Marine Epoxy Mixing Ratios: Volume vs Mass and Gram Targets
Understand manufacturer-specified volume and mass ratios, scale marine epoxy volume batches, and use density-derived gram targets without confusing the two ratio bases.
Volume ratios and mass ratios are different
Follow the ratio basis stated for the exact epoxy system. A product may specify a ratio by volume, a separate ratio by mass, or both. Because resin and hardener densities can differ, a numerical ratio such as 5:1 must not be assumed to mean the same thing on a measuring cup and on a scale.
MixByParts currently scales ratios by volume. It can convert each calculated volume into an optional gram target when you enter exact component densities, but that conversion does not replace a manufacturer-specified mass ratio. Read the density and gram-target guide for the calculation limits.
Quick math checkpoint
For a manufacturer-specified 5:1 ratio by volume, a 946 mL batch contains approximately 788 mL resin and 158 mL hardener. Only convert those amounts to grams using densities published for those exact components.
By-volume marine epoxy tables
Use these tables only when the exact product specifies the displayed ratio by volume. Each card links to the interactive epoxy calculator so you can change the final volume or enter exact densities for optional gram targets.
5:1 marine laminating
Ratio basis: volume
| Total batch | Resin (mL) | Hardener (mL) |
|---|---|---|
| 32 fl oz (946 mL) | 788 mL | 158 mL |
| 1 gallon (3,785 mL) | 3,154 mL | 631 mL |
| 5 liters | 4,167 mL | 833 mL |
3:1 casting & structural
Ratio basis: volume
| Total batch | Resin (mL) | Hardener (mL) |
|---|---|---|
| 750 mL batch | 563 mL | 187 mL |
| 2 liters | 1,500 mL | 500 mL |
| 4 liters | 3,000 mL | 1,000 mL |
2:1 adhesives & fillers
Ratio basis: volume
| Total batch | Resin (mL) | Hardener (mL) |
|---|---|---|
| 500 mL batch | 333 mL | 167 mL |
| 1 liter | 667 mL | 333 mL |
| 2 liters | 1,333 mL | 667 mL |
Product instructions override these mathematical examples. Confirm ratio basis, temperature limits, batch size, and application method before mixing.
Step-by-step mix workflow
Consistent batches are about rhythm. Use the checklist below every time you mix so your layups cure hard, fair, and bubble free.
1. Stage the workspace
Prepare the PPE, clean containers, measuring tools, timer, and application area required by the exact product instructions before opening either component.
2. Confirm ratio and basis
Confirm the exact resin-to-hardener ratio and whether it is specified by volume or by mass. These calculators scale volume ratios; use a manufacturer-provided mass ratio directly when the instructions are by mass.
3. Measure the components
Measure each component using the method specified by the manufacturer. Optional MixByParts gram targets are conversions of a volume result and require exact component densities.
4. Mix as directed
Follow the product’s stated mixing time, scraping method, induction time, working time, and transfer procedure. These requirements vary by system.
5. Respect batch and application limits
Stay within the manufacturer’s maximum batch size, temperature range, application thickness, and working-time limits. Recalculate smaller batches when necessary.
Ready to scale a manufacturer-specified volume ratio? Open the epoxy calculator hub and load presets for tabletop pours, laminating runs, or structural bonding before you tape off the hull.
Control exotherm and pot life
Epoxy reactions generate heat, and safe batch sizes vary by product and conditions. Follow the manufacturer’s limits and use the calculator to scale a confirmed volume ratio into smaller batches when directed.
Exotherm minimizers
- Pour into wide, shallow trays immediately after mixing to bleed heat.
- Run fans across the layup or mold to exchange air and slow the reaction.
- Switch to slow hardener when the job stretches beyond the posted pot life.
- Stack multiple smaller batches instead of doubling a single mix beyond spec.
Batch sizing for repairs & fairing
Hull repairs, fillets, and fairing work reward small, precise batches. Use the 2:1 and 3:1 tables above as a launch pad, then adjust totals down to 150–250 mL inside the calculator for microballoon or cabosil mixes. Save each preset so repeat repairs on the same vessel take seconds to plan.
Working on brightwork or teak encapsulation? Pair these ratios with a final foam cannon rinse to strip salts and sanding dust before you lay down epoxy or varnish.
Cleanup & disposal
Wipe uncured resin with denatured alcohol, acetone, or manufacturer-approved solvents. Let cups cure before tossing them; most docks require fully hardened waste in the bin. For brushes, work solvent through the bristles, wash with warm soapy water, and hang to dry.
Label everything
Use painter’s tape or printable labels with the ratio, ratio basis, measured amounts, and timestamp. That way, the next batch does not rely on memory.
FAQs
Can I mix marine epoxy by volume?
Yes, when the exact product specifies a ratio by volume. If it instead specifies a ratio by mass, use that mass ratio directly. Do not assume the same numerical ratio applies to both bases.
How do I avoid exotherm in big pours?
Keep batches under the manufacturer’s recommended max, spread them thin, and use slow hardener when working in warm weather. Reuse the calculator to queue up identical follow-up pours instead of doubling a single batch.
What if the SDS density is missing?
Use the measuring basis specified by the manufacturer or ask for the exact density. Without reliable component densities, measure a by-volume recipe by volume and do not rely on estimated gram targets.