Minwax High Performance Wood Filler and Minwax High Performance Wood Hardener are a two-step system for rotted, split and damaged wood indoors or out: windowsills, door frames, trim, railings and furniture. Wood Hardener is a thin liquid you brush into soft, decayed wood to bind the fibers and seal out moisture. Wood Filler is a two-part polyester filler you mix with its own cream hardener, then carve, sand, drill, paint or stain once it sets. Everything on this page comes from Minwax's technical data sheets, safety data sheets and product pages.
High Performance products we carry
Wood Hardener vs Wood Filler: specs from Minwax
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Wood Hardener |
Wood Filler |
| What it is |
Quick-drying liquid, synthetic resin in acetone and alcohol |
Two-part polyester filler (filler plus cream hardener in a tube) |
| Where |
Interior or exterior rotted wood |
Split, damaged or rotted wood, indoors or out |
| Apply with |
Disposable bristle brush, several coats until the surface looks shiny |
Plastic putty knife; mix about 16 parts filler to 1 part hardener |
| Timing |
Hardens in 2 to 4 hours, then fill |
Workable about 10 minutes; carve after about 20 minutes; sand, plane or file after 30 |
| Solids |
25% |
88% |
| Finish over it |
Fill with High Performance Wood Filler, then sand, paint or stain |
Paint (Minwax recommends a primer first) or stain |
| Clean up |
Acetone |
Regionally compliant cleaner (Minwax page) |
| Safety data sheet |
Danger: extremely flammable; flash point -4°F |
Danger: combustible; contains polyester resin and styrene; the hardener tube contains benzoyl peroxide |
How to repair rotted wood (Minwax directions)
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Remove the rot. Dig out decayed, very soft, crumbly wood until you reach reasonably sound wood. The wood should be dry and free of dirt, grease, oil and loose paint. Wear chemical-resistant rubber gloves and eye protection.
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Harden. Shake the Wood Hardener can well and brush it on until the soft wood is completely saturated. Apply several coats in quick succession until the surface looks shiny, then let it harden 2 to 4 hours.
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Mix the filler. Scoop filler into the plastic lid and add hardener from the tube at about 16:1. Mix about 30 seconds, until the white hardener streaks are gone. Mix only what you can use in 15 minutes.
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Fill. Spread a thin layer, then enough to fill the gap, and overfill slightly for sanding. For deep holes, build up 1/8 inch layers one at a time. Cold slows hardening; heat speeds it up.
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Shape and finish. Carve with a sharp knife after about 20 minutes. Sand, plane or file after at least 30 minutes, then prime and paint, or stain.
Staining the repair? Minwax says to sand lightly (no finer than 100 grit), stain right after the filler hardens, and leave a thick dab of stain on for at least an hour before wiping. No stained filler will exactly match the surrounding wood, so test in a hidden spot first.
Not rotted wood? For nail holes and small gouges in bare wood, see wood filler and wood putty. For nail holes in already-finished wood, see Minwax Wood Putty and Minwax Blend-Fil Pencils.
Shop related: all Minwax products, primers and sealers, prep, patch and repair and the furniture refinishing project cart.
FAQ
Do I need Wood Hardener before the filler?
Use it when the wood is soft or rotted. Minwax says it strengthens the wood fibers and forms a solid base for filling. Sound wood that is only gouged or split can go straight to the filler.
How long before I can fill over Wood Hardener?
Minwax says to let it harden 2 to 4 hours before filling with High Performance Wood Filler.
Is High Performance Wood Filler for outdoor repairs?
Yes. Minwax rates it for split, damaged or rotted wood indoors or out and calls it weather, water and rot resistant.
Can I use the filler to anchor screws or fix loose joints?
Yes. Minwax's data sheet says it is very effective as a wood adhesive and works for anchoring screws or securing loose joints in furniture.
Can I paint or stain it?
Yes, once it has hardened (about 30 minutes). Minwax recommends a primer before paint. It takes stain differently than wood, so an exact color match is unlikely.
Shipping and returns?
Orders of $35 or more ship free within the 48 contiguous states and Washington, DC. Wood Hardener is an extremely flammable liquid, so it can't be returned under our refund policy; check the size before you order. For the filler, see the same policy for return eligibility. If an order arrives damaged, defective or wrong, email Store@projectweekenddiy.com with photos and we will make it right.
Sources: Minwax High Performance Wood Filler technical data sheet (12/06) and Minwax High Performance Wood Hardener technical data sheet (03/07), both the current versions on paintdocs.com as of Nov 13, 2026; Minwax safety data sheets for UPC 027426416000 (rev 9/3/2026, v21) and 027426417007 (rev 8/9/2026, v17); High Performance Wood Filler and Wood Hardener product pages on minwax.com.
