General Finishes High Performance delivers award-winning durability in a flat sheen water-based topcoat, solving the usual trade-off between matte aesthetics and protective performance. This urethane/acrylic blend earned Fine Woodworking’s vote as the hardest, most durable consumer polyurethane — not bad for a finish that looks like it has no finish at all.
Skip it if you’re coating bright white paint or need an outdoor finish. The formula can yellow over bright whites, and this is strictly an interior product despite the “high performance” name.
Performance That Backs Up the Awards
The Koenig hardness rating of 59 puts this finish well above typical flat topcoats. High Performance is significantly harder and more durable than General Finishes’ own Flat Out Flat, which trades durability for that soft, wax-like feel some folks prefer.
The numbers tell the story:
| Specification | High Performance Flat | Source |
|---|---|---|
| Hardness (Koenig) | 59 | manufacturer |
| Wear Resistance (Taber) | 34.40 mg loss | manufacturer |
| Chemical Resistance | 93/105 | manufacturer |
| Water Resistance | 4/5 | manufacturer |
| Sheen Level | Approximately 10° | manufacturer |
The urethane/acrylic chemistry differs from Flat Out Flat’s self-cross-linking acrylic — that’s what gives High Performance its superior hardness while maintaining clarity. For an even flatter look, their Dead Flat variant drops the sheen below 5°, though you’ll need to verify if that hardness holds up at the lower sheen.
Application Specs That Matter in Montana
The 2+ hour recoat time lets you build multiple coats in a single day — crucial when you’re racing Montana’s short finishing season. Medium viscosity at 350-450 cPs means it flows well but won’t run on vertical surfaces.
| Application Spec | Value |
|---|---|
| Coverage | 500-600 sq ft/gallon |
| Dry to Touch | 30+ minutes |
| Recoat Time | 2+ hours |
| Full Cure | 21 days |
| HVLP Tip Size | 1.1-1.3mm |
| Wet Film Thickness | 3-5 mil |
The critical step most folks miss: thorough stirring before and during use to reincorporate matting agents. Those matting solids settle fast. Skip the stirring and you’ll get uneven sheen that no amount of sanding can fix.
Between coats, sand with 220-320 grit after that 2-hour dry time. The finish sands beautifully — no gumming or loading like some water-based products. Apply 2-3 liberal coats, maximum 3. More coats won’t improve durability, just build unnecessary thickness.
The low odor and soap-and-water cleanup means you can spray cabinets in an occupied house without clearing everyone out. Try that with lacquer. VOC content under 175 g/L meets all 50-state requirements — no special ordering for California jobs.
Raw wood and water-based stains take the finish directly. Oil-based stains need 48 hours minimum cure time before topcoating. Don’t use it over linseed oil, Danish oil, or bright white paint — the chemistry doesn’t play nice.
This isn’t a garage floor coating or deck finish. It’s engineered for interior furniture, cabinetry, trim, and doors. The flat finish even works on interior hardwood floors in high-traffic areas, though most floor finishers will look at you funny for wanting flat on floors.
Frequently Asked Questions
Q: How does High Performance Flat compare to regular Flat Out Flat?
A: High Performance is significantly harder and more durable than Flat Out Flat. High Performance uses a urethane/acrylic blend while Flat Out Flat uses self-cross-linking acrylic. Flat Out Flat offers a more ‘wax-like’ soft touch feel, whereas High Performance has a standard poly feel. Choose High Performance for durability, Flat Out Flat for that soft hand-rubbed texture.
Q: Can I spray this finish with standard HVLP equipment?
A: Yes. Use a 1.1-1.3mm tip and target 3-5 mil wet film thickness. The medium viscosity of 350-450 cPs sprays well without thinning. Stir thoroughly before spraying — don’t shake, as this introduces bubbles.
Q: What’s the actual working time in Montana’s dry climate?
A: Dry to touch in 30+ minutes, recoat in 2+ hours. Low humidity speeds these times. Light use after 7-10 days, full cure at 21 days before heavy use or cleaning with solvents. Plan your project schedules accordingly.
Q: Will this yellow over white painted cabinets?
A: High Performance may cause yellowing over bright white paint — General Finishes recommends using their White Poly or Brushable products instead. The formula stays water-white and does not yellow over time on non-reactive substrates, but bright white paint is reactive.
Q: What about the warranty coverage?
A: General Finishes provides a limited warranty covering product defects with replacement or refund. The warranty excludes labor costs, color satisfaction, misapplication, incompatibility with other manufacturers’ products, and damage from surface contaminants like wax or silicone. Pretty standard warranty — they’ll replace defective product but won’t pay for your time or user errors.
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