Considering getting concrete worktops but have no clue about the maintenance? This
can all depend on the type of sealer you use. The type of sealer should be chosen to
suit the finish of the concrete.
Some sealers do not adhere properly to a highly polished concrete worktop, and some
sealers won’t do the job adequately if there is too much texture. Also, some require you to
have them resealed every year or few years, whilst some last the life of the concrete – but
most are somewhere in between.
But that’s not all, your choice of sealer should also depend on how you would like the finish
of the surface, as there are options such as colour enhancing, matt, glossy, and satin.
What is Sealer?
Why does all this matter? If you have a basic understanding of what sealer is, and how it
works, you can easily get to grips with the differences in the types of sealer, and how they
can affect the maintenance.
At the very least, sealer is made up of two parts – the plastic component called a resin, and
a carrier. Most sealers are water-based, meaning the carrier is water, or solvent based. The
cool part – the carrier ‘carries’ the resin onto or into the concrete, and then will evaporate and
just leave the resin to protect the concrete.
Types of Sealers and Its Properties
Concrete worktops are generally sealed using one of the following 3 methods:
- Simple penetrating sealer with wax
This is the most basic type of sealer for concrete, the easiest to apply and the most natural looking. Penetrating sealers are usually clear with a water like consistency and are very easily applied. The surface is initially wiped down, then the sealer is generously applied using a wet cloth and worked into the concrete to deeply penetrate the surface. Multiple applications can be preformed and you can also give a few coats of wax (such as beeswax or Carnauba wax) to further enhance the polished finish.
Some penetrating sealers will enhance the surface colours to produce a more vibrant tone similar to oiling a top. Others will be completely invisible for a true raw concrete look. Both these finishes will perform much the same way – they will repel liquids for a short amount of time before staining occurs. Penetrating sealers do not have any resistance to acidic substances such as vinegar or lemon juice. However, when marks do occur, they will slowly fade and blend to from a nice aging patina.
Penetrating sealers and wax are the most popular finishes due to the easy maintenance and natural finish.
- Reactive densifying sealers
This is the most popular type of sealer used by Fluid Stone Studio. The concrete is polished, or acid etched to the desired sheen level. Then the sealer is applied very similarly to the penetrating sealer method. We make multiple applications of a primer which is water based and uses either nano sized lithium or sodium particles. These soak deep into the concrete pores and cause secondary reactions with the ‘free lime’ which is a natural by-product of the initial cement hardening phase. This secondary chemical reaction is known as CSH – Calcium Silicate Hydrate.
These are glass like crystals (which are actually harder than the concrete itself) will form and grow into the pores of the concrete and effectively make the concrete less porous. Multiple applications are made until the surface is deeply saturated. Then a final few coats of a nano acrylic modified sealer are then applied. This sealer is also reactive and will form a combination of acrylic and CSH on the surface of the concrete to a very durable soft sheen to the concrete.
The advantages of these type of sealer are:
- It will allow the concrete to breathe as it is not actually coated with anything – rather it is treated using covalent chemical bonds rather than an adhesive bond. This means there is nothing to peel off like a plastic topical sealer can.
- It is water based and very easy to apply and re-apply if ever needed due to heavy WEAR AND TEAR.
- It is very scratch proof compared to a coating, it is also very heat tolerant, Hot pans are fine to place on the tops although it’s always best to use trivets and chopping boards to avoid unnecessary wear.
- Above all else, with natural sealers such as reactive or penetrating, the surface still feels like raw bare polished concrete rather than a piece of plastic and to us this is the most important features when having concrete in the home. The first thing people do when they see a concrete top is run their hands along it to feels its desirable tactile nature.
- Topical sealers
Topical sealers are popular in the US they are more stain resistant than treating the concrete, but they also require more care when applying to achieve a professional finish.
