Ark Composites 2:1 Epoxy Hardener Medium
Ark Composites 2:1 Epoxy Hardener Medium is the all-round hardener for Ark Composites 2:1 Epoxy Resin, balancing working time and cure speed. Mixed 2 parts resin to 1 part hardener, it gives 10–15 minutes of pot life and 20–40 minutes of working time at 22 °C (71 °F), is sandable in 8–12 hours and reaches full cure in 2–7 days. Use it to coat and waterproof wood and metal, laminate fiberglass, carbon and Kevlar, and glue, fill and fair with fillers.
Features
- Balanced speed: 20–40 minutes working time at 22 °C (71 °F)
- Sandable in 8–12 hours; full cure in 2–7 days at 22 °C (71 °F)
- Same 2:1 by volume (100:43 by weight) ratio as ARK Fast and Slow
- Clear, no-blush, low-viscosity system; no blush wash needed unless working in freezing rain
- Works with fillers such as ARKTHIX, colloidal silica and micro balloons
- Strong when cured with ARK Epoxy Resin: 7,600+ psi tensile and 14,300+ psi flexural strength, 84–85 Shore D hardness (lab tested)
Recommended Uses
- Coating and waterproofing wood, metal and most porous surfaces
- Laminating fiberglass, carbon and Kevlar
- Fiberglassing canoes, kayaks and small boats
- Gluing, filling and fairing with fillers
How to Use
- Prep: surfaces must be clean, dry and free of oil, wax and paint. Wipe with acetone and a clean cotton cloth, and sand cured epoxy, fiberglass, metal and plastics. Do not use Varsol or petroleum-based solvents.
- Measure: 2 parts ARK Epoxy Resin to 1 part ARK Hardener with graduated containers. Don’t guess: too much or too little hardener will prevent a proper cure.
- Mix: mix thoroughly, scraping the sides and bottom of the container, then add fillers if desired. Pour into a paint tray or other flat container to extend the working time, and mix only what you can use within the pot life.
- Apply: spread with a solvent-resistant brush, roller or squeegee.
- Recoat: apply the next coat as soon as the previous one is tacky, between 2 and 6 hours depending on the hardener and temperature. After 8 hours, or once the epoxy has cured hard, sand with 80-grit paper before applying more epoxy or other coatings.
- Finish: let the epoxy reach full cure before painting or varnishing (2–7 days at 22 °C / 71 °F, all hardeners). Two-part polyurethane paint works best over epoxy; cured epoxy will chalk in sunlight if left unprotected by varnish or paint.
Specifications
| Property | Details |
|---|---|
| Brand | Ark Composites |
| Type | 2:1 epoxy hardener (Part B), medium speed |
| Use with | Ark Composites 2:1 Epoxy Resin |
| Mix ratio by volume | 2:1 resin to hardener (100:50) |
| Mix ratio by weight | 100:43 |
| Pot life @ 22 °C / 71 °F | 10–15 min |
| Working (gel) time @ 22 °C / 71 °F | 20–40 min |
| Sandable @ 22 °C / 71 °F | 8–12 hrs |
| Pot life @ 12 °C / 54 °F | 20–30 min |
| Sandable @ 12 °C / 54 °F | 12–20 hrs |
| Full cure @ 22 °C / 71 °F | 2–7 days |
| Recoat window | 2–6 hrs while tacky; after 8 hrs sand with 80-grit |
| Available sizes | 4 oz (118 mL) to 1 gal (3.78 L), 6 sizes |
Technical Data (with ARK Epoxy Resin)
| Property | Imperial | Metric |
|---|---|---|
| Viscosity @ 25 °C | Medium Hardener (Part B): 100–200 cps; mixed: 300–700 cps | |
| Specific gravity | Medium Hardener (Part B): 0.96–0.98; mixed: 1.08–1.10 | |
| Mix ratio by volume | 2:1 (100:50) | |
| Gel time, 150 g mass in cup @ 22 °C | 15–20 min | |
| Tensile strength (ASTM D638) | 7,617 psi | 52.5 MPa |
| Tensile modulus (ASTM D638) | 163,464 psi | 1,127 MPa |
| Elongation at break (ASTM D638) | 6.6% | |
| Compressive strength (ASTM D695) | 10,558 psi | 72.8 MPa |
| Compressive modulus (ASTM D695) | 232,985 psi | 1,606 MPa |
| Flexural strength (ASTM D790) | 14,339 psi | 98.9 MPa |
| Flexural modulus (ASTM D790) | 459,688 psi | 3,169 MPa |
| Hardness (ASTM D2240) | 84–85 Shore D | |
Typical lab values for ARK Epoxy Resin cured with this Medium Hardener. These are not specifications. Liquid properties are measured at 25 °C. Gel time is a lab test of a 150 g mass in the cup, not working time on the job. Metric values are converted from psi.
Hardener Selection & Cure Times
At 22 °C / 71 °F
| Hardener | Pot life | Gel time | Sandable | Full cure |
|---|---|---|---|---|
| Fast | 8–10 min | 15–20 min | 6–8 hrs | 2–7 days |
| Medium | 10–15 min | 20–40 min | 8–12 hrs | 2–7 days |
| Slow | 15–20 min | 30–60 min | 15–24 hrs | 2–7 days |
At 12 °C / 54 °F
| Hardener | Pot life | Sandable |
|---|---|---|
| Fast | 15–20 min | 10–14 hrs |
| Medium | 20–30 min | 12–20 hrs |
| Slow | 35–40 min | 24–48 hrs |
All three hardeners mix with ARK Epoxy Resin at 2:1 by volume (100:50) and 100:43 by weight. Pot life, gel and sanding times vary with temperature, mixed volume, time in the mixing container and laminate thickness: they roughly double for every 8 °C (about 14 °F) drop in temperature and halve for every 8 °C rise.
Safety and storage: ARK Epoxy Resin (Part A) is labelled WARNING: harmful if swallowed; causes skin irritation and serious eye irritation; may cause an allergic skin reaction. ARK Hardener Medium (Part B) is labelled DANGER: causes severe skin burns and eye damage; may be corrosive to metals; may cause allergy or asthma symptoms or breathing difficulties if inhaled; may cause an allergic skin reaction; may cause damage to organs (lungs, kidneys) through prolonged or repeated exposure. Vapours and mists are corrosive to the respiratory tract. Wear chemical-resistant (nitrile) gloves, chemical splash goggles (no contact lenses) and long sleeves, and work in a well-ventilated area; do not breathe vapours or mists, and use an approved respirator if ventilation is inadequate. Clean epoxy off skin with soap and water, never solvents. Store at room temperature in the original, tightly closed containers, upright and off concrete floors; keep hardeners locked up and away from metals; do not freeze. For safety information, refer to the Safety Data Sheet below.
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For more info on ARK Resin Application refer to the TDS sheet below.
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Data Sheets
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