Question:

For gold foil stamping on black cardstock, if the customer notices mottled black spots on the printed surface, what is the most likely cause?

A. Poor quality of the hot stamping foil, leading to color differences between batches

B. Excessive stamping pressure, causing the top layer of the foil to peel off

C. Acidic substances inside the black cardstock seep out, causing oxidation of the foil

D. Excessively high stamping temperature, burning the foil during the process

Answer: C

Explanation:

The metal coating on hot stamping foil is very thin, and black cardstock is naturally acidic.

After being stored for a period of time, the acidic substances inside the paper slowly seep out and corrode the metal layer of the foil, resulting in mottled black spots.

Prevention Solutions:

1. Use acid-free black cardstock

2. Pair with oxidation-resistant hot stamping foil

3. Store finished products in a dry and well-ventilated environment

Note:

Oxidized black spots are irreversible, and the product must be scrapped.