How To Clean Sandstone
There are a few good methods to clean sandstone and a couple of ways to avoid. First, you must decide whether you want your sandstone to be nice and clean or to age and look old and natural. If you are looking for old and natural, then the good news is you do not have to do a thing. If you are after a clean, look then please continue reading.
The method below will only work on organic stains such as tannin, leaf stains, animal droppings, food and wine stains, mould and algae. This method is for exterior surfaces only.
Things to avoid:
Do not use acid on natural stone. There are times when it might be necessary for a professional stone cleaner to use specific types of acid, but it is best left to them.
Do not use a pressure washer on Australian sandstone. High pressure water blasters can permanently damage the surface of the stone.
This is the method most tradespeople will choose to clean organic stains on natural sandstone. You will need a watering can, a broom and liquid pool chlorine (available from most hardware and service stations).
Step 1: Hose off any loose dirt and leaves.
Step 2: In a watering can, mix 5 parts water with 1 part liquid pool chlorine.
Step 3: Pour the watering can mix over the stone and leave it for around 10 minutes. Make sure the mix does not dry on the stone. Feel free to add more cleaner or mist some water on the stone if it is starting to dry.
Step 4: Use the broom to agitate the wet stone surface and then hose off the stone with clean water.
This will usually clean off most stains, mould and algae. If you have stubborn or old stains, then feel free to repeat the steps again. If necessary, you can leave the chlorine on the stone for longer periods of time, as long as you are keeping the surface wet with either a mist of water or more chlorine mix to stop it from drying. This will give the chlorine more time to work on the stains.
Using commercial cleaners
There are many great cleaners ideal for sandstone on the Australian market. Feel free to use these, but make sure you check that they do not contain any acids.
I have used and recommend Stain-Proof Alkaline Cleaner, this is an easy to use environmentally friendly chemical that works well over time.
These cleaning and sealing manufacturers have a range of cleaning products that I would not hesitate to recommend:
To seal or not to seal
If you want the stone to keep the clean look, then you should consider sealing sandstone. This will make it easier to clean in the future and stop stains from penetrating deep into the stone. Sealing will also reduce the amount of water that the sandstone absorbs, limiting algae and moss growth.
The above linked companies also make some great sealants, but here are a few tips.
- A surface sealant is almost never recommended. An impregnating or penetrating sealant works best and allows the stone to breathe.
- Never use a cheap sealant from a hardware. They do not last as long and can change the look of the stone.
- If you are considering using an enhancing or wet look sealant, do some test samples first with both light and dark samples of the stone. These types of sealants have mixed results on sandstone and they are much harder to remove after application.