River table leaks and blowouts

A leak in a river table form is expensive twice: you lose resin you paid for, and the pour level drops while the resin is still liquid. EcoPoxy’s river table tutorial puts it plainly: make the form level and as leak-proof as you can, because the last thing you want is a blowout (EcoPoxy).

Why deep pours leak more than coatings

Deep-pour resins are made thin. TotalBoat describes them as having a thinner viscosity for easy flow and a working time of up to 4 to 6 hours (TotalBoat). Thin resin finds gaps a coating resin would bridge, and a long working time gives it hours to drain through them.

Where leaks start

1. Inside corners and seams where walls meet the base.
2. Tape that is not fully bonded, with wrinkles or lifted edges that open a channel.
3. Screw holes and gaps around clamps that pass through the form.
4. Low walls or a tilted form, where resin rises above the wall on one side.

How manufacturers build a leak-proof form

• Line every surface. EcoPoxy covers all mold cavity surfaces with mold release tape or sheathing tape, completely flat and sealed to the mold surface (EcoPoxy).
• Seal the seams. EcoPoxy applies a bead of silicone along all inner joints, smoothed like caulking a bathtub, and waits for it to set; for a first project it adds a fillet of silicone along the outer edges too (EcoPoxy). TotalBoat’s kit advice is plastic tape inside the box plus silicone or marine sealant along all seams and joints (TotalBoat).
• Taller walls. EcoPoxy makes the sides at least 1/2 in taller than the slab thickness to avoid overflow (EcoPoxy).
• A wider base. Extending the base beyond the walls lets you see the seams during the pour, in case a leak needs patching (EcoPoxy).
• Level, and a catch sheet. EcoPoxy levels the form and suggests a polyethylene sheet under it to catch any leak (EcoPoxy).

TotalBoat’s river table materials list includes melamine board, packing tape, a hot glue gun and silicone sealant for the form (TotalBoat). The mold release and leak-proofing guide covers materials in more detail.

Before the real pour

• Let the sealant set for the time its maker gives before any resin goes in.
• Inspect under a light, especially the inside corners.
• Pour the first layer thinner if the product allows it, and watch the seams from the side and underneath.

If it leaks during the pour

Stop pouring and find the leak; the wide base and the catch sheet make this easier. Whether a seam can be patched with fast-setting material while the resin is liquid depends on where it is and how fast it is flowing. Keep enough mixed resin in reserve to top up the level, which is one reason to include a margin in your river table volume.