For regular cleaning of slate, there’s no magic trick—just rinse it with clean water and give it a light scrub with a brush if needed.

Whether the slate is glued to concrete, laid on gravel/sand, or on pedestals (so-called system floors), outdoor slate usually only needs to be washed with a hose.

The most important tip: choose the garden hose over a pressure washer!

If you do use a pressure washer, avoid concentrating too close to the slate, as it could cause the mica layer on top to flake off or shift, leading to color changes or streaks from the spraying pattern.

Pressure washing can also damage grout if the slate is glued down, which could lead to frost damage. If sand is used as joint material, strong pressure can easily wash it away. Any applied sealant may also be affected.

For ingrained dirt, light cement haze, oil, and grease stains, you can use a deep cleaner such as “Stenrens.” This is a highly concentrated cleaning solution that is acid-free and free of phosphates or lye. The surfactants are biodegradable.

How to Use (Akemi Stone Cleaner):

Dilute the cleaner with water, between 1:1 to 1:500, depending on the level of dirt.

Apply and let it sit for 10-20 minutes.

For heavy dirt, scrub with a brush.

Rinse thoroughly with water.

Moss thrives where moisture and shade are present. While it doesn’t damage slate, many prefer to remove it for aesthetic reasons. Moss only grows on the surface. Some species are loosely attached, while others cling tightly, but scrubbing is the best method for removal. To make it easier, dampen the slate a few hours before scrubbing.

Steps:

1. Wet the area. Tip: Add a bit of dish soap to reduce surface tension for easier work.
2. Wait a couple of hours.
3. Scrub with a stiff brush. Note: Do not use a steel brush, as it can leave rust marks on the slate!
4. Optionally, clean with a disinfectant like chlorine after removal.
5. Rinse thoroughly.

A useful product for organic stains like wine, fruit juice, coffee, tea, moss, berries, blood, etc., is Akemi Good-Bye Stain.

How to Use:

• Remove residue mechanically.
• Apply generously with a cloth or sponge.
• Let it sit for 10-30 minutes, but don’t let it dry.
• Rinse with clean water and brush.
• Repeat if necessary, and allow longer exposure if needed.

For oil and grease stains, use a grease removal paste. Outdoor slate will naturally clear the stain over time, but this product speeds up the process.

How to Use (Akemi Grease Removal Paste):

• Ensure the surface is completely dry (recommended temperature: 5°C to 25°C).
• Apply a layer of at least 1-2 mm thick with a brush or spatula.
• Let the paste dry.
• Scrape or brush off the dried residue.
• Repeat if necessary for stubborn stains, and finish by cleaning with Stone Cleaner.

Tip: If you have slate under the grill or in another area prone to oil spills, we recommend sealing the surface to prevent stains. Sealing is a quick and easy process—check out our video and description showing how to do it

For these types of stains, use Akemi Graffiti Remover.

How to Use:

• Ensure the surface is dry. Best temperature: 10-30°C. Avoid direct sunlight.
• Apply evenly with a brush.
• After about 10-15 minutes, the paint should be soft enough to wash off with warm water.
• For heavy contamination, reapply, scrub with a natural bristle brush, and rinse thoroughly.

For rust stains, use Akemi Rust Remover.

How to Use:

Ensure the surface is completely dry.

• Apply the product undiluted with a brush. Tip: To avoid new rust formation in untreated areas, or color differences, treat the entire stone surface.
• Let the product sit for up to 24 hours.
• Avoid letting the surface dry out—cover it with plastic if needed.
• Rinse thoroughly with water until all rust remover residues are gone.
• Repeat if necessary once the surface is dry again.

Tip: Seal the surface afterward to prevent water penetration, which can cause new rust stains.