or drill speed; this will whip air into the coating. Do not "pump" the paddle up and down. Quantities less than a gallon can be mixed by hand. In pigmented systems, and as a general practice, it is a good idea to measure off the Part B (curing agent/hardener) and put into the mixing container first. These materials are typically lower in viscosity and weight per gallon than the Part A. They are very good wetting agents. As you add Part A it will displace the Part B, which will come to the top, coating the bottom and sides. The drill and paddle will now not have to remove the sticky Part A from the sides and bottom of the bucket.

Mix no more than can be applied in 30 minutes. Do not let mixed material sit in volume. Once mixed, dump the entire quantity on the floor. When you mix an epoxy you start a chemical reaction that is accelerated in mass. Product left in the bucket for several minutes will be at a different stage of cure than material first placed. This can affect flow, texture, air release and pigment float. The higher the viscosity of the material being mixed the longer you mix. For an epoxy to cure fully each molecule of hardener must find the appropriate molecule(s) of epoxy resin to react. As more and more connections occur the remaining molecules have more difficulty finding each other.

Priming: Yes, you should. Good primers penetrate the substrate and provide a good bond site for the next application. They also reduce concrete out-gassing and provide some film build to reduce surface profile. Match your primer to the coating system. Most manufacturers make several primers for different conditions: low temperature, oily substrates, solvent or 100% solids, blush resistant, etc. Check with Technical Service for a recommendation if in doubt. As a general rule use the fastest curing, low viscosity primer available. This combination works best to reduce out-gassing from the substrate.

Application: As a general guideline, do not exceed 20 mils of "neat" resin, per lift, without the use of a filler. Thick films will be more brittle and have a tendency to hold more air bubbles. There are exceptions to this so review the data sheet of the product to be used. Most formulations work best at 8-12 mils. Without exception the best results will come from applying the product with a flat squeegee and back rolling with a high quality short nap roller. A squeegee distributes the material evenly and is the most efficient in terms of time. It also insures the entire mix is curing at the same rate. If you cannot use a squeegee, pour the entire mix in a ribbon and roll in and out of the ribbon. Keep the roller fully wet out (saturated). As a roller empties it fills with air, which will now be put into the coating. Dip and rolling out of a bucket may work occasionally but it is not a good practice. Purchase spiked shoes and learn to use a squeegee.

Recoat Window: Follow the guidelines listed on the Technical Data Sheet for the primer, fill resin or topcoat as the case may be. Recoat windows will be impacted by temperature. A recoat window of 24 hours, at 70F, will be reduced by several hours if installation temperatures were above 80F. If in doubt, or you are at or beyond the recoat window, sand prior to coating. Do not recoat a solvent-based primer until the solvent has evaporated. If you touch the primer and your finger has any residue on it, wait. You can coat a 100% solids epoxy with another 100% solids epoxy, prior to full cure, without fear of one, the other, or both not curing. The question is, do you want to do this. If the resin is not cured enough to support traffic, you will leave footprints or cleat marks. You could also mix partially cured material into the new material when back rolling. You may want to do this when using a fill/body coat over a 100% solids primer. The body coat should have enough mil thickness to cover any cleat marks.

Trouble Shooting

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 1-2 pounds of 325 mesh silica flour, per mixed gallon of pigmented epoxy, 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 applications, 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 dense 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. This is a one time formula with which we have no history or experience.

Specialty Tools

  • Spiked shoes - Those back rolling will need to walk in wet material.
  • Silica flour- GP product number 5350
  • Loop rollers- For self-leveling coating applications of more than 12-15 mils. They leave no roller fuzz nor do they impart air. If utilized in a thin film, they will leave texture
  • Porcupine rollers- To remove air bubbles, while the material is still wet
  • Mil gauges- To insure thickness and coverage rates
  • Infrared Thermometer- Do not leave home without it
  • Dew Point/Humidity Meter (Psychrometer)
  • Air Release Additive
  • Adhesive roller covers are great to back roll with but can be hard to find. Some Home Depot and Sherwin-Williams stores do carry them. They shed almost no roller fuzz/lint. They should only be used to back roll as they hold little material and must be kept full to avoid whipping air into the coating.