Two jobs, two kinds of product
A repair filler fills a defect: a nail hole, a crack, a gouge or a missing corner. A grain (or pore) filler fills the open vessels of ring-porous woods so that a film finish lies flat; the Forest Products Laboratory notes that large vessels can leave thin, low spots in a film. They are not interchangeable, and neither is a substitute for the other.
| Filler | Example | For | Times | Stain or paint |
|---|---|---|---|---|
| Repair filler, soap-and-water cleanup | Minwax Stainable Wood Filler | Holes, cracks, gouges in unfinished wood, in or out | Dry 2–6 h by size | Takes Minwax stains; topcoat or paint |
| Putty for finished wood | Minwax Wood Putty | Small marks in finished wood | Does not harden | Precoloured |
| Two-part polyester | Minwax High Performance Wood Filler | Split, damaged or rotted wood, in or out | Work 10 min; carve 20; sand 30 | Stain after sanding no finer than 100; prime before paint |
| Epoxy putty and consolidant | Abatron WoodEpox and LiquidWood | Decayed or missing wood | Not stated on the page reviewed | Paintable, machinable |
| Clear grain filler | Aqua Coat Clear Wood Grain Filler | Open pores before a film finish | Touch 60 min; sand and recoat 1–2 h | Stain before or after |
From Minwax's product guide and data sheet, Abatron's product page and Aqua Coat's data sheet. Aqua Coat's times are at 70°F and 50% RH; Minwax's polyester times are at room temperature.
Repair fillers
- For small defects in bare wood, Minwax's stainable filler dries in 2 to 6 hours depending on the size of the fill, cleans up with soap and water and, Minwax says, accepts its penetrating stains and any of its clear finishes. Minwax does not recommend it for hardwood floors.
- For finished wood, Minwax sells a separate putty that comes in colours and never hardens — a touch-up, not a structural fill.
- For damaged or rotted wood, two-part fillers cure by reaction. Minwax's polyester version stays workable for about 10 minutes and can be sanded after 30; Minwax says to treat soft, rotted wood with its hardener first. Abatron's epoxy system pairs a penetrating consolidant with a shrink-free putty in the same way.
- Stain will not match exactly. Minwax's own data sheet says no filler, once stained, will exactly match the wood, and says to sand its polyester filler no finer than 100 grit before staining it. Test on scrap, and where colour matters, consider placing the repair where it shows least.
The Forest Products Laboratory adds that a repair filler should stay flexible when cured, to move with the wood as its moisture content changes. Matching a product to a particular repair is the subject of choosing a wood filler.
Grain filler
Grain filler matters on woods with large pores. The Forest Products Laboratory lists ash, hickory, oak and walnut as large-pored, aspen, cherry and maple as small-pored, and softwoods as having none. Aqua Coat's clear gel is worked into the pores with a putty knife or card, scraped off with the grain, and given a second coat after a light 320-grit sanding; it wants overnight before the final finish.
- Over stain: Aqua Coat says oil-based stain needs 48 to 72 hours to dry first, and water-based stain a seal coat of dewaxed shellac — such as Zinsser's SealCoat — before the filler.
- Under the topcoat: grain filler is the base, not the finish; a clear coat goes over it. See polyurethane and shellac and lacquer.
Safety— Two-part fillers
Minwax's polyester filler is labelled combustible, with harmful vapour; its hardener contains benzoyl peroxide. The data sheet calls for ventilation, safety glasses and rubber gloves. Mix only what the label says can be used in the working time.
Choosing a filler
- A defect to fill, or open pores to level
- Bare or finished wood, indoors or out
- Rotted wood consolidated first, as the maker says
- Stain tested over the filler on scrap
- The maker's sanding grit before stain or paint
- Working time known before mixing a two-part filler
Sources
Working and drying times are each maker's for its own product, at room temperature or the conditions given; Minwax and Aqua Coat both say cooler temperatures lengthen them. No filler was tested for this page.
- 1.
Minwax Product Guide. Minwax.
Used for: Stainable Wood Filler for nail holes, cracks, gouges and knot holes in unfinished wood indoors and out: 2–6 h to dry by size, soap-and-water cleanup, accepts Minwax penetrating stains, can be topcoated or painted, not for hardwood floors or under PolyShades; Wood Putty for finished wood, precoloured and never hardening.
- 2.
Technical Data Sheet, Minwax High Performance Wood Filler. Minwax.
Used for: High Performance Wood Filler as a two-part polyester (styrene) filler for split, damaged or rotted wood, indoors or out: workable about 10 minutes, carvable after 20, sandable after 30; Wood Hardener first on rotted wood; sand no finer than 100 grit before staining; prime before painting; 'No wood filler when stained will exactly match the color of the original wood'.
- 3.
Abatron Wood Restoration Kit: LiquidWood and WoodEpox. Abatron (UC Coatings).
Used for: LiquidWood as a penetrating epoxy consolidant that hardens decayed wood, and WoodEpox as a shrink-free epoxy putty to fill and replace missing wood, machinable and paintable.
- 4.
Technical Data Sheet, Clear Wood Grain Filler (130-099). Aqua Coat.
Used for: A water-based clear gel grain filler for open pores: applied with a putty knife or card and scraped off with the grain; 60 minutes to touch, sand and recoat in 1–2 h at 70°F and 50% RH; two coats; 320 grit before each coat; overnight before topcoats; stain before or after, with oil-based stain dry 48–72 h first and a dewaxed-shellac seal coat over water-based stain.
- 5.
Christopher G. Hunt. Wood Handbook: Wood as an Engineering Material (FPL-GTR-282), Chapter 16: Finishing Wood. USDA Forest Service, Forest Products Laboratory, 2021.
Used for: Large vessels in ash, hickory, oak and walnut, small ones in aspen, cherry and maple, none in softwoods; vessels leaving thin, low spots in film finishes; fillers as paste or liquid, lightly sanded; repair fillers that should stay flexible when cured.
- 6.
Technical Data BEY-07, Bulls-Eye SealCoat Universal Sanding Sealer. Rust-Oleum (Zinsser).
Used for: SealCoat as a 100% dewaxed shellac compatible with all clear topcoats.
About this guide
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