The Thompson’s WaterSeal Clear Waterproofer is an extremely strong product. For use only on porous surfaces, the waterproofer is made up of hydrocarbon resins and polyoxyaluminum distearate in aliphatic hydrocarbon (mineral) spirit. The jargon aside, the solution claims to work well to protect wood, concrete, and brick against the most severe weather conditions.
Despite its strength it is not a good choice for most projects. Rarely does anyone need that level of strength and coverage, and most penetrating sealers (especially if you purchase a concentrated variety you can dilute yourself) will be just as effective. However, this Thompson’s WaterSeal offering is a good choice if you happen to live on top of a mountain, or on a storm-ridden beach front with heavy rains and driving winds.
The product itself is actually fairly dangerous to apply. You must apply the sealer in a well-ventilated area that has no flammable materials or things capable of producing sparks nearby. One spark could potentially light the entire project into flames. Similarly, the fumes can be extremely hazardous to your health, requiring application ideally outdoors. It would not be wise to use this sealer in a basement or even a garage, depending on the ventilation situation.
The product has an extremely high VOC content, making it a bad choice for states like California, New Jersey, New York, and others with strict environmental regulations. It is also not the best choice if you yourself care about the environment. If you do decide to use this product, make sure to take extreme care in its application and storage.