The following steps may be done during manufacturing in order to prevent Film Cracking (Type 1): I. Reduce processing temperatures to minimize core thermal expansion. II. Reduce drying conditions (or increase spray rate) so that some moisture retention in the coating occurs due to augment plasticization effects (thus increasing film flexibility) III. Improve drying (reduce spray rate or increase temperatures) to offset overwetting. IV. Increase pan speed to minimize dwell time in spray zone.

• A. All statements are correct
• B. Only ONE statement is correct
• C. Two statements are correct
• D. Three statements are correct

Answer: (C)

Film cracking happens when drying creates tensile stresses in the coating. The most effective way to prevent Type 1 cracking is to control the coating’s moisture content so it stays flexible during drying, and to limit how long the coating remains in the spray zone where moisture uptake can vary.

Moisture retention in the coating can act as a plasticizer, making the film more pliable as it dries. By reducing drying intensity or increasing spray rate, you slow down evaporation enough for some moisture to remain, which helps the film flex rather than crack as it cures. This targeted approach directly combats the brittleness that leads to cracks.

Increasing pan speed to shorten dwell time in the spray zone reduces the opportunity for the coating to absorb excess moisture and for uneven drying to develop. With less time in contact with spray moisture, the film forms more evenly and internal stresses are reduced, which lowers cracking risk.

Lowering processing temperatures to cut core thermal expansion sounds helpful, but it can have the opposite effect by slowing drying and trapping moisture, which can introduce other stresses and defects rather than reliably preventing cracks.

Drying more aggressively to offset overwetting can address surface wetness, but it often introduces other issues like rapid skin formation and differential shrinkage, so it’s not the most direct or consistent fix for Type 1 cracking.

So, the two approaches that best align with preventing Film Cracking Type 1 are promoting moisture-induced plasticization and reducing dwell time in the spray zone.