Ceramic coffee mugs are among the most common vessels for enjoying a hot drink. They are made from clay that is shaped, fired, and then coated with a glaze to seal the surface and make it non-porous. That glaze is what gives a mug its smooth finish, color, and pattern. But glazes can also raise questions about lead, and everyday use calls for a few practical care habits to keep your mug in good shape and your drinks safe.
What to Know About Ceramic Glazes and Lead
Ceramic mugs get their glassy surface from a glaze that is fused to the clay body during firing. According to the U.S. Food and Drug Administration (FDA), lead may be present in the glazes or decorations covering the surface of some traditional pottery. If the pottery is not manufactured properly, this lead can leach into food and drink that is prepared, stored, or served in the dishes.
The FDA explains that traditional pottery and other ceramicware are often made from earthenware, a porous clay that must be glazed to hold liquid. The glaze may contain lead to help the glaze particles melt and fuse during firing. When the pottery is fired at the proper temperature for the proper amount of time, essentially all the lead is bound into the glaze and any migration to food is insignificant. However, if the firing is not done correctly, the lead may not fuse and can contaminate food.
The FDA also notes that some potters have switched to non-lead glazes but may still use old kilns that once fired lead-containing glazes. Lead residues in the kiln can unintentionally contaminate the new “lead free” pottery, and that lead may not fuse into the non-lead glaze, so it could leach into food. For a broader look at how ceramic compares with other materials, see our coffee mug materials guide.
The agency advises consumers to pay particular attention to certain “problem types” of ceramicware: items that are handmade with a crude appearance or irregular shape, antique, damaged or excessively worn, purchased from flea markets or street vendors, or those from an unknown manufacturer. Pottery that is brightly decorated in orange, red, or yellow is also flagged because lead is often used with these pigments to increase their intensity. The FDA states that pottery made in commercial factories for everyday use is much less likely to have problems related to lead.
If you are unsure about a piece, the FDA suggests looking for a warning label. Some pottery manufactured only for decoration may have a stamp on the bottom such as “Not for Food Use, May Poison Food.” Do not use items with this type of warning for cooking, serving, or storing food or drinks. The FDA also says that no amount of washing, boiling, or other process can remove lead from pottery.
Consumers can buy lead-checking kits at hardware stores or online. These kits typically include swabs that you rub on the food-contact surface; if leachable lead is present, the swab changes color. If a check shows leachable lead, the FDA strongly advises against using the pottery for food or drinks. If you cannot check the pottery or determine that it is from a reliable manufacturer, consider not using it for food.
Separately, the FDA notes in its general information on lead in food and foodwares that there are no federal regulations that authorize lead for use as a color additive or food additive, including as a component of foodware, cookware, or food contact surfaces. The agency monitors and regulates levels of lead in foods and can take action if a food is found to be unsafe.
Everyday Care for Stoneware and Ceramic Mugs
Ceramic mugs come in many types, including stoneware, porcelain, and earthenware. Each may have specific care requirements. As an example, CorningWare provides detailed use and care instructions for its stoneware Meal Mug. While these instructions apply to that specific product, they illustrate the kind of attention that helps any ceramic mug last longer. To explore the range of mug types, visit our mug types overview.
CorningWare’s guidance warns that all stoneware can break, and you can help prevent damage by following a few rules. When used near extreme heat, stoneware can break, so the company says not to use it on a stovetop, under a broiler, on a grill, or in a toaster oven. Rapid temperature changes are also a risk: do not transfer stoneware directly from the freezer to a hot oven, add liquid to hot stoneware, or place hot stoneware on a wet or cold surface. The safest place for hot stoneware to cool is on a cooling rack, dry potholder, or dry cloth.
For cleaning, CorningWare advises against soaking stoneware in water for an extended period and against using abrasive cleansers or abrasive scouring pads. Hard objects such as metal utensils can damage the surface. Instead, use non-abrasive cleansers and plastic or nylon cleaning pads. The Meal Mug is labeled as dishwasher safe, with the plastic lid placed on the top rack, but hand washing is also recommended. Before first use, wash stoneware and lids thoroughly.
