Epoxy problems – Improper mixing resulting in tacky, uncured spots.
One of the main problems people have when starting in the wonderful world of epoxy is that they end up with a spot on their project that doesn’t cure fully and feels tacky. This is usually a spot about the size of a dime and is almost always some unmodified resin due to a mixing issue.
Mixing epoxy is as easy as blending the prescribed amounts of A and B together thoroughly. Mixing is one of the most misunderstood parts of working with epoxy. Here are some myths regarding epoxy and mixing.
1. You need to mix the epoxy for several minutes. FALSE. Epoxy should be mixed thoroughly but if warmed to a temperature around 80 degrees it should take seconds, not minutes, to blend thoroughly.
2. You need to transfer the mixed epoxy to different containers and mix again. FALSE. Epoxy can be mixed and used from your primary container.
3. You need to wait some amount of time to use epoxy after mixing. FALSE. Epoxy does not need to sit in a container for any length of time after mixed thoroughly, it can be used immediately.
4. You need to worry about whipping air into epoxy when mixing, so stir slowly and don’t use a drill attachment. FALSE. Common sense and good safe stirring won’t create issues. If you see bubbles in your stirred mix, most will go away on application. Epoxy is generally high in viscosity at lower temperatures and becomes increasingly hard to mix the cooler it gets. To avoid mixing issues warm your epoxy to at least 75 degrees. Many people prefer it several degrees higher.
These misconceptions about epoxy mixing are wrong and actually can create significantly shortened pot life. Epoxy starts its chemical reaction as soon as A is mixed with B. Taking time to mix or let it settle will decrease the time it can be manipulated and applied successfully. You can also end up with over cured and wasted product that you can’t apply to your job.
Repairing These Uncured Mistakes
Now, if you made a mistake and need to repair or repour it is essential to remove all soft spots of uncured epoxy as it is not a stable base for the new epoxy to stick to and can create additional problems. There are several solvents including denatured alcohol, acetone, and xylene that will remove tack spots. It is best to get a cloth that won’t shed and place it over the affected area. Depending on the depth of the pour it may take a few minutes to soften; this can be accelerated by scrubbing it with steel wool. After it is softened take a microfiber or shed free cloth and wipe. When it is dry, check to make sure all tacky spots have been removed. Do not use flammable solvents in areas with lit pilot lights or any kind of open flame.
Once everything is dry, free of tacky spots, and cleaned you can decide the extent of the repair needed. Sometimes you can make a spot repair in areas that are less noticeable. The trick to making a spot repair is to get the epoxy to the exact height as the material around it. You can add or remove small amounts of epoxy with a pencil or screwdriver, lightly torch the area and check the level compared to the remaining areas. Sometimes you may have a spot that is bigger and will require repouring the entire area. If it has been 48 hours or less you should be able to get by without sanding. If it has been longer it will be advisable to lightly sand your surface with 400 grit sandpaper and clean with Windex. Use your hand to check for any bits of sanded epoxy on the surface.
Follow this guide and you should be happy with your results. Grab some sample boards and practice fixes so when you get in the heat of a job, you will handle it like an iCoat Pro.