COATING EPOXY BASICS
Nerpa Coating Epoxy is formulated for use in projects like tabletop coatings, crafts, charcuterie boards, coasters and arts. It is a medium-high viscosity, self leveling, 24 hours curing time epoxy system. Here are basic notes to help you create a professional project.
1. Curing time
Pot life can be described as the time that it takes for the epoxy to double its viscosity after it was mixed. This parameter is essential for understanding the behaviour of the epoxy and planning your project ahead. For example, pot life of 55 min means that epoxy’s optimal air release properties will be maintained in the first 30-45 minutes after mixing. After passing the 55-minute mark, the reaction accelerates, and the viscosity increases rapidly.
Gel time provides information about how long it takes for 100g cylindrical shape casting to reach the gel state. Essentially, this information tells you the point when the speed of reaction and exotherm output for 100g casting reaches its maximum values. This parameter has more value for the relatively fast epoxies such as our Coating Epoxy as it provides additional data on the property of the epoxy system. For example, a 70-minute gel time allows having more working time and a smoother exotherm curve than a 40-minute gel time.
Set to touch
A time when you can touch the resin (in nitrile or rubber glove) with your finger without applying any pressure and not leaving an imprint on the surface is called “set to touch.” This information could help you get a sense of when the epoxy is already solidified to the extent that it no longer needs protection from the dust. If you are working with small projects like charcuterie boards and have access to industrial ovens, then set to touch time can be used as an indicator for the moment when you can shorten your wait time by applying post-curing techniques. Basically, at this stage you can heat your project up to 65°C for 3-5 hours. This will help epoxy cure faster but will not cause overheating as if you started heating your epoxy right after the mixing stage.
Dry through and ready for sanding
When epoxy reaches solid state throughout (80-85% from the full cure state), it is called “dry through”. It is not quite correct to call epoxy resin “dry” because it is not drying like paint but epoxy molecules reacting with each other, however the the term “dry through” became an industry standard and is widely used. Dried through material has reached solid state and is ready for sanding in case you want to apply a second coat of epoxy on top.
Full cure time
Full cure time for our Coating Epoxy is 7 days. Why do we specify 24 hours cure on our label, then? Nerpa Coating Epoxy resin cure kinetics follow the curve shown below:
90+% of the reaction happens in the first 24 hours followed by slow completion during the following days.
2. Mixing Part A and Part B
Limit the mixing time for 5-8 minutes. Use caution to avoid excessive air entrapment into the bulk of the mixture. Scrap the sides of the mixing container from time to time to ensure that homogeneous state is achieved.
3. Optimal working temperature
Coating Epoxy should be used in temperatures 22-27°C. Temperatures below 22°C are not ideal for Coating Epoxy because of the significant viscosity increase. You can use Coating Epoxy in low temperature conditions if you have a vacuum chamber to degas the mixed liquid.
4. Speed of cure and ambient temperature
A rule of thumb is that speed of reaction doubles for every 10°C increase in the temperature of Part A and Part B materials. If your epoxy was stored and then used in a warm place, then you can expect shortening of the available mixing and working times and higher probability of the overheating.
5. Coating epoxy use for small castings
1/16th to 1/10th of an inch (1.6 to 2.6 mm) coating thickness will not cause overheating of your epoxy. You can prepare any quantities of epoxy if this thickness range fits for your project. Just make sure to use all mixed resin within specified working time.
You can also exceed the above mentioned thickness if the volume of your pour is less than 80mL. Try to make a set of coasters with our Nerpa Polymers Coating Epoxy, Liquid Colourants and Pearlescent Colour Pigments!
6. Use of the torch
Experienced users know the trick of getting rid of air bubbles by using a propane torch. Combination of the heat and carbon dioxide from the bursts of flame immediately lowers the viscosity of epoxy and increases the surface tension of the bubbles. These two effects together efficiently force bubbles to pop. Only use the propane torch if you have previous experience. Do not use this method in spaces where flammable materials are present. Plan your actions ahead. Prepare a fire extinguisher in case of an emergency.
Depending on the type of your torch, short, 1-2-second-long bursts 10-20 cm away from the epoxy surface are optimal for maximum bubble disappearance.