Classic Coatings Systems Classic Coatings | Simple Stain (Dark Slate) | Concentrated | Water-Based, Semi-Transparent | Zero VOC, UV Stable | Interior/Exterior | Easy to Use, Fast Drying

Why I reached for this stain

I had a tired-looking garage slab and a sun-faded patio that needed a refresh without the plasticky look of paint. I wanted a semi-transparent finish that would keep the concrete’s character, hold up outdoors, and not gas me out indoors. That’s why I picked up Classic Coatings’ Simple Stain in Dark Slate. It’s a concentrated, water-based, zero-VOC stain you dilute with distilled water and spray or brush onto porous surfaces. It promises fast dry times, UV stability, and broad compatibility (concrete, brick, stone, stucco, wood, cement, plaster, pavers). On paper, it checked a lot of boxes.

Prep matters more than anything

This is a semi-transparent stain; it will highlight your surface—good and bad. I did a thorough degrease and scrub, rinsed well, and let the slab dry completely. On smooth, machine-troweled areas, I lightly sanded to open the surface. If you’re unsure whether your concrete is ready, do a water-drop test: beads mean it’s still sealed or contaminated; absorption within a minute means you’re in the right zone. Any old sealer will interfere with penetration, so remove or abrade it. Patch work also shows through, so manage expectations or intentionally embrace the variegation.

Tip: Mask aggressively. This stuff sprays as a fine mist and can fog onto doors, baseboards, and siding if you’re not careful.

Mixing: don’t rush it (and strain it)

As a concentrate, the stain needs to be diluted with distilled water according to the label. Here’s what made a noticeable difference in my results:
- Use a drill-mounted paint mixer to re-suspend pigments thoroughly before you dilute and again after you dilute.
- Strain the mixed stain through a fine paint filter into your sprayer. This prevents pigment seeds from clogging the tip or leaving dark specks on the slab.
- Keep the mixture agitated. I swirl the sprayer tank every few minutes. With a backpack sprayer, a quick shake between sections is enough.

I also recommend a quality backpack sprayer with a consistent pressure and a fan tip capable of a fine, even mist. Cheap garden sprayers often drip at the tip and create dots that dry darker. If you must roll, use a 1/4" microfiber cover and work quickly in light, even passes to avoid lap lines—spraying is easier to keep uniform.

Application: light, overlapping passes

Simple Stain flashes off quickly, so thin coats are your friend. I worked in 3–4 foot lanes and kept the nozzle 12–18 inches from the surface, moving at a constant speed. My approach:
1. First coat: light, even passes in one direction.
2. Second coat: after it flashed off (usually 30–60 minutes depending on weather), I applied a cross-coat at 90 degrees to even out the tone and reduce striping.
3. Optional: a light “fog” pass to soften transitions.

Don’t chase wet edges; let it do its thing. It often looks splotchy while wet and evens out as it dries. If you get a drip, resist the urge to roll it out while wet—that usually makes it worse. Let it dry, then feather with a light fog pass. Work out of direct sun and off hot slabs whenever possible to avoid premature drying and tiger striping.

Color and coverage

Dark Slate landed as a cool charcoal with a subtle blue-gray cast on my garage slab and a slightly warmer, lighter tone on the broom-finished patio. The porosity and base color of your concrete will swing the final shade far more than any screen swatch. If the exact tone matters, do a test area in an inconspicuous spot, including sealer if you plan to topcoat—gloss deepens the color.

Coverage will vary. On the denser garage floor, one light coat came close to the upper end of the spec for me, and the second coat pulled the total nearer to the 400–500 sq ft range per diluted gallon. On the more porous patio, I needed more material to get the richness I wanted. Plan conservatively and buy an extra container if your surface is thirsty—you can always save unopened concentrate for touch-ups later.

Compatibility and versatility

I used Simple Stain primarily on concrete, but I also tested it on a scrap of plaster and a piece of unsealed stone paver. It absorbed readily into both, though the tone shifted warmer on the plaster and darker on the paver. Wood will take the stain, but it reads differently than on mineral surfaces; think wash-of-color rather than deep penetration. The zero-VOC formula is genuinely low odor, making it comfortable for interior work with normal ventilation.

Sealing and durability

Unsealed, the finish has that mineral, in-the-surface look I like, but it won’t resist abrasion, oil, or tire marking in a garage. I sealed with a compatible water-based acrylic sealer: two thin coats, rolled. The sealer deepened the color slightly and added a uniform sheen. Outdoors, especially around a pool or on steps, add a non-slip grit to the final coat. UV stability in the pigment is helpful, but the topcoat is what protects against wear, stains, and chalking. Expect periodic maintenance; that’s the nature of stained concrete.

What I liked

• The look: Semi-transparent stains are all about subtle movement and variation. Dark Slate delivers a modern, soft-charcoal vibe without looking painted over.
• Low odor, easy cleanup: Zero VOCs and water-based cleanup made the whole process less of a production.
• Fast dry times: Moving from coat to coat in under an hour kept the project on schedule.
• Versatility: Works across a range of porous surfaces, indoors and out.

What to watch for

• Thorough mixing is not optional: Pigment can settle hard. Use a drill mixer and strain before spraying. Skimp here and you’ll fight clogs and specks.
• Application equipment matters: A backpack sprayer with a fine, consistent fan is worth it. Drippy nozzles cause dark dots that are hard to hide.
• Color shifts with the substrate: Always test. Differences in porosity and base tone can make Dark Slate read lighter or bluer than expected.
• Coverage varies: The published numbers assume a relatively tight surface. Rough, broomed, or very porous concrete will drink more material.
• Cost: As a concentrated, specialty stain, it’s pricier than big-box alternatives. The economy comes from the dilution and coverage—provided your surface isn’t extremely thirsty.

Practical tips for better results

• Clean until a white rag stays clean, then let the slab fully dry.
• Do the water-drop test; remove sealers or oil until water absorbs evenly.
• Mix with a drill and strain through a fine paint filter into the sprayer.
• Keep the sprayer pressurized; maintain a consistent distance and speed.
• Apply two light coats, cross-hatched, rather than one heavy coat.
• Let it dry completely before sealing; follow the sealer’s recoat and cure times.
• For safety on exterior steps or pool decks, add anti-slip grit to the final topcoat.

Bottom line

Simple Stain in Dark Slate delivers a clean, contemporary, semi-transparent finish that enhances rather than hides the substrate. It’s genuinely low odor, fast-drying, and versatile across surfaces. The tradeoff is that it rewards careful prep and technique. You need to mix thoroughly, strain the material, and use a decent sprayer to avoid clogging and dark specks. Color is substrate-dependent, so testing is key, and coverage can swing based on porosity.

Recommendation: I recommend this stain to DIYers and pros who want a natural, variegated look and are willing to put in the prep and use proper application tools. If you want a foolproof, paint-like, uniform color with minimal surface prep, or if you’re working on extremely porous or previously sealed concrete and can’t strip it, this isn’t the right product. Used correctly, though, Simple Stain produces a durable, attractive finish that elevates both interior and exterior concrete without the heavy-handed feel of paint.