This is the perfect phosphor set for small altars. Phosphorus without a protective coating on the surface will oxidize in about 6 years and the phosphorus will get dark stained. This product is coated with a clear coating to prevent oxidation. There is no need to worry about darkening as long as the paint does not come off. There may be marks like scratches caused by polishing, black spots or unevenness derived from the material. These are sold as shippable items and are not eligible for returns