Mixing Epoxy Correctly
Epoxy adhesives cure through a chemical reaction between two components: a resin and a hardener. Manufacturers specify a ratio—commonly written as 2:1 or 5:1—that must be followed precisely for the mixture to reach full strength. Too much hardener leaves brittle cured epoxy, while too much resin causes slow or incomplete curing. Our calculator translates the ratio and total desired quantity into exact portions for each component so you can measure confidently.
How the Formula Works
Suppose your epoxy calls for a resin-to-hardener ratio of . If you need grams of mixed epoxy, the amount of resin is . The hardener is . These fractions ensure the parts add up exactly to . The script applies this formula when you submit the form, displaying results instantly.
Units and Precision
You can select grams or milliliters depending on whether you prefer weight or volume. Most epoxies mix by weight for accuracy, but some small hobby kits list ratios by volume. If you weigh your components, use a scale capable of grams or fractions thereof. For volumes, consider using graduated mixing cups or syringes. Precision is critical, especially for small batches like jewelry casting or model building where small errors make a big difference.
Example Calculation
Imagine you need 150 grams of epoxy with a 2:1 ratio. Enter "2" for the ratio and "150" for the total amount. The calculator outputs 100 grams of resin and 50 grams of hardener. This ensures the correct stoichiometry for the curing reaction. If you change the ratio to 3:1 for the same total amount, the resin portion becomes 112.5 grams and the hardener 37.5 grams.
Typical Ratios and Properties
| Ratio (Resin:Hardener) | Common Usage |
|---|---|
| 1:1 | Fast-setting craft adhesives |
| 2:1 | General purpose laminating resins |
| 5:1 | Marine-grade structural epoxies |
Mixing Tips
Thorough mixing is vital. Scrape the sides and bottom of your container to ensure all resin and hardener meet. Mix slowly to avoid introducing bubbles. In cool weather, slightly warming the resin can reduce viscosity, but never use open flames. If your pot life—the time before the mixture begins to gel—is short, gather all tools beforehand so you can apply the epoxy immediately after mixing.
Allowing for Application Loss
Projects often require a little more epoxy than calculations suggest because some material clings to mixing cups or tools. The optional allowance field increases the total amount by the specified percentage, giving you a buffer to account for drips or absorption into porous surfaces. For example, a 5% allowance on a 100 gram batch prepares 105 grams of mixture.
Handling Exotherm
Large batches of epoxy can become hot due to the exothermic reaction between resin and hardener. To control this heat, mix only what you need and spread the epoxy thin once mixed. If a container begins to smoke or warp, move it outdoors or submerge it in sand to dissipate heat safely. Following recommended ratios minimizes runaway reactions and ensures a consistent cure.
Temperature and Cure Time
Ambient temperature influences how quickly epoxy hardens. Warmer rooms accelerate curing while cold spaces slow it down and can leave the surface tacky. Manufacturers often specify an ideal range—commonly 20–25 °C. If working in cooler conditions, consider using a space heater to maintain temperature or choose a formulation designed for low-temperature curing.
Volume vs. Weight Considerations
Some systems provide ratios by volume but differ in density between resin and hardener. When accuracy matters, weigh the components instead of measuring by volume or consult the product’s datasheet for specific gravity values. Accurate conversions ensure that the chemical reaction proceeds as intended.
Limitations
This calculator assumes you have a single simple ratio and that resin and hardener densities are similar if you measure by volume. Some specialized systems require accelerators or fillers that change the effective ratio. Always consult the manufacturer’s instructions for complex mixes. When in doubt, test a small batch first to verify the cure.
Cleanup and Safety
Wear gloves and eye protection when handling uncured epoxy. Spills can be cleaned with isopropyl alcohol or vinegar before the resin sets. Proper ventilation minimizes inhalation of fumes. After curing, most epoxies are inert, but uncured components may cause skin irritation or allergic reactions.
Conclusion
Accurate mixing leads to strong, durable epoxy bonds. By entering your ratio and total amount, this calculator eliminates guesswork, letting you focus on the creative or structural aspects of your project. Because the script runs entirely in your browser, your measurements remain private. Take a moment to double-check your units and enjoy the reliability of a well-mixed adhesive. The copy button allows you to save calculations alongside project notes for future reference.