(Block paving, Pattern imprint concrete, flags etc...)
Solvent or Oil based v's Water Based
One of the main things to consider when deciding which sealer to use on your paving is what you what the final look to be.
The main difference between these 2 types of sealer are the finish they will leave, the Solvent based sealer will enhance the colour and leave the paving looking like it does when it is wet, whereas the water based sealer won't enhance the colour (at least not as much as the solvent based) and leave the paving looking more like it does when it is dry.
A question we get asked a lot is which is better Solvent or Water based, my response is always the same, it all depend on how you want the finished paving to look, long gone are the days where Water based sealer were nothing more than a modified PVA, now a days Water based sealers are just as durable as their solvent based counterparts.
Acrylic v's Urethane (polyurethane)
For the purpose of this section when I refer to Acrylic and Urethane I am discussing the Solvent type of sealer, also I am using the terms Acrylic and Urethane as a generalisation, there are many, many different grades and types of each of these resins, the old adage, you get what you pay for some what applies with sealers, to get a better quality sealer you need to purchase a sealer made with higher quality grades of resin which cost more, cheap sealers from a hardware store, eBay and Amazon generally use low quality grades of resin.
Both these sealers will give you a colour enhancing look and come in a range of finishes from Matt to high gloss (Im not a huge fan of the term "wet look" as to me this can be an ambiguous term).
Both of these sealers have been used for 40+ years to seal external paving but there are some advantages and dis advantages of both.
Acrylic sealer
These sealers are the easiest to apply and are more forgiving if anything goes wrong (most problems such as blooming (I will discuss this further in later in this post) can be put right with an application of solvent) but generally won't last as long as a Urethane sealer (good ones at least) but when it does need to be resealed you can simply jet wash the surface and reapply the sealer.
Urethane sealer
As I have mentioned above a Urethane sealer, a good quality one at least, will last longer than most Acrylics before they require resealing, but mainly because of this they can be more problematic, you need to ensure that the surface is 100% dry and that there will be no rain for several hours after applying.
Even though they last longer, at some point they will require re sealing but with a Urethane the old sealer must be completely stripped off before you can apply a fresh coat of sealer (same applies if you get issues with blooming).
Efflorescence
One of the biggest myths about sealing concrete, especially block paving, is that you have to leave concrete paving X months before you can apply a sealer to allow the efflorescence out of the paving. This is completely false.
Efflorescence are white deposits cause by lime and calcites in the cement which can be unsightly, however if there is no efflorescence on the surface you are perfectly fine to seal to seal the paving as soon as it laid, the sealer will act as a barrier and stop the efflorescence from coming to the surface (I personally have sealed hundreds of drives as soon as they have been laid and never once had any problems with efflorescence later).
I believe the start of this myth is due to Block paving fitters not wanting to seal paving so came up with an excuse so they didn't have to.
Blooming
By far the most common question/issue we get asked about is about blooming, blooming is a frosted/white appearance in the sealer which is cause by moisture being present when the sealer is curing, this is usually situated in and around the joints but can affect the whole area if the the paving is damp.
Blooming will only occur with Solvent/oil based sealers as oil and water do not mix.
Blooming is formed as the water reacts with the solvent in the sealer and creates microscopic bubbles which get trapped in the sealer, with an Acrylic sealer this is very easy to rectify by applying a light coat of solvent to the dry surface, if however you get blooming in a Urethane sealer the sealer has to be removed and reapplied.
Low slip/anti slip additives
Depending on the surface being sealed Low slip is more or less important. Block paving and standard (council) flags are usually fine without low slip as the texture of the paving is quite rough anyway, however on Imprinted concrete the finished surface is fairly smooth and as such can be quite slippery when freshly sealed when wet.
As a bit of a side note all paving can be a bit slippery when it is first sealed, when freshly sealed water will bead on the surface (like a newly waxed car), this standing water is what can make the paving slippy, however like a waxed car, when the sealer weathers in a bit it the water will stop beading and drain off normally, this will greatly improve the traction of the surface.
Myths and Misconceptions
There is a lot of misinformation regarding the application of sealers, I will go through a few of the main ones here but I will be doing a more comprehensive list in another post.
Myth Number 1.
You have to leave Block paving X months before you can seal it.
I believe the origins of this myth come from paving fitters not wanting to seal paving. We commonly hear from customers, Joe Bloggs who laid the block paving told us we have to leave it 6 month before sealing it to let the efflorescence out.
The truth is you can seal paving as soon as it is laid, if you apply a sealer it will stop the efflorescence from coming to the surface. All concrete contain salts but fitters seal imprinted concrete after a few days of installing so why treat one type of concrete differently than another?
Myth number 2.
You have to use a colour when resealing Imprinted concrete.
This is another very common misconception we get asked about.
When the paving is dry and the sealer wears off, it looks completely different to the areas that still have sealer on them, however, 99% of the time this is just because the sealer has worn off, you need to ignore how the paving looks when it is dry and focus on how it looks when it is wet as this is how it will look with a fresh coat of clear sealer.
Myth number 3.
Solvent based sealer is better than Water based.
This myth stems back 15-20 years to when Water based sealers were nothing more than PVA thinned down. These days the technology of water based sealers has moved on significantly, so the 2 can perform very similarly in terms of longevity as long as the water based sealer is a good quality.
Breathable/Impregnators.
A couple of terms we are hearing a lot at the moment are Breathable and Impregnator.
We get a lot of questions asking if our sealers are impregnators or sit on the surface (topical), my answer to this is that topical sealers haven't really been used for over 10 years, it is an outdated technology, all sealers these day impregnate in to the surface to one degree or an other.
We also get asked a lot about whether a sealer is breathable, the question I ask back is why does it need to breathe? My opinion when sealing paving is that there is no reason why it would need to breathe, breathable coatings allow moisture to travel up through the paving, the problem with this is that it will also allow efflorescence to travel through the paving and become visible on the surface.
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