TotalBoat Deep Pour Epoxy Review: Fathom vs ThickSet Explained

TotalBoat currently sells two clear casting epoxies that can be described as deep-pour products: Fathom Deep Pour and ThickSet Cast + Coat. They are not interchangeable. Fathom uses a 2:1 volume ratio and supports deeper, larger pours; ThickSet uses 1:1 and is intended for medium-depth work.

This is a research-based review. We have not purchased, mixed, poured, or tested either system. The conclusions come from TotalBoat’s current product pages, selection guide, and Fathom instruction sheet and technical data.

Quick Verdict

For the intent behind this legacy page, Fathom is the correct current focus. It is TotalBoat’s purpose-built option for large mixed volumes, river-table layers up to 2 inches, and smaller castings up to 3 inches. The 4-6 hour working time provides a long handling window, but the tradeoff is a slow 5-10 day full cure and strict attention to pour geometry and temperature.

Fathom is not the default choice for shallow coatings, small batches, or a modest 1/2-inch river channel. TotalBoat positions ThickSet for medium pours, while TableTop or another coating resin is more appropriate for thin flood coats. Choosing within the lineup by depth and volume is more important than choosing by brand name alone.

Does the Historical Product Mean ThickSet or Fathom?

The old article combined the words “ThickSet” and “Fathom” in one title while describing a 2:1 ratio, 2-3-inch layers, and a multi-hour working window. Those characteristics align more closely with the current Fathom system than current ThickSet.

Current TotalBoat documentation treats them as distinct products:

The legacy URL remains valuable and accurate at the category level, but the restored review corrects the old name conflation and evaluates the current Fathom product transparently.

Current Fathom Specifications

These limits work together. “Up to 3 inches” does not mean that any table-size mold can be filled 3 inches deep. TotalBoat limits larger slabs and river tables to 2 inches per layer and ties the 3-inch allowance to smaller castings and mixed volume.

Intended Applications

Fathom is documented for:

• River tables and live-edge slab pours
• Large casting molds
• Sculptures and encapsulation
• Deep channels and thick decorative castings
• Clear or epoxy-compatible tinted pours

It is not designed as a structural marine laminating resin merely because TotalBoat is a marine brand. It is also too slow for use as a porous-wood seal coat; TotalBoat recommends sealing porous surfaces with a suitable faster-curing epoxy before the deep pour.

Working Temperature and Exotherm

Fathom’s slow reaction makes deeper pours possible, but mixed epoxy still generates heat. TotalBoat specifies 60-80 degrees F as the broad working range and recommends around 70 degrees F for thicker pours. Warmer material and larger masses increase reaction speed and heat.

The instructions warn that an out-of-limits mass can reach very high internal temperatures and may yellow, crack, shrink, distort, or damage surrounding material. Pour-depth claims should therefore never be separated from mold dimensions, total volume, ambient temperature, and heat dissipation.

For layers beyond the applicable maximum, TotalBoat calls for step pours. The prior layer should be firm and cooled below 85 degrees F; the published guidance says to allow at least 36 hours before another Fathom layer.

Mixing and Application

Measure 2A:1B by volume or 100A:44B by weight without changing the ratio. TotalBoat instructs users to mix for 2-3 minutes while scraping the container, transfer to a clean container, and mix for another 2-3 minutes.

The minimum 1/2-gallon mixed quantity is easy to overlook. Fathom is deliberately designed around substantial pours, and tiny test amounts or very shallow layers may remain soft much longer than the headline cure time suggests.

Fathom is not compatible with TotalBoat’s ordinary 2:1 metering pumps. Large-volume measurement should follow the Fathom instructions rather than assuming that a pump sold for another 2:1 system meters the same ratio by stroke.

Strengths

Explicit Geometry-Based Pour Limits

TotalBoat distinguishes a large slab from a smaller casting instead of promoting one unrestricted maximum depth. That is useful planning information.

Long Working Time

A 4-6 hour work window can help with mixing a large batch, allowing bubbles to rise, placing inclusions, and managing a complex mold. It also signals that the product will be slow in thin or cool pours.

Strong First-Party Documentation

The current product page, comparison guide, support articles, and technical instructions answer many questions that marketplace-only resins leave open.

Multiple Large Kit Sizes

The 1.5-, 3-, and 6-gallon options fit the product’s large-volume purpose. Material calculations still need a waste allowance and should be completed before mixing.

Limitations

Poor Fit for Shallow Work

Fathom should generally not be used below 1 inch. A tabletop flood coat, seal coat, coaster, or small thin mold calls for a faster product designed for that geometry.

Long Cure Schedule

Full cure can take 5-10 days. Demolding too early risks deforming material that still feels soft or rubbery.

Temperature Control Matters

The deep-pour limit assumes suitable conditions. A warm shop, insulating mold, or oversized mass can change the cure dramatically.

UV Resistance Is Not Outdoor Immunity

TotalBoat describes Fathom as UV resistant but also recommends a UV-blocking finish for continuous outdoor exposure. That is a more realistic limitation than an absolute “will not yellow” promise.

Fathom or ThickSet?

Choose Fathom when the pour is roughly 1-2 inches across a river table or slab, or up to 3 inches in a qualifying smaller casting, and the project can tolerate the slow cure.

Choose ThickSet for medium-depth work: current guidance allows up to 1/2 inch on river/slab pours and up to 2 inches only in small castings using less than 10 oz. Its 1:1 ratio and faster 3-5 day full-cure schedule may be more practical for those smaller jobs.

Choose neither for a thin tabletop coating, routine fiberglass laminating, or structural bonding. TotalBoat has separate products for those intents.

Safety Considerations

Use the current Part A and Part B SDS, label, and Fathom instructions. TotalBoat calls for appropriate protective equipment and ventilation. CDC/NIOSH also warns that uncured epoxy components may be hazardous and that odor is not a reliable indicator of safety.

Avoid skin and eye contact, wear chemical-resistant gloves and eye protection suitable for the formulation, and keep the work zone ventilated. The exothermic hazard also means mixed resin should never be left in an unintended bulk container or poured beyond the documented limits.

Final Assessment

Fathom is a credible, well-documented choice for genuinely deep and large clear castings. Its 2:1 ratio, 4-6 hour work window, and geometry-specific 2- and 3-inch limits distinguish it from TotalBoat ThickSet. Those strengths come with a slow cure, a substantial minimum batch, and meaningful temperature and exotherm constraints.

The restored legacy review no longer treats ThickSet and Fathom as one product. For current buyers, Fathom is the relevant system when the project actually requires its depth and volume; smaller or shallower work belongs elsewhere in the lineup.

Sources

• TotalBoat Fathom product page - current specifications, kit sizes, intended uses, and limitations.
• Fathom instruction sheet and TDS - preparation, mixing, pour geometry, temperature, exotherm, layering, and safety guidance.
• TotalBoat epoxy comparison guide - current separation of Fathom, ThickSet, tabletop, and structural systems.
• TotalBoat ThickSet product page - current ThickSet ratio, uses, kit sizes, and pour-depth limits.
• CDC/NIOSH epoxy and resin guidance - general safety guidance for uncured epoxy systems.