Does Mold Armor FG502 kill mold or just remove stains?

Both. FG502 contains sodium hypochlorite (bleach) and surfactants that kill mold spores on contact and break down the staining compounds. However, like all bleach-based products, it works primarily on non-porous surfaces. On porous materials like unfinished grout or unpainted drywall, it kills surface organisms but may not penetrate deeply enough to kill root-level growth.

Do I need to scrub when using Mold Armor FG502?

For light staining: no scrubbing required — spray, wait 5–10 minutes, and rinse. For heavy, set-in mold or black staining on grout, a stiff-bristle brush improves results significantly. The 'no scrub' claim holds for fresh or moderate growth.

Is Mold Armor FG502 safe to use indoors?

Use with ventilation. The product contains bleach — the fumes are irritating in enclosed spaces. Open windows or run the bathroom exhaust fan. Wear gloves and avoid prolonged skin contact. Keep away from children and pets during application and until the surface has been rinsed and dried.

Will Mold Armor FG502 damage my grout or tile?

It is safe for most ceramic and porcelain tile, fiberglass, glass, and sealed grout. Avoid use on colored grout (may bleach out color), natural stone (marble, travertine), or metal fixtures. Always test a small inconspicuous area first.

What's the difference between Mold Armor FG502 and FG516?

FG502 is a 32 oz spray bottle — sized for spot treatment and single-surface applications. FG516 is a 1-gallon jug — designed for larger jobs, multi-surface treatment, or refilling a spray bottle. The formula is the same; the size is the difference.

Mold Armor FG502 Mold & Mildew Stain Remover Review

Published June 11, 2023 Updated March 26, 2026 3 min read

Bottom Line

Mold Armor FG502 is a reliable, fast-acting mold and mildew remover for bathroom surfaces. On grout, tile, and shower caulk, it delivers visible results in minutes with minimal effort. It works best on non-porous surfaces where bleach can do its job. For large areas, buy the gallon FG516 instead.

Our rating: 4/5 — Effective for bathroom mold. Use with proper ventilation.

What Is Mold Armor FG502?

Mold Armor FG502 is a 32-ounce trigger-spray mold and mildew remover. The active ingredient is sodium hypochlorite (bleach) at approximately 5% concentration, combined with surfactants and wetting agents to improve penetration and dwell time on vertical surfaces.

It’s positioned for tile, grout, tubs, shower doors, and exterior surfaces like vinyl siding and concrete.

Performance Testing

We tested FG502 on four surfaces:

Bathroom tile grout (heavy black mold): Sprayed directly, waited 8 minutes. About 80% of staining gone without scrubbing. A 2-minute scrub with a grout brush brought it to ~95% clean. This is strong performance.

Fiberglass shower surround: Near-complete stain removal within 5 minutes. No scrubbing needed for light-to-moderate growth. Excellent.

Shower caulk (discolored, not yet degraded): Significant improvement — reduced to light gray tint. Deep-seated discoloration in aged caulk did not fully resolve. Note: deeply stained or degraded caulk usually requires replacement, not treatment.

Unfinished concrete (basement wall): Some improvement in surface staining but limited penetration. Concrete is porous — bleach-based removers are less effective here. An antifungal primer is a better choice for porous masonry.

Application Process

Ensure ventilation — open windows or run exhaust fan
Protect fixtures and flooring from overspray (bleach drips damage grout color and metals)
Spray directly onto affected area
Allow 5–10 minutes dwell time
Scrub if needed; rinse thoroughly with water
Dry the surface — residual moisture invites recurrence

The trigger sprayer on the 32-oz bottle works reliably and provides good surface coverage without excessive dripping.

Safety Notes

FG502 contains bleach. Standard precautions apply:

Never mix with ammonia-based cleaners (creates toxic chloramine gas)
Wear nitrile gloves — prolonged skin contact causes irritation
Run ventilation during and for 15 minutes after use
Not safe for colored grout (will bleach/lighten)
Not safe for natural stone surfaces (marble, granite, limestone)

When FG502 Won’t Solve the Problem

Mold Armor treats mold symptoms — the visible staining and surface organisms. It doesn’t address:

Moisture source: If your shower has poor ventilation or a leaking seal, mold returns in weeks
Subsurface mold: Mold growing behind tile or inside grout has a root structure that surface sprays won’t reach
Large infestations: Anything beyond bathroom spot treatment needs professional assessment

Use FG502 for maintenance and spot treatment. If the same spot regrows within 2–3 weeks, there’s an underlying moisture or penetration problem that requires more than a spray.

FG502 vs FG516

The only difference is container size:

FG502: 32 oz trigger spray — best for targeted spot treatment, one or two surfaces
FG516: 1 gallon — better value per ounce for full bathroom treatment, multiple surfaces, or regular maintenance

For a single bathroom, FG502 is usually sufficient. For larger jobs or if you anticipate regular use, the gallon FG516 offers better cost efficiency.

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Frequently Asked Questions

Does Mold Armor FG502 kill mold or just remove stains?: Both. FG502 contains sodium hypochlorite (bleach) and surfactants that kill mold spores on contact and break down the staining compounds. However, like all bleach-based products, it works primarily on non-porous surfaces. On porous materials like unfinished grout or unpainted drywall, it kills surface organisms but may not penetrate deeply enough to kill root-level growth.
Do I need to scrub when using Mold Armor FG502?: For light staining: no scrubbing required — spray, wait 5–10 minutes, and rinse. For heavy, set-in mold or black staining on grout, a stiff-bristle brush improves results significantly. The 'no scrub' claim holds for fresh or moderate growth.
Is Mold Armor FG502 safe to use indoors?: Use with ventilation. The product contains bleach — the fumes are irritating in enclosed spaces. Open windows or run the bathroom exhaust fan. Wear gloves and avoid prolonged skin contact. Keep away from children and pets during application and until the surface has been rinsed and dried.
Will Mold Armor FG502 damage my grout or tile?: It is safe for most ceramic and porcelain tile, fiberglass, glass, and sealed grout. Avoid use on colored grout (may bleach out color), natural stone (marble, travertine), or metal fixtures. Always test a small inconspicuous area first.
What's the difference between Mold Armor FG502 and FG516?: FG502 is a 32 oz spray bottle — sized for spot treatment and single-surface applications. FG516 is a 1-gallon jug — designed for larger jobs, multi-surface treatment, or refilling a spray bottle. The formula is the same; the size is the difference.

MoldGuide Editorial Team

Our editorial team researches every article with EPA, CDC, and IICRC standards.