The other downside is they are all basically just a thin plastic coating which will eventually wear, possibly peel and certainly need re-sealing at some point. There are 3 main types of topical sealer commonly used on concrete worktops:
- Acrylic Sealer
Acrylics are the thinnest of the topical sealers. They are easy to apply using a short nap roller and they also soak well into the concrete. As they are the thinnest topical sealer, they are the most natural looking finish with various options of high gloss, matte and colour enhancing. The only draw back with acrylics is due to their thin natural looking finish, they also need to be re-sealed more often and the surface will wear quicker, typically these would need re-sealing every couple of years.
- Polyurethane Sealer
This type of sealer is very hard and is also more scratch and chemical resistant than acrylics. Like other sealers, there are some options available for polyurethanes, polished high sheen and matte. It can come as a single component air drying finish using water or solvent as its ‘carrier’ and can also come as a more professional 2 part chemical curing versions using a ‘hardener’ which is mixed in with the sealer before applying. Polyurethanes are a tricker to apply and they do not lay down as nicely as an acrylic. The finished surface may have to be lightly sanded down to remove roller marks and any dust particles which may have landed on the top.
Once installed, Polyurethanes do change the look of concrete more than an acrylic, as they are thicker they will feel more like a coated / varnished surface compared to a natural finish.
Although this finish is one of the hardest available and often described as very scratch resistant it does not mean it will not get scratched. Polyurethanes are still basically just a thin plastic coating and certainly nowhere near as hard as steel or ceramic. In fact if you were to slide ceramic cups and plates over the tops or use as a chopping board they will get scratched pretty easily. However, if you use the tops a bit more carefully the sealer will last many years before needing to be re-sealed.
Epoxy sealers can be water based, solvent based, or 100% solids – meaning they have no
carrier that has to evaporate. They also have the choice to be colour enhancing.
One of the advantages of using epoxy resin is that it is thicker than all the other types of sealers. If you have any unwanted texture or porosity from badly formed concrete, the epoxy will fill this in and make it smooth to touch. If you have inherited a top when moving into a new property. You will not know the quality of the concrete used. If it looks shabby with rough texture and visible air pockets on the top surface, then epoxy may be the best choice for repairing and resealing.
Due to the thickness of the epoxy coating, it is usually good to last the life of the concrete,
and it has a heat resistance of just over 200 Celsius. However, it is worth noting that all epoxies do yellow from UV exposure over time and due to the extra thickness, epoxies are also the most plastic feeling out of all the sealers available. Epoxy is not as hard as polyurethane sealer, so it may need re-sealing as time passes to cover any scratches or scuffs on the surface. This would be done by sanding the worktop and applying another coat with a roller. With 100% ] solids epoxy, you have many different options. It can be built very thick to provide an ultra-glossy surface and you can also add pigments or metallic powders to make colours and faux stone effects. Of course, ‘faux’ always looks a bit fake if it’s not done professionally, which is really the main drawback of this type of sealer. Skilled professionals will use sophisticated spraying equipment to achieve a perfect workshop finish, but when the worktop is used in a busy kitchen and needs to be re-sealed. It’s very hard to replicate the original quality with a roller.
As you can tell from our article Fluid Stone prefer to take a purist approach to sealing concrete.
Something which preserves the natural beauty of concrete – something that ages with grace. It is widely accepted that raw natural concrete should not really be sealed with a plastic coating. It should be left to breathe and patina with each mark being treasured as a moment in time… Like the Japanese philosophy of Wabi Sabi:
“Taken from the Japanese words wabi, which translates to ‘less is more’, and sabi, which means ‘attentive melancholy’, wabi sabi refers to an awareness of the transient nature of earthly things and a corresponding pleasure in the things that bear the mark of this impermanence. As much a state of mind—an awareness of the things around us and an acceptance of our surroundings—as it is a design style, wabi sabi begs us to appreciate the simple beauty in life—a chipped vase, a quiet rainy day, the impermanence of all things. Presenting itself as an alternative to today’s fast-paced, mass-produced, neon-lighted world, wabi sabi reminds us to slow down and take comfort in the simple, natural beauty around us”.