| Surface Imperfections (Glass On Surface, Mineral Bloom) | |
| Possible Cause | Suggested Remedy |
| Melt temperature too low | Increase melt temperature |
| Mould temperature too cold | Increase mould temperature |
| Insufficient packing pressure | Increase packing pressure |
| Injection rate too slow | a. Increase first stage pressure b. Increase boost time c. Increase injection speed |
| Insufficient material in mould | a. Increase shot size and maintain constant cushion b. Inspect non-return valve for wear c. Decrease injection transfer position (thereby increasing the peak pressure) |
| Water on mould surface | a. Increase mould temperature b. Repair any water leaks |
| Excessive lubricant on mould | a. Clean mould surface with solvent b. Use mould release sparingly |
| Moisture in material | a. Review material handling to eliminate moisture pick up b. Dry material prior to moulding c. Use hopper dryers |
| Insufficient venting | Provide adequate vents |