Formation Summary

1. More uniform formation is obtained with a new wire than an old wire presumably due to fewer large scale formation defects such as streaks.
2. Mechanical entanglement and electrochemical forces cause flocculation but there is no conclusive evidence as to which one governs or if the factors that directly affect them are even known.
3. The more uniform the stock, the better the formation.
4. Short, well-refined pulps contributes favorably to formation.
5. Entrained air in the stock at the slice is deleterious to good formation.
6. The hydrodynamics of the distribution system and headbox must be well controlled to insure a uniform product. This flow should be of small scale but high intensity turbulence.
7. The distance of perforated rolls from the slice is critical to good formation. Also, a balance between the flocculation tendencies and turbulence generating characteristics of perforated rolls must be maintained.
8. The angle of impingement onto the forming fabric should be as flat as possible for good formation.
When low headbox consistencies must be used, a steeper angle is needed to drain excess water at the breast roll. In any event, any breast roll discharge will tend to hurt formation.
9. If a breast roll discharge is taken, it should never be greater than that which can escape between the breast roll and the forming board. Care must be taken to avoid “double forming” when using a breast roll discharge.
10. Both the dandy roll and shake are beneficial to formation but their effects are not additive.
11. There is some evidence to indicate that the shake intensity (amplitude*frequency2) is the important parameter when considering shake.