Advantages:
1) Bluestone is very porous, so stains are very difficult to remove. Sealing stone is highly recommended if people will be eating and drinking on it.
2) It gives the stone a "wet" look which some people prefer from an aesthetic perspective. The picture on the right shows a patio that is partially wet / partially dry and illustrates the two different looks.
3) While rare, it is possible for stone which is blue / gray when it is harvested to change color over time to full color range. This is due to minerals in the stone that oxidize when exposed to the air. Acid rain makes this process happen more quickly. Sealing the stone immediately upon installation can be helpful in preventing this change.
Disadvantage:
1) Sealant needs to be reapplied periodically, especially on areas which see heavy foot traffic
We don't have a particular product that we recommend, so test on a scrap piece before applying to the entire installation.