West System 205 Fast Hardener

SKU:SWES-205-A

$38.95 USD

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18 in stock

Size: 205-A Pint

205-A Pint 205-B Quart 205-C Gallon (0.94 gal)

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205 is the fast hardener for West System 105 resin: 5:1 by volume, 9-12 minutes of pot life in a 100 g cup at 72°F (22°C), and it keeps curing down to 40°F (4°C). The default choice for bonding and repair work in cool weather or when you want to stack operations the same day.

Mixed with 105 it goes solid in 6-8 hours and reaches working strength in 1-4 days. Cured color is amber and it throws an amine blush as it cures, so it is the wrong pick for clear-coating brightwork; that job belongs to 207 special clear hardener. For longer open time in a warm shop, step over to 206 slow.

Buy the hardener size that matches your resin group (A pint for the quart, B quart for the gallon) so the 300 pumps meter correctly out of both cans.

Specifications

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Technical Specifications

Made in USAMix 5 parts 105 resin : 1 part hardener by volume

Resin TypeEpoxy hardener - fast (for 105 Resin)

Mix Ratio5 parts 105 resin : 1 part hardener by volume

ViscosityMixed 105/205: 975 cps @ 72°F

Pot Life9-12 min (100 g @ 72°F)

Full CureSolid in 6-8 hr; working strength 1-4 days

Cured ColorAmber-tinted; not for clear coating

Max Service TempHDT 118°F (cured 105/205)

Tensile Strength7,900 psi (cured 105/205, ASTM D-638)

Best ForRapid cure & cold weather - works down to 40°F

Country of OriginUSA

Compare Resins

Product	West System 205 Fast HardenerYou're viewingfrom $38.95	West System 206 Slow Hardenerfrom $34.61	West System 207 Special Clear Hardenerfrom $63.15
Type	Epoxy hardener - fast (for 105 Resin)	Epoxy hardener - slow (for 105 Resin)	Epoxy hardener - special clear, blush-free (for 105 Resin)
Mix Ratio	5 parts 105 resin : 1 part hardener by volume	5 parts 105 resin : 1 part hardener by volume	3 parts 105 resin : 1 part hardener by volume
Viscosity	Mixed 105/205: 975 cps @ 72°F	Mixed 105/206: 725 cps @ 72°F	Mixed 105/207: 760 cps @ 72°F
Pot Life	9-12 min (100 g @ 72°F)	20-25 min (100 g @ 72°F)	22-26 min (100 g @ 72°F)
Full Cure	Solid in 6-8 hr; working strength 1-4 days	Solid in 10-15 hr; working strength 1-4 days	Solid in 10-15 hr; working strength 1-4 days
Cured Color	Amber-tinted; not for clear coating	Amber-tinted; not for clear coating	Exceptionally clear - won't cloud in humidity (blush-free)
Max Temp	HDT 118°F (cured 105/205)	HDT 123°F (cured 105/206)	HDT 117°F (cured 105/207)
UV	—	—	Contains a UV inhibitor; topcoat with UV varnish for lasting bright finishes
Best For	Rapid cure & cold weather - works down to 40°F	Extended working time & warm shops; minimum 60°F	Clear-coating natural wood & carbon fiber; minimum 60°F
	Selected	View	View

What's the difference between fast and slow epoxy hardener?

Hardener speed sets your working time and cure time, not the final strength. A fast hardener like West 205 gives a short pot life, around 9 to 15 minutes, and cures quickly, which suits cool weather and small batches. A slow hardener like West 206 stretches working time and cures well in heat. Match the hardener to your temperature and batch size, and keep the ratio the maker specifies.

Why are there different epoxy mix ratios like 5:1, 4:1, 3:1, and 2:1?

The ratio is fixed by the resin and hardener chemistry, not by strength, so each system has its own ratio you must follow exactly. West System uses 5 parts resin to 1 part hardener, while our Boat Suppliers hardeners come in 2:1, 3:1, and 4:1 versions. A lower ratio like 2:1 means more hardener by volume and is easier to measure. Choose cure speed by hardener type, never by changing the ratio.

How do I mix epoxy resin and hardener properly?

Follow the specific mix ratio provided by the manufacturer (commonly 2:1 or 1:1 by volume). Mix thoroughly in a clean container, scraping the sides and bottom, until the blend is uniform and streak-free.

What is amine blush and how do I remove it?

Amine blush is a waxy film that forms on curing epoxy as it reacts with moisture and carbon dioxide in the air, most often in cool, humid conditions. Left on, it blocks adhesion of the next coat, paint, or gelcoat. Wash the cured surface with plain water and a Scotch-Brite pad, dry it, then sand. West System 207 hardener is formulated to resist blushing.

Can I apply epoxy resin in cold weather?

Yes, but cold slows the cure and thickens the resin. Below about 60°F most epoxies cure slowly and can stay tacky, and below freezing they may not cure at all. Warm the resin and hardener to room temperature before mixing, heat the work area, and choose a fast hardener for low temperatures. Never add solvent to thin cold epoxy, since that weakens the cured bond.