Video Guide
Introduction
Cleaning Cast Stone ensures it stays looking as fabulous as the day it was installed. At the same time, effective Cast Stone maintenance provides long-lasting protection.
It’s a question we’re often asked. How do I keep my cast stone looking as good as when it was first installed? Staining from whatever source can easily compromise the appearance of cast stone. And while weathering and aging is a feature than many people look for, others value the original colour and pristine appearance of cast stone.
The benefits of keeping your cast stone clean:
- Keeping that ‘wow’ factor.
- Remove Dirt and Grime
- Protect the Surface
- Enhance Longevity
So, in answer to this common question, here’s our complete guide to cleaning cast stone and effective cast stone maintenance. You’ll find that following these simple processes is straightforward and will refresh the appearance of your cast stone.
Principles of Cleaning Cast Stone
But before we take a good look at the different methods of cleaning cast stone, it’s important to remember a few key principles. They’re an investment in quality, so really worth knowing.
The first of these principles is to know that cast stone behaves similarly to natural stone. This means that any cleaning can expose the underlying cast stone, which may have weathered differently, causing subtle changes in colour. There’s no need to worry, though; cleaning gently will remove this issue.
It’s also important to remember that although cast stone may get dirty, this is usually unlikely to cause any particular problems. The only exception is if dirt is causing decay to the surface or staining the underlying stone, especially at street level. Should this have happened, it may be appropriate to arrange some remedial action.
Finally, we always recommend testing cleaning cast stone on a small area. This entails testing your cleaning method out on a small, inconspicuous area before continuing to clean any visible areas.
To summarise the principles of cleaning cast stone:
- Cast stone behaves like natural stone
- Dirt is not always harmful
- Always test first
All of this being understood, we can now take a closer look at the different methods of cleaning cast stone and effective cast stone maintenance.
Common Mistakes When Cleaning Cast Stone
| Common Mistakes When Cleaning Cast Stone | |
| Using High-Pressure Jet Washers | Using high-pressure jet washers can actually risk damaging the cast stone. |
| Scrubbing Cast Stone with Metal Brushes | Similarly, using metal or wire brushes can damage cast stone. These types of brushes are too abrasive and can scratch or permanently mark the surface. |
| Using Strong Acids Without Dilution | Some people assume that stronger chemicals will produce faster or better cleaning results. However, using strong acids without proper dilution can cause serious damage to cast stone. |
| Cleaning Large Areas of Cast Stone at Once | Another common mistake is attempting to clean large areas of cast stone all at the same time. When cleaning solutions are applied to multiple units simultaneously, they may remain on the surface for too long before being rinsed away. This can increase the risk of staining or surface damage. |
Common Cast Stone Cleaning Methods
Dry Brushing Cast Stone
First, let’s take a look at dry brushing cast stone. For the dry brushing cast stone cleaning process, you’ll need either a stiff bristle or a fibreglass brush. Brush the cast stone to remove any light deposits, such as mortar. It’s never a good idea to use scrapers, or metallic or wire brushes. That’s because they will mark the face of the cast stone, and this damage will be permanent.
Water Washing Cast Stone
Next up, let’s look at water washing cast stone. Because most dirt is water-soluble, cast stone cleaning with water is a popular option. Water washing is also a very simple process. That’s because all you need is a bucket, a brush, and a low-pressure hosepipe.
High-pressure hoses or jet washes should not be used for cleaning cast stone, as it can result in damage to the fine surface of the cast stone units or the mortar joints. For more stubborn stains, use a mild detergent like sugar soap. You can add this to the water before making sure it is thoroughly rinsed off. A note of caution: avoid saturating the cast stone because it can become stained as the dirty water dries off. Another issue of high saturation is the efflorescence that can occur as soluble salt in both the cast stone and mortar joints is reactivated by water. So, care is required. Just remember the mantra: no saturation.
Using Chemical Cleaners
Chemical cleaning has always been one of the most popular methods for cleaning cast stone. You can use hydrochloric acid – or indeed any of several easily available proprietary cleaners – to remove salt deposits, mortar stains and lime blooms. To get the right mix, simply dilute the hydrochloric acid in water to no more than 10% of the volume. We always recommend you use proprietary cleaners in accordance with the manufacturer’s instructions.
Care should always be taken when using chemical cleaners. That’s because chemical cleaners can, in some cases, change both the colour and the texture of the cast stone. As a result, we recommend that whole stones and all adjacent areas be treated to maintain a uniform appearance. Also, for effective cleaning and to prevent burning of the surface, the cast stone and surrounding surfaces – especially below where you’re cleaning – should be wetted with water before you apply any acid-based cleaning fluids. That’s because cast stone will always absorb a small amount of liquid, so it’s essential to wet the stone first.
Preparing & Finishing Cast Stone for Cleaning
Whichever method of cleaning cast stone you choose, prepping before you start and finishing with a few key processes at the end of cleaning will help provide the best results.
Before Starting
Remove moss, lichen and built-up dirt with a dry sponge or a soft-bristle brush. Always take great care not to cause damage to the surface of the cast stone by rubbing too harshly. Be sure to protect the area you’re working in with plastic sheeting or similar. Remember to wet first with lots of water but avoid over-saturating.
Next, it’s time for cleaning using your preferred method from those described above. Often, this will be enough to improve the appearance of your cast stone, especially with newer designs or those that have not been exposed to months of harsh weather. The cast stone must be cleaned individually; attempting to clean multiple units may cause acids or other cleaning materials to be left for longer than needed, which may result in damage to the surface of the cast stone.
After Cleaning
Leave to dry and check results. If the stain has not completely disappeared and the surface of the stone still feels smooth and not gritty, then a further application is ok. Once satisfied with the results, clean the whole unit. Remember to rinse after using plenty of water. Clean and remove from the area any excess liquid by using absorbent granules. Cleaning
Keeping Your Stone Looking Like New, For Longer
If you would like your cast stone to look like new for much longer, you could seal the stone after installation with a proprietary stone sealer, which would also seal the mortar joints as well. The product we recommend is called Lithofin Stain Stop. Find out more here.
Conclusion
Cleaning cast stone doesn’t have to be complicated. By using gentle methods such as dry brushing or low-pressure water washing, most dirt and stains can be removed without damaging the surface. When stronger cleaning is required, chemical cleaners can be effective if used carefully and according to instructions. Always test any cleaning method on a small, inconspicuous area first and avoid harsh tools or high-pressure washing.
Taking time to prepare the surface and rinse thoroughly afterwards will also improve results. With the right care and occasional maintenance, cast stone can retain its appearance and continue to enhance the character of a building for many years.
If you’d like any specific advice about any aspect of cast stone maintenance, please do feel free to call us on 01773 540704 or email our expert team at info@acanthuscaststone.co.uk
In the meantime, happy cast stone cleaning, and we hope you’ll be delighted with the results.
