How to Use Flex Seal Epoxy

Flex Seal® Epoxy is a high-performance epoxy designed for exceptional strength and long-lasting durability. Flex Seal Epoxy comes in a liquid form, dispensed in a syringe or two tubes, and a putty formula. Each format uses an advanced, multi-purpose formula that creates a permanent, watertight bond on a wide range of materials. Flex Seal Epoxy is the go-to solution for heavy-duty repairs, precision fixes, and everything in between.

From getting started to cleaning up, this article will show you how to use Flex Seal Epoxy safely and correctly for your projects and repairs.

Getting ready to use Flex Seal Epoxy.

How to properly apply Flex Seal Epoxy.

Using on wet surfaces or underwater.

How long does it take to dry?

What color is Flex Seal Epoxy?

Helpful hints and tips.

How to clean up Flex Seal Epoxy.

Storing and reusing.

Get Flex Seal Epoxy.

Getting Ready To Use Flex Seal Epoxy

Materials Needed:

• Protective gloves, clothing and eyewear
• Cloth/rag or Paper towels
• Plastic covering, drop cloth, or tarp

IMPORTANT: Before using Flex Seal Epoxy, read all directions carefully and take proper safety precautions, such as being in a well-ventilated area and wearing protective gear.

Protect areas you don’t want to get Flex Seal Epoxy on by protecting your work surface with a drop cloth or disposable covering.

To get the most out of Flex Seal Epoxy, READ THE DIRECTIONS CAREFULLY. Then, follow along with this blog for a comprehensive step-by-step guide.

How Do I Apply Flex Seal Epoxy?

Applying Flex Seal Epoxy — Extreme Liquid in a Syringe

1. Prepare Surfaces: Clean and dry application surfaces, removing any dirt, grease, or oil with a degreaser. Do not use alcohol or cleaners that may leave a petroleum residue. If the surface has rust, use sandpaper to remove.
2. Dispense & Mix: Remove the re-sealable no-waste cap from the syringe and save for later. Push the plunger to dispense equal amounts of resin and hardener onto the included plastic tray or a clean, disposable surface. Mix until fully blended and uniform in color (approx. 1 minute).
3. Apply & Join: Apply the mixed epoxy to one surface, press parts firmly together, and clamp if needed. Open work time is 45 minutes.
4. Cure: Allow Flex Seal Extreme Liquid Epoxy to cure undisturbed. It will set in 3–6 hours at room temperature and fully cure in 15–24 hours, or as fast as 1 hour with heat.

Can I Apply Flex Seal Epoxy on Wet Surfaces or Underwater?

Once cured, Flex Seal Epoxy—Extreme Liquid forms a durable, waterproof barrier; however, it will not work on wet surfaces or underwater.

How Long Does It Take for Flex Seal Epoxy to Dry?

Extreme Liquid: Sets at room temperature in 3–6 hours and cures in 15–24 hours.

What Are The Different Types of Flex Seal Epoxy?

Flex Seal Epoxy—Extreme Liquid is a multi-purpose, rapid-cure adhesive with a non-sag formula, ideal for overhead and vertical applications. It can fill gaps and cracks and cures to a permanent, watertight bond. This durable epoxy resists heat, chemicals, and impacts, ensuring long-lasting performance. The Extreme Liquid formula is available in a 25mL Syringe or a 14mL Squeeze Tube (2-Pack).

*Lift and strength tests were conducted in controlled environments for demonstration purposes only. Attempting to replicate these tests is extremely dangerous and strongly discouraged. Do not attempt.

What Color is Flex Seal Epoxy?

Extreme Liquid: Cures to black.

Flex Seal Epoxy: Product Attributes

• Super-strong: Extreme Liquid rated at 6,000 PSI; 1 gram can lift 16,000 lbs.* 
• Adheres to most surfaces.
• Forms a durable, waterproof barrier once cured.
• Can be applied to wet surfaces and underwater (Putty only).
• Fills gaps and cracks.
• Fast setting – Extreme Liquid: 3–6 hours.
• Ideal for overhead and vertical applications.
• Designed for extreme conditions, both indoor and outdoor.
• High-Heat Resistance: Up to 287.7°C for Liquid once fully cured.
• Impact, chemical, and fuel resistant.
• Simple to mix and apply.
• Once fully cured, can be sanded, drilled, or painted with high-quality latex paints.

*Lift and strength tests were conducted in controlled environments for demonstration purposes only. Do not attempt.

Recommended Application Surfaces:

• Metal
• Glass
• Wood
• PVC
• Ceramic
• Concrete
• Tile
• Fiberglass
• Brick
• Stone
• Rigid Plastics and more

Surfaces to avoid: Polyethylene, Polypropylene, Nylon, Mylar

Important Information About Flex Seal Epoxy:

• Not for flexible joints or moving cracks.
• Not food safe.
• Not aquarium safe.
• Uncured Epoxy should never be exposed to temperatures over 48.8°C.
• Do not thin Flex Epoxy with solvents, as it prevents curing.
• Product will NOT cure to a flexible coating.

How Do I Clean up Flex Seal Epoxy?

Clean-up (uncured product): Use a mild solvent like denatured alcohol and a clean cloth.

Cured: Remove mechanically (e.g., sanding)

How Do I Store Flex Seal Epoxy?

Storing Extreme Liquid in a Syringe: Pull the plunger back slightly, wipe the nozzle clean, and replace the “Snap & Save” cap securely. Remove excess epoxy with a clean, dry cloth.

Extreme Liquid should be stored in a cool, dry, climate-controlled area between 10°C and 32.2°C.

Storing Ultimate Putty: Store in a cool, dry place between 5°C and 25°C, with humidity between 30% and 70%. To prevent contamination, do not return used putty to its original container.

And there you have it. Now you’re ready to use Flex Seal Epoxy for all sorts of DIY projects and repairs. For additional questions or concerns, please visit our FAQ page or contact customer service at 833-411-3539.