Porcelain is generally considered safer than purple clay when it comes to pottery and ceramics. Porcelain is a type of ceramic that is known for its high firing temperature, which results in a hard, durable, and non-porous material. This non-porous nature makes porcelain ideal for food and drink containers, as it prevents the leaching of harmful substances into the contents. On the other hand, purple clay, also known as yixing clay, is a type of earthenware that is porous and can absorb flavors and odors over time. While purple clay is often used for tea pots, its porosity can lead to the absorption of chemicals and flavors, which may not be safe for long-term use.

The safety of porcelain is supported by various studies and regulations. For instance, the U.S. Food and Drug Administration (FDA) has established guidelines for the migration of heavy metals and other harmful substances from ceramic ware into food. Porcelain products that meet these guidelines are deemed safe for food contact. In contrast, purple clay products may not meet the same standards due to their porosity, which can allow for the migration of substances over time.

A study published in the Journal of Analytical Toxicology found that porcelain ware had significantly lower levels of lead and cadmium migration compared to earthenware, including purple clay. The study concluded that porcelain is a safer choice for food and drink containers due to its lower potential for leaching harmful substances. Additionally, the FDA has conducted numerous tests on porcelain products and has consistently found them to be safe for food contact.

In summary, porcelain is safer than purple clay due to its non-porous nature, which reduces the risk of leaching harmful substances. The FDA's guidelines and studies have further supported the safety of porcelain for food and drink containers, making it the preferred choice for those concerned about the potential health risks associated with ceramic ware.