Solvent-based sealers are widely used for outdoor concrete surfaces, which help to augment the color of the concrete and also protect the surface. In a solvent-based concrete sealer, unlike the water-based ones, the polymers do not exist as separate particles. The solvent and the polymer are mixed for a clear and continuous solution.
As the solvent evaporates from the sealer, the polymer chains get closer and they become intertwined eventually.
The concrete surface that has been sealed using a water- or solvent-based sealer appears glossy because, in both sealers, the polymer stays on the surface of the concrete. In the case of a solvent-based sealer, it wets the concrete surface and penetrates deeply into the surface and so the result is a glossier finish, which augments the color of the concrete below.
Solvent-based concrete sealers act as a protective top coat for the concrete surfaces and offer stain and chemical resistance. They are UV resistant, non-yellowing, and are available in various sheen levels. A solvent-based sealer has a greater penetration ability into the concrete as compared to a water-based sealer.
However, solvent-based sealers have a few drawbacks. These sealers have higher VOC content and are considered to be less environmentally friendly. Also, they are not recommended for use on interior surfaces and areas that have poor ventilation. Solvent-based sealers are not as cost-effective as the water-based ones.
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The uses of solvent-based sealers include:
Solvent-based concrete sealers can be applied using airless or LPHV (low-pressure, high volume) sprayers or roller brushes. Low-pressure or pump-up sprayers are suitable for solvent-based sealers containing less than 35% solid content. Sealers containing more than 35% solids can be applied by using a lamb wool applicator, which is essentially a wool rag that is wrapped around a block of wood.
Avoid applying the solvent-based concrete sealer on rainy, humid, or foggy days. If it is very hot, then the application should be done during the cooler hours and when the concrete surface is in non-direct sunlight or shade. Ensure that the surface is free of moisture and completely dry, otherwise, it will interfere with the bonding and curing.
The sealer should be applied according to the coverage rate recommended by the manufacturer and you must not over apply the sealer. Over-application or too many coats of the sealer can cause the sealer to peel, bubble, and turn white.
Frequently Asked Questions
Can you use a water based sealer over a solvent based sealer?
If you are looking for a short answer, that would be ‘no’. If you are looking to use a seal over a previous work that has been done, it is important to ascertain what kind of sealer was used in the first place. If a water-based sealer was used in the first instance, the rules are far more relaxed. You can reseal the existing layer using either a water-based sealer or a solvent-based sealer, it will not make a difference. However, if you apply a water-based sealer on top of a solvent-based sealer, it will not have the desired effect and you will end up taking the protective layer away from the concrete. You can only reseal a solvent-based sealer with another layer of solvent-based sealer.
If you are not sure of what type of sealer was used the first time around, you can do a swatch testing. Pour a small drop of xylene onto a corner portion of the sealed paver and wait for approximately 15 seconds. When you wipe off the xylene, if the surface is tacky to the touch, the existing sealer is solvent based. If the surface is not feeling tacky, it means that the existing sealer is a water-based one.
How much solvent based sealer will I need?
Regardless of whether you are using a solvent-based sealer or a water-based sealer, it is important to determine how much you will need to buy. The coverage rates for sealers, both solvent based and water based, are determined by square footage. So, for instance, if the label at the back of the sealer you want to buy says it has a coverage rate of approximately 500 square feet per gallon, you will need to calculate the overall square footage of the area you want to seal and do the math. Putting this into a neat equation would look like this:
1,000 sq. ft. (example of total area needed to be covered)/500 sq. ft = 2 gallons of sealer
The math is not too complicated, regardless of how vast the area is. But it is recommended that you look around at deals before you purchase. For instance, if the sealer is available in pails of 5 gallons, but you only require 4 gallons, you should still consider buying the 5 whole gallons if that is coming out to be less expensive. Concrete sealers especially when required for large scale products, are not the cheapest items on the market. But before you make any decisions on which solvent-based sealer you want to buy, make sure to check the VOC (volatile organic compound) content in the product.
How long does solvent based sealer take to dry?
A solvent-based sealer typically takes less time than a water-based sealer to dry, but this will depend on a variety of factors, such as humidity, temperature, dew point, etc. Typically, a solvent-based concrete may dry to the touch between 1-3 hours from applying. If you are using a decorative sealer, it should not take as long to dry and the job should get done between 1-6 hours, depending on other factors like temperature and weather.
However, a penetrating concrete sealer is likely to take longer because they need to seep into the concrete and will dry from within, making their way to the outside. It can take anywhere between 2-8 hours since the sealer was applied, depending on the weather. A penetrating sealer will also require two coats, where the second coat is applied to the first one while it is still wet. This is important because if the second coat is applied on a dried sealer, the first one will repel the second coat, therefore, nullifying its effect. The second coat should, therefore, be applied anywhere between 1-15 minutes since the first coat was applied.
How long does solvent based sealer last on concrete?
Solvent-based concrete sealers typically last longer than water-based concrete sealers. If you are using a decorative solvent-based concrete sealer, it is likely to last anywhere between 6 months to 3 years. But to keep the look of the concrete as new as it was first laid down, you need to continue with the sealing at the required time.
If you are using a durable concrete sealer, it is important that you prep the surface before applying the sealer. You will need to grind the floor properly before using this type of coating or else the durability will reduce by a large margin. On an appropriately prepared concrete surface, durable sealers can last over a decade.
If you are looking at a penetrable option, it is meant to last you for the life of the concrete. Silicate-based densifiers, for instance, become stronger and make the concrete stronger as time passes. But the durability of even a penetrating sealer may depend on the UV exposure, water damage, traffic, etc. While penetrating sealers are usually water based, some may also be solvent based.
Can solvent based concrete sealer be removed?
Yes, a solvent-based concrete sealer can absolutely be removed. If you already know that the sealer you are dealing with is a solvent-based sealer, you can set about following these steps:
- If you see any visible peeling, get to that first by applying a solvent-based stripper, such as xylene, on those parts first.
- Once you have done that, apply the solvent-based stripper on the entire area where the sealer has been applied.
- Pressure wash that surface after some time and then allow it to dry completely.
WARNING: If you have treated the concrete with a dye or stain, xylene is likely to affect the color.
If by any chance, you are not sure of whether you are dealing with a solvent-based sealer or a water-based sealer, it is important to determine the type of sealer before you settle on a plan of action. While a solvent-based stripper is usually the method most professionals go with (since it is faster and more aggressive), you may have to decide on different methods on removing the sealer depending on the type of sealer you are working with.