How to Properly Clean Slate Tile Flooring

Slate is a metamorphic rock formed from a combination of various minerals and sediments compressed together over long periods, during which heat and pressure finally bond together all of those rock types and particles into a homogeneous stone.

This stone is formed from a combination of several types of stone and minerals such as quartz, mica, muscovite, calcite, biotite, chlorite, hematite, pyrite, and a few more that bonded together to provide the fine-grained, durable, but brittle stone that we know as slate.

Depending on which minerals form the slate and where it is from, its colors will vary from black, dark green, and gray, with occurrences of red, blue, purple, and gold. Instead of being cut to size like granite or marble, slate is cleaved along its natural graining, thus offering uneven and rough surfaces.

Referring mainly to its underside treatment, slate is generally graded as "ungauged" when left in this natural state. Ungauged slate has rough and uneven thicknesses varying between 1/8 inches and 1/2 inches, making its installation more difficult as it requires building up the tiles with adhesive on the back of the tile to make the surface flat and even.

"Gauged" slate, on the other hand, which has been ground down to a more consistent thickness of about 1/16 inches, offers a much more dependable and even surface requiring much less effort and installation skills.

Another classification of slate that will concern us more as it refers to the exposed surface of the tiles describes the amount of polishing that is added to the slate surface. It can vary from a rustic, natural look that preserves the slate's natural and ungauged appearance that is referred to as being "clefted."

A smoother finish of the surface can be achieved and is referred to as a "honed slate" and provides a more contemporary or modern look for flooring. Although not as glossy and shiny as marble, the honed slates are polished to a smooth glossy finish.

Polished slates have the highest degree of shine and gloss, but they are quite rare.

Slate, being a non-porous stone, requires less maintenance than other natural stones, such as marble or granite, which are porous. Their porosity makes them susceptible to the absorption of liquids like wine, juice, or oil that won't affect slate surfaces.

Identifying Natural Stone

Natural stone is actually divided into two general categories that don't necessarily tolerate the same cleaning procedures. Categorized by their natural composition, you have Siliceous stone and Calcareous stone.

Siliceous Stones

Siliceous stones are largely made up of silica. The different stones in this category include granite, sandstone, quartzite, brownstone, bluestone, and of course, slate are more durable and easier to clean with mild acidic cleaning solutions.

Calcareous Stones

Marble, travertine, limestone, and onyx are several different types of calcareous stones, mainly composed of calcium carbonate. Calcareous stone is sensitive to acidic products and should only be cleaned with mild non-acidic cleaners.

You can identify siliceous stone from calcareous stone with a very simple sensitivity test to acid. You simply mix 1/2 ounce of muriatic acid (white vinegar) with 5 ounces of water (diluted 10 to 1) and then apply a few drops to the stone surface using an eye dropper.

The test should be conducted in a concealed area, such as inside a closet or hidden corner, and the stone shouldn't have had any prior sealant or wax on it. If there was sealer or polish, chip off small pieces of the surface where you can apply the solution.

Caution: since muriatic acid is corrosive and is considered hazardous, you should wear protective eyewear and gloves, and keep the area well-ventilated while doing the test.

Clean the application area thoroughly, then apply the drops to a small (coin-size) spot of the chipped or selected area. If the acid drops from the eye dropper start bubbling or fizzing, the stone is definitely calcareous. If the reaction is mild to none, the stone can be considered siliceous.

Regular Care of Your Stone Floor

Regardless of the type, any stone floor surface should be cleaned frequently using a non-treated dust mop, sweeping, or vacuuming. The dust and dirt that is being drugged from everybody's footwear can be very abrasive and damage the stone surface.

Using mats at the door can also greatly limit the amount of dirt drug on the stone surface.

Step 1 - Dust Mopping and Sweeping Slate

Frequent cleaning of slate floor tiles with a dust mop and a broom will keep your floor free of dirt and dust that would otherwise wear off the protective sealer coating that would normally protect and enhance your flooring for many years.

Dust mopping your slate floor should ideally be done on a daily basis. This first step sounds quite easy as every home has a dust mop that most people have used already.

But as simple as it sounds, there is a specific technique to follow with the dust mop and a broom to ensure that your floor doesn't end up with buildups of dust and grit in certain areas of your floor.