These instructions are specific to CorningWare stoneware. Your own ceramic mug may have different recommendations. Always follow the care instructions that came with your mug. If you no longer have them, a good general approach is to avoid sudden temperature shocks, use gentle cleaning tools, and check whether the mug is marked as microwave or dishwasher safe. For more on care by material, see our care by material page.
Microwave Safety with Ceramic Mugs
Many ceramic mugs are labeled as microwave safe, but safe microwave use involves more than just the mug material. The FDA, which regulates microwave ovens, offers several tips for safe operation. One important caution concerns superheated water.
The FDA has received reports of serious skin burns or scalding injuries when hot water erupted out of a cup after being overheated in a microwave. Superheated water is water heated past its boiling temperature that does not appear to be boiling. This can happen when water is heated by itself in a clean cup. If superheating has occurred, a slight disturbance, such as picking up the cup or adding a spoonful of instant coffee, may cause a violent eruption, with boiling water exploding out of the cup.
To reduce this risk, the FDA says to add substances such as instant coffee or sugar before heating. Users should also closely follow the precautions and recommended heating times in their microwave oven’s instruction manual, and not exceed those times when heating water.
Beyond superheating, the FDA recommends using only microwave-safe cookware specially manufactured for microwave use. Glass, paper, ceramic, or plastic containers are generally suitable because microwaves pass through these materials, though some plastic containers can melt from the heat of the food. Metal pans or aluminum foil should not be used, as they reflect microwaves and can cause uneven cooking or damage the oven. The instructions that come with each microwave oven indicate the kinds of containers to use and how to check whether a container is microwave safe.
Regular cleaning of the microwave oven cavity and door with water and a mild detergent is also advised. Do not use scouring pads, steel wool, or other abrasives. If your microwave oven’s door, hinges, latches or seals are damaged, or the door does not open or close properly, the FDA says to contact the manufacturer. For more on microwave compatibility, visit our microwave safe mugs page.
Preventing Scalds from Hot Drinks
Hot coffee or tea in a ceramic mug can cause serious burns, especially for young children. The American Burn Association (ABA) notes that young children’s skin burns more quickly and deeply than adults’. To help prevent scald injuries, the ABA offers practical advice: keep hot drinks away from the table and counter edges, and use travel mugs with tight-fitting lids for all hot drinks.
While ceramic mugs typically do not have lids, you can still apply the edge-safety rule. Place your mug well back from the edge of a desk or table, particularly if children are nearby. If you are commuting or moving around with a hot drink, consider a travel mug with a secure lid. The ABA also recommends setting your water heater to no higher than 120°F (48°C) to reduce tap water scald risk, though that is separate from mug use. For more on travel mugs, see our travel mugs section.
Frequently asked questions
Can I check my ceramic mug for lead at home?
Yes. The FDA says consumers can buy lead-checking kits at hardware stores or online. These kits usually include swabs that you rub on the food-contact surface of the pottery. If leachable lead is present, the swab changes color. If a check shows lead, the FDA strongly advises against using the pottery for food or drinks.
Is it safe to microwave a ceramic mug?
Many ceramic mugs are labeled microwave safe, but you should always follow the mug’s care instructions. The FDA warns that heating water alone in a very clean mug can lead to superheating, which may cause the water to erupt violently. Adding instant coffee or sugar before heating reduces this risk. Also use only microwave-safe containers and follow your microwave oven’s manual.
How should I clean a stained ceramic mug?
General guidance from CorningWare for its stoneware suggests using non-abrasive cleansers and plastic or nylon cleaning pads. Avoid abrasive scouring pads and hard objects that can scratch the surface. If your mug is dishwasher safe, you can place it in the dishwasher, but check the manufacturer’s instructions first. For more tips, see our mug cleaning page.
For a deeper look at ceramic mugs, including different styles and features, visit our Ceramic Mugs category page.
