In the earlier days of pool construction, plaster used to be a long-lasting, durable product primarily because it was made with white silica sand (mined out of California). Silica sand is made up of broken down quartz crystals. Over the years, and through the elemental transition with water and wind, quartz is broken down into tiny granules, leaving silicon dioxide (SiO2) or silica sand. These granules were used in the original plaster formula, increasing the product’s lifespan. However, when they could no longer mine silica in California, a decision was made to substitute the silica sand with white marble instead. Plaster was never the same.
We are often asked about sealing natural products outside. We never recommend sealing outside for a variety of reasons. Below is why we recommend against sealing and the disadvantages of it.
Stone sealers can change the look of the stone. If it’s the wrong kind of sealer, it can ruin the stone all together. If the sealer traps moisture, then the natural stone is not allowed to breathe as is needed which will cause issues in the long run.
Second, being an outdoor application, the UV rays from the sun have a huge diminishing effect on the effectiveness. So, areas will start to weather differently. Those in full sun may last 12-18 months whereas areas in the shade may last up to twice as long. Therefore, once you begin sealing the stone, you have to continue doing it.