Coal Tar Asphalt Sealer has been in use many years and with overall great success. It does however has drawbacks which are mostly safety related. Coal Tar will burn you if you get it on your skin, and has possible cancer causing effects that science can back up.
Coal Tar can be sprayed or applied by brush or squeegee and offers excellent results depending on the amount of water mixed with the sealer. Mixing will generally be around 20%, 2 gallons of water to 8 gallons of sealer.
It is very important to wear protective clothing if applying coal tar to protect yourself from potential splashing and over-spray. It is the most widely used Asphalt Sealer in the United States currently because of it's availability.