Cleaning Slate can present some difficult challenges due to its inherent characteristics,  the many different types of slate and also to the many different types of sealers use for sealing slate tiles.

It is important to test the slate surface before any cleaning procedure takes place.  It is important to understand what cleaning products without damaging the slate surface.  It is also important to understand what sealers were used on the slate before any cleaning process can take place.

Slate is a stone tile obtained from sedimentary deposits along river beds.  There are may types of slate tiles originating from many places around the world and the cleaning process can vary depending on the type of slate tile being cleaned.  Before cleaning slate you should test the slate surface to be sure that the cleaning product will not damage or discolor the slate surface.  Alkaline cleaning products are generally safe for cleaning slate but cleaning slate with acidic cleaning products could potentially damage the slate tile surface.

Slate is a porous stone tile and there are many different types of impregnating and topical sealers that are used to seal slate.  Generally if there was only an impregnating sealer used then the slate can be cleaned with normal tile and grout cleaning methods.  Slate can also be sealed with many different types of topical wax sealers.  If the slate tile appears to have a topical sealer on it then the sealer needs to be stripped off before any cleaning process can begin.  If a water based topical wax sealer was used then a water based floor strippers can be used to strip the wax from the slate.  It is important to understand that removing wax can be a difficult and time consuming process and should generally be done by a professional tile cleaning service.  If the slate was sealed with a different type of topical sealer then this type of sealer can be extremely difficult to clean by even a professional tile cleaning service.  In this case (mek) or commonly known as paint stripper will be needed  to strip the sealer off of the slate tiles.  You can test the slate tile surface for the type of topical sealer that was used by putting some acetone on the sealer.  If the topical sealer begins to emulsify then most likely a water based wax topical sealer was used.  If the acetone does not emulsify the topical sealer then some other type of sealer.  In this case it is best to contact a tile cleaning professional to address you slate tile stripping situation.

Assuming that there is no topical sealer on the slate tiles then cleaing them is similar to cleaning ceramic tiles.  The dirt, grease and grime on slate tiles is generally of an acidic nature.  An alkaline cleaning product made for tile, grout and stone is necessary to react with the acidic dirt and grim on the slate tiles to make them easier to clean.  An alkaline tile and stone cleaning product should always be used for your slate cleaning process.

Mix the alkaline cleaning product with the hottest tap water available in the ratio on the instructions of the cleaning product.  The hotter the temperature of your cleaning solution the better your cleaning results will be. 

Apply the alkaline cleaning solution liberally to the slate tile surface and allow it to dwell there for at least 20 minutes.  Due to most slate tiles being inherently porous it is important to let the cleaning solution dwell for as long as possible without drying on the surface.  You want the cleaning solution to get deep inside to pores of the slate tiles and emulsify any dirt and contaminates.

While the cleaning solution is dwelling on the slate tile surface you should agitate the tile with a soft brush or soft scrub pad.  Some types of slate can be scratched by aggressive scrub pads so test the slate surface beforehand to be sure your scrub pad will not damage the surface of the slate. Definitely do not use any type of steel wool or extremely abrasive pads when cleaning slate.  Slate stone surfaces can vary in hardness and you could potentially damage the surface with aggressive cleaning brushes or aggressive scrub pads.

You should generally scrub the slate surface until you are confident that all of the dirt, grease and grime and any other contaminates are emulsified from the slate surface.  Then you can rinse clean the slate tile surface with a mop or towel to insure that there is no remaining dirt or cleaning residue. 

After you have cleaned your slate tile surface you may notice that the grout is still not as clean as you had hoped for.  It may be necessary to do some extra scrubbing on the grout lines with your scrub pad.  Most slate tiles are indeed acid resistant so an acidic grout cleaner containing urea acid can be used to clean the grout.  Just be sure to test the acidic cleaner on the slate to be sure it will not damage or discolor the slate tile surface. You can read more about how to clean grout in our grout cleaning section here.