Mixing epoxy by weight vs volume

The ratio includes a measuring method

An epoxy ratio is incomplete without knowing whether it describes weight or volume. Resin and hardener can have different densities, so equal volumes need not weigh the same. Use the exact ratio published for the product and the method you intend to use. Never transfer a volume ratio directly to a scale unless the manufacturer explicitly gives the same ratio by weight.

TotalBoat’s current TableTop documentation illustrates the distinction: its volume ratio is 1:1, while its weight ratio is 120 parts resin to 100 parts hardener. Those numbers belong to that product. Another resin, or a different hardener within a product family, may require different proportions.

Calculate the batch before opening bottles

For a published ratio A:B and a chosen total in the same measuring basis, the resin amount is total multiplied by A divided by A+B. The hardener amount is total multiplied by B divided by A+B. Keep the units consistent. A total mass target produces component masses; a total volume target produces component volumes.

As an arithmetic example using the TableTop weight ratio above, a 220 g mixed batch uses 120 g resin and 100 g hardener. A 110 g batch uses 60 g and 50 g. These examples explain scaling the published ratio; they do not recommend a batch size for every project or container.

Compare a relevant resin kit

TotalBoat TableTop: check the selected 1 gallon kit, included components and current offer. Read the formula limits before choosing it for your project.

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Read formula notes and other kit sizes

Choose tools that can resolve the small component

A scale is useful only when its capacity, resolution and repeatability suit the batch. Evaluate the smallest component addition, not just the total. If a display changes in large steps compared with the amount of hardener required, choose a suitable scale or a manufacturer-approved alternative. Do not round quantities until the ratio becomes convenient.

For volume measurement, use a suitable graduated container and read the marks consistently on a level surface. Do not estimate equal amounts from different-shaped cups. Calibrated dispensing pumps are another option when they are matched to the exact system and used according to their instructions; equal pump counts do not mean equal component volumes.

Use a written dispensing sequence

Place the cup on a stable surface, confirm units and note whether you will tare between additions. If you tare, the second target is the hardener quantity alone. If you do not tare, the final display target is the combined mass. Write both targets before starting so you do not switch methods halfway through.

Keep the component containers and lids clearly identified. If an addition overshoots, stop and recalculate only when the actual dispensed quantities are known and the manufacturer’s process allows correction before mixing. Do not remove an arbitrary spoonful of combined liquid and assume the ratio is restored.

• Check the exact product and hardener names.
• Copy the ratio and label it by weight or by volume.
• Calculate each component and verify the total.
• Confirm tool units, tare procedure and measurement range.
• Mix using the product’s stated time and scraping method.

Mixing completes what measuring starts

Accurate quantities still need thorough blending. Reach the cup bottom, sides and corners as directed. If the instructions call for transferring to a second cup and mixing again, include that time in the working period. Do not apply a generic mixing duration from another brand or deliberately shorten it to avoid introducing air.

Add pigments or fillers at the stage and loading permitted by the manufacturer. Changing the resin-to-hardener ratio is not a cure-speed adjustment. Keep a batch note with the actual quantities, measuring basis and conditions; if a defect appears later, those details turn a vague failure into a problem you can investigate.