Using a vacuum cleaner can also provide a great solution if done with care. But be careful here about the vacuum cleaner's accessories that come in contact with the slate.

The vacuum cleaner brush as well as the broom bristles should be soft. You shouldn't use carpet cleaning accessories or a carpet vacuum with a drum beating against the stone, etching and damaging the surface.

The cleaning should be started first with the dust mop. A dust mop with a clean high-quality microfiber pad will ensure a thorough cleaning removing all dust and dirt from any crevices.

The dry mopping should be started at one end while pushing in a straight motion toward the other direction. Avoid moving it back and forth or using circular motions, as this would simply spread the dirt around.

Mentally divide your floor area into specific sections, dry mopping one section at a time and sweeping up the dirt accumulation with a soft bristle broom. You can then overlap over the last section when you proceed to the next one and repeat the process.

Keeping more than one machine-washable high-quality insert will ensure that you always have one ready for the daily chore.

Step 2 - Mopping a Slate Floor

Mopping a slate floor is also part of the regular slate stone care and should be done on a monthly basis. Washing and scrubbing the slate should always be done with clean water and a soapless cleaner.

Some might suggest the use of mild, phosphate-free, bio-degradable dishwashing or stone soap which are totally acceptable, providing that you thoroughly rinse the whole surface afterward to prevent the suds from forming an undesirable film on the stone surface.

It should be mentioned though that mopping the floor does not translate into soaking it with water. Quite on the contrary, you should not leave large water puddles to form or leave water or spills on the floor, which should instead be wiped up right away.

The spin mop is a very handy tool that effortlessly wrings it out, leaving you with only a damp mop to proceed.

Mix your cleaner or soap in your bucket of warm water. A quality commercial product is highly suggested here, to provide optimum results—just follow the mixing instructions on the container.

With the water and the cleaning agent properly mixed, dip your mop in your bucket until it is properly soaked, and then wring it out to remove all excess water from it.

The damp mop can then be passed over the tiles in smooth slow strokes as you progress across the floor. Rinse the mop often to keep it clean, and as soon as it shows streaks of dirt on the floor, dump out the dirty water and replace it with a fresh mix.

If you chose to use a detergent or other kind of soap in your mix, once you're finished washing the floor, you'll have to replace your water with fresh, clean water a rinse the floor thoroughly, making sure it is free of any remnant traces of soap.

Once you've removed all traces of any cleaning solution, you can wipe the floor dry with a soft cloth or towel to avoid any standing water from seeping in. Leave it completely dry overnight before walking on it.

Another alternative for cleaning your floor is using a steamer to steam clean your slate. Steam cleaning the stone will provide you with a deeper clean as it can pick up deeply lodged dirt particles from the tiles and the grout and effectively disinfect your floor. Homes with family pets can particularly benefit from this advantage.

Products That Are Safe to Clean Slate

1 - Mild Detergent

If the stains and marks are minor, start by using the same cleaning solution you are scrubbing the floor with. You can simply rub the spot with a small brush dipped in the cleaning agent.

2 - Isopropyl Alcohol or Rubbing Alcohol

Isopropyl alcohol is a compound highly soluble in water to produce a solution at 70% or 90% concentration. A mixed solution of rubbing alcohol is widely used for medical reasons as an antiseptic, to relieve muscle pain, or as a disinfectant for some medical instruments.

But it can also be effective as a household cleaner for removing some stains, as a mixture in the proportions of 1:8 with water. Just soak a sponge or a clean cloth into the solution before rubbing on the stain.

A word of care, though, while you're working with cleaning products—avoid using with bleach, as this would cause a highly toxic by-product.

3 - Hydrogen Peroxide

In use for almost a century in most households, hydrogen peroxide has always been recognized as a super cleanser for medical as well as household use although its use has been greatly reduced for wounds and skin care, as it alters and slows the healing process.

Hydrogen peroxide only differs from water by the extra oxygen molecule added to it, but this addition at the molecular level converts the solution into a powerful oxidizer. It is much safer to use than chlorine and bleach, however, since it tends to break down quickly after coming in contact with air or water.

Although it's only a mild bleach that will not etch or damage slate, it could still bleach the color out of colored grout. You should first try the solution in an inconspicuous area of the floor for a colorfast test.

