There are several possible reasons for the depression that may occur after the epoxy resin crystal glue is cured

1. Bubbles: During the mixing and construction process, if the glue is not fully and evenly mixed, or the construction is uneven, the bubbles suspended in the mixture may not be completely expelled. Eventually, voids will form after drying, resulting in depressions.
2. Ambient temperature: The curing of epoxy resin crystal glue needs to be completed under certain temperature and humidity conditions. If the temperature is too low, the resin cannot flow sufficiently, and depressions are likely to occur.
3. Insufficient or excessive amount of hardener added: If the amount of hardener added is insufficient, the curing will not be complete. Conversely, if too much hardener is added, shrinkage will occur, also leading to depressions.
4. Improper substrate treatment: If the substrate is not thoroughly cleaned, cleared, or sanded before construction, it may cause poor adhesion and an uneven surface. As a result, depressions will form when the epoxy resin crystal glue is curing.

To avoid the occurrence of depressions, it is recommended to fully stir and mix during the construction process, and add the hardener correctly according to the usage instructions provided by the manufacturer. At the same time, pay attention to the construction ambient temperature and substrate treatment to ensure that the coating adheres well to the substrate and avoid problems such as depressions.