Final answer:
Hard gel, also known as traditional gel nail polish, must be soaked off using acetone. Nail technicians need proper training and certification.
Step-by-step explanation:
The type of nail gel that requires being soaked off with acetone is called "hard gel" or "traditional gel nail polish". Acetone is a powerful solvent used to dissolve these types of nail gels, which do not come off with regular nail polish remover. Nail technicians are trained in the safe and effective removal of these durable gel polishes.
Professional nail technicians should undergo proper training and obtain certification to ensure they are skilled in application and removal techniques, as well as knowledgeable about hygiene and safety practices. This helps to mitigate health risks associated with professional manicures and pedicures, such as infections and exposure to harmful chemicals.