Hydrogen peroxide can kill many organisms, such as yeast, fungi, bacteria, mold spores, and viruses. Mixed in equal parts with water, it can be applied to a stain using a spray bottle and letting it sit and fizz for at least 10 minutes. You can then scrub it with a brush or a sponge before rinsing it thoroughly with clean water.

4 - Baking Soda and Peroxide

Both baking soda and peroxide are relatively safe for slate flooring. Mixed together in equal amounts until it forms a paste, the compound makes an effective agent that can lift and dissolve some of the more stubborn dirt and grease stains.

Once you have the paste thoroughly mixed, wait until it stops bubbling, then apply it to the stained area and let it set for a few minutes before wiping it with a clean cloth.

5 - Shaving Cream

Shaving cream or foam has more uses around the house than you might think. The combination of stearic acid and triethanolamine works effectively together to draw out the dirt, remove the grime, and degrease surfaces.

As a cleanser, it can be used on many different surfaces, such as glass, mirrors, stainless steel, jewelry, ovens, stovetops or hobs, upholstery, carpets, tiles, and grout.

If your slate floor's grout is colored, shaving foam or cream could be your go-to option to remove stains and blemishes from the floor. But first, do a spot check in an inconspicuous area of your floor. Apply a fair amount of shaving cream onto the stain and let it sit for 15 minutes, then wipe it off with a clean cloth soaked with warm water.

6 - Clay-Based Cat Litter

It can be surprising what an absorbent material such as kitty litter can do to remove old and new stains.

6.1 - First clean the affected area to remove all dirt and debris.

6.2 - If the spill is still fresh, soak up as much of it as you can with a paper towel but avoiding to rub it deeper into the slate.

6.3 - Completely cover the stained area with about 1/2-inch thickness of cat litter—clay-based litter is best since it absorbs faster.

6.4 - If the affected area is small, you'll only need to let it sit for maybe half an hour. For a large stain, leave it overnight.

6.5 - Sweep up the kitty litter from the floor and scrape off the remnants with a wood scraper

6.6 - Scrub the stain clean with a bristle brush and a mild detergent.

6.7 - Rinse the area thoroughly with clean, warm water and wipe it dry with a clean cloth.

There are also other absorbent materials that you can try out, such as baking soda or corn flour. If you try baking soda, make a paste by mixing it with water and applying it to the affected area.

Once the mixture has completely dried, scrape it off the floor using a wooden or plastic scraper. You can then wash the surface with a mild detergent mix before rinsing it with warm water and drying it off with a clean cloth.

7 - Mineral Spirits

Used mainly for thinning and cleaning oil-based paints, stains, and varnishes, mineral spirits is a clear product without any additives that can be very effective at cleaning up oil stains and spills.

7.1 - You just need to pour the mineral spirits directly onto the stained area and leave it to sit for a half hour.

7.2 - You can then scrub the area with a bristle brush to bring out the oil and stains.

7.3 - Soak up the mineral spirits and the dirt with paper towels.

7.4 - Finish up by washing the area with a mild detergent solution and then rinsing it thoroughly with warm water and a clean cloth. Dry the surface with a clean cloth.

Products to Avoid When Dealing With Stubborn Stains

After you're done scrubbing the floor, you might notice some stain spots here and there on the floor surface resulting from spills or other mishaps from various substances.

Either long-term or recent, there are a few techniques that can be used to try and remove them. There are, however, certain products that you must stay away from that are not compatible with slate.

Acidic Cleaners

Acidic cleaners, even natural products such as vinegar or lemon juice, will likely etch and damaged the slate and should be avoided.

Oil Based Cleaners

Oil-based cleaners used to remove stains could clog up the textured surface of the slate, and leave the scrubbed area slippery. It could also alter the way your slate accepts the sealer treatment, leaving the final coat with a blotchy uneven sheen.

Abrasive Cleaners

Abrasive cleaners are exactly what they're called: abrasive. This means that instead of dissolving or absorbing a stain, they will actually remove a layer of material from the floor surface.

Some abrasive cleaners are very strong chemicals that can be extremely invasive and damage the slate and the grout. They will likely also remove the sealed coating from that area, exposing the slate to liquids and stains.

For more information on how to give proper care to your slate flooring and for other tips, you can check out several of our pieces about "How to Care For Slate Tile Floors," "How to Reseal Natural Slate Flooring," and "Cleaning the Grout of Slate Flooring."