EPOXY
Do not use epoxy by simply following the “text book”. It is critical to understand the basic chemistry and properties of the various chemicals. Some parts of the process are affected by various conditions during and after the building process. We will elaborate on how these factors may influence the build during the next couple of sections.
2.1. Epoxy Types
It is important to understand that there are hundreds of different types of epoxies available on the market. Each has different properties for different applications. Contact your epoxy supplier or manufacturer to ensure you buy the correct type of epoxy for your project.
Information such as mixing temperature and ratios, curing times, pouring thickness, etc. are critical to consider when planning your project.
2.2. Safety and Handling
Epoxy resin and hardeners are hazardous chemicals. This means that if they are handled or stored incorrectly, they can be dangerous to your health. Specific health and safety precautions apply when handling these chemicals. Please ask for a safety data sheet of the chemicals and familiarize yourself with their contents. Here are a few basic aspects of importance:
Ensure adequate ventilation. Simply hang a string on one of the doors or windows. The string will move in the same direction as the air is moving. This indicates ventilation of the workspace.
Use gloves and barrier creams to prevent skin contact with the chemicals.
Use safety glasses to prevent any droplets or wood shavings to enter your eyes.
Use skin-friendly hand soap to prevent skin irritation (redness, dryness, cracking, etc.). Never clean your hands using solvents.
2.3. Things to Avoid
Unprepared wood surfaces. To ensure effective bonding of the epoxy to the wood never apply epoxy on oily, damp, wet, or dusty surfaces.
Very humid or cold (below 18oC) working conditions. Your supplier or safety data sheet from the manufacturer should be able to provide information on working conditions that may impact the quality of your final epoxy product.
2.4. Storage and Stability
Again, refer to the safety data sheet. In general, epoxy has an average shelf-life of 24 months if you store it properly in a dry place, in original unopened containers, and at room temperature.
2.5. Epoxy Mixing
Make sure you mix the resin and hardener at the correct mixing ratios as prescribed by the manufacturer. These are weight ratios of the resin and hardener, not volume ratios.
Epoxies with a 1:2 mixing ratio can be mixed by volume.
It is therefore important to invest in a good and reliable scale or another weighing device if you are going to mix by weight.
For example.
The epoxy we are using is a 10:6 mixing ratio; meaning for every 10 parts resin we add 6 parts hardener.
Make sure you mix your resin and hardener thoroughly with something like a paddle stick for at least three (3) to five (5) minutes. The paddle stick must be long enough to reach the deepest corners of your mixing container. Ensure that all equipment and tools used are clean and free from dust and foreign particles.
2.6. Maximum Pour Depth or Thickness
There are two types of epoxy products for tables. A deep pour epoxy and multi-layer epoxy. The two factors to consider when choosing between the two are cost and time. Deep casting epoxy is much more expensive than multi-layer epoxy.
It is crucial to calculate and prepare the epoxy resin mix volume correctly as prescribed by the epoxy supplier or manufacturer. Keep in mind that the epoxy resin has an exothermic chemical reaction and if it is not poured in accordance with the prescribed method the final product may discolor, boil, crack or warp.
Be sure to add a sufficient amount of hardener to your resin when using epoxy. Adding too little hardener will cause the curing to take very long, or not cure at all.
TIP: The epoxy product we use can only be poured in stages and up to a thickness of twelve (12) mm.
Therefore, mark the sides of your mold to ensure you do not overpour.
Always remember deep casting and multi-layer epoxies are intended for the application they are manufactured for.
Deep casting epoxy can’t be used for multi-layer castings and multi-layer epoxies can’t be used to do deep castings. Ignoring this fact will end in disaster.
2.7. Curing Time
At DIY with Greg, we use multi-layer epoxy for various reasons we will explain later. Each layer must be allowed to cool down to room temperature before pouring the next layer. Depending on the working conditions in your workshop, you may be able to pour two (2) to three (3) layers per day. Use a thermometer to measure the previous epoxy pour’s temperature prior to pouring the next layer.
At DIY with Greg, we established to wait for at least four (4) to six (6) hours before pouring the next layer of epoxy. Drying is not purely a time-dependent factor but rather a factor of the drying capability of your work environment. It is HIGHLY recommended to obtain the recommended working conditions from your supplier. Casting in improper weather conditions may result in failure.
2.8. Color Consistency
There are 2 basic methods for achieving color consistency when pouring multiple epoxy layers.
The first method requires that you mix your color pigment into your main batch of resin only (AND NOT THE HARDER). Ensure proper mixing of the resin before your first pour.
The second method is to add the same volume of color pigment to each batch. This requires precise mixing ratios for every pour. Use a measuring spoon or syringe with clear markings. Add the exact color pigment volume of the first batch to each of the following batches; not necessarily the intended volume.
You will notice that with each layer you pour the color of the epoxy becomes darker. This is perfectly normal as less light is able to pass through the thicker layer of epoxy. How do we then determine the correct color of our final product?
Use a transparent container to prepare a sample. You may even build a small test mold. Mark the container, from the bottom, the same height as the thickness of your planned table. Pour epoxy to this level and let it dry to obtain a good indication of the final product color. The color pigment solution is extremely concentrated and should only be added in small amounts to the resin. For small batches, use a toothpick to add small amounts of pigments to the resin before adding the hardener. Be sure to stir the mixture well before making further color adjustments. A maximum of 2% to 3% by weight is normally sufficient.
There are also many different glitters, pearl essence powders, and color drops that can be used in your epoxy resins. It is advisable to experiment with a number of tests before applying to a big project.
2.9. UV Stability
Most epoxies are affected by UV radiation and therefore primarily intended for indoor use. Although many types of luminaires may emit UV radiation, it is far less intensive than sunlight. Please consult with your epoxy supplier and/or manufacturer to supply you with specialized epoxy if you are building a table for outdoor use. These generally contain polyurethanes which are much more expensive. Also ensure fully conversed with the health and safety measures when working with these types of epoxies.
Due to the likely change in color and reduced durability of the epoxy bond to the wood we are unlikely to agree to build a table that will receive direct sunlight.
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