--- title: "What Is Safe to Put in a Microwave: Dishes, Covers, Foil and Water" description: "Why glass and paper let the energy through and metal throws it back, the dishes and covers that belong inside, the tubs and bags that do not, superheated water…" url: "https://microwaverepair.center/guides/what-is-safe-to-put-in-a-microwave/" date_modified: "2026-09-26" --- Sparks, fire and the door # What Is Safe to Put in a Microwave: Dishes, Covers, Foil and Water What is safe to put in a microwave: heat-resistant glass, glass ceramic, microwave-safe plastic, pottery, porcelain and microwave-safe paper, covered with a paper towel, wax paper or microwave plastic wrap. Keep out metal pans, dishes with metallic trim, margarine tubs, takeout containers, brown paper bags and twist-ties. Water heated alone can boil over violently. By [MicrowaveRepair.center technical team](https://microwaverepair.center/authors/technical-team/) Published September 26, 2026 ## At a glance. Most of the sparks, melted lids and scalded hands that bring people to this site start with the container rather than the machine. The rules are short once you know why microwaves treat glass, plastic, paper and metal so differently. Read the whole guide ### Passes through Glass, paper, most plastics FDA explains that microwaves pass through these and are absorbed by the food. ### Bounces off Metal Reflected energy heats food unevenly and can damage the microwave. ### One-time tubs Not for reheating USDA says margarine tubs, takeout containers and whipped topping bowls stay out. ### Dish test 30 seconds on high Sharp's check: an empty dish that comes out very hot should not be used. In this guide 1. Why some materials heat and others let the energy pass 2. Dishes and covers that belong inside 3. What stays out, and what each one does 4. Water, coffee and tea heated on their own 5. Cold spots in the food itself 6. Step by step 7. Questions ## Why some materials heat and others let the energy pass FDA describes the three things microwaves do that make cooking possible: they are reflected by metal, they pass through glass, paper, plastic and similar materials, and they are absorbed by food. The water in the food turns that energy into heat. Deciding what is safe to put in a microwave comes down to that: a good container is one the energy passes through on its way to the food. Passing through does not mean staying cool. FDA points out that a glass or plastic dish can become hot from the food inside it, and that some plastics can be melted by that heat. That is why a container can be microwave-safe for a cup of soup and still warp under a dish of fatty meat or sugary sauce, which run far hotter. ### What a microwave-safe mark tells you A microwave-safe mark on plastic or pottery means the maker has tested it for that use. A container with no mark is not necessarily dangerous, but it has not been tested, and FDA's advice is to use cookware made for the microwave and to follow the container guidance in your own manual. Source: [FDA — Microwave Oven Radiation](https://www.fda.gov/radiation-emitting-products/resources-you-radiation-emitting-products/microwave-oven-radiation) — Microwaves are reflected by metal, pass through glass, paper and plastic and are absorbed by food; containers get hot from the food and some plastics melt; metal pans and foil should generally not be used; use microwave-safe cookware; superheated water can erupt and adding coffee or sugar first reduces the risk; some ovens should not be operated empty ## Dishes and covers that belong inside Sharp's drawer manual gives a clear list of utensils for cooking and reheating, and it matches what most makers print. It also reminds owners that a dish should not touch the cavity walls while it cooks, which matters in a compact drawer or a speed model with a small cavity. - Glass ceramic cookware. - Heat-resistant glass bakeware and bowls. - Plastics labeled microwave-safe. - Microwave-safe paper plates. - Microwave-safe pottery, stoneware and porcelain. - A browning dish, preheated only as long as its maker says. - As covers: paper towels, wax paper, microwave plastic wrap or a vented lid. ### Baskets and wood for a quick warm-up only Wood, straw and wicker appear on Sharp's list only for short reheating of foods with little fat or sugar, such as warming rolls. Left in longer, they dry out, char and can catch. Source: [Sharp — Microwave Drawer SMD2470AS, SMD2470AH, SMD3070AS Operation Manual](https://files.sharpusa.com/Downloads/ForHome/HomeAppliances/MicrowaveOvens/Manuals/TINSEB546MRR5_SMD2470AS_SMD3070AS%20OM_AW%2010-19-17.pdf) — Lists of utensils to use and not to use; wood, straw and wicker for short reheats only; foil in small flat pieces at least one inch from any surface; eggs in shell and sealed jars can explode; stir liquids, use wide-mouthed containers and let stand 20 seconds; dish test 30 seconds on high; USDA temperatures 145°F, 160°F and 165°F Close on a plain glass dish and a white ceramic bowl side by side on a microwave turntable. ## What stays out, and what each one does USDA's food safety service is blunt about one group: plastic storage containers such as margarine tubs, takeout containers, whipped topping bowls and other one-time-use containers should not be used in microwave ovens. Sharp's list adds the rest. - Metal pans and bakeware, which reflect the energy and can arc at their edges. - Dishes with gold or silver trim, where the thin metal band sparks and blackens. - Glass that is not heat-resistant, which can crack as the food heats. - Margarine tubs and other plastics not made for the microwave, which can warp or melt. - Recycled paper products and brown paper bags, which can scorch or catch. - Food storage bags, which are not made for cooking heat. - Metal twist-ties, which arc and can set the bag alight. ### Foil: a narrow exception, and makers disagree FDA's general advice is that metal pans and aluminum foil should not be used, and NFPA says never. Some manufacturers do allow a small, carefully placed piece: Sharp permits small flat pieces smoothed onto the food to shield thin areas, kept at least one inch from every surface of the cavity. If your manual does not mention foil, leave it out. Crumpled foil, foil touching a wall and foil-lined takeout boxes are the classic cause of sparks. ### Eggs in the shell and closed jars Sharp's safety instructions warn that whole eggs in their shells and sealed containers such as closed glass jars can explode. Steam builds inside with nowhere to go. Pierce potatoes and sausages, slit cooking bags, and take lids off jars before heating what is inside. Source: [USDA FSIS — Cooking Safely in the Microwave Oven](https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/cooking-safely-microwave-oven) — Margarine tubs, takeout containers, whipped topping bowls and other one-time-use containers should not be used; microwaves can leave cold spots, so stir or rotate midway and allow standing time before checking with a food thermometer; [Sharp — Microwave Drawer SMD2470AS, SMD2470AH, SMD3070AS Operation Manual](https://files.sharpusa.com/Downloads/ForHome/HomeAppliances/MicrowaveOvens/Manuals/TINSEB546MRR5_SMD2470AS_SMD3070AS%20OM_AW%2010-19-17.pdf) — Lists of utensils to use and not to use; wood, straw and wicker for short reheats only; foil in small flat pieces at least one inch from any surface; eggs in shell and sealed jars can explode; stir liquids, use wide-mouthed containers and let stand 20 seconds; dish test 30 seconds on high; USDA temperatures 145°F, 160°F and 165°F ## Water, coffee and tea heated on their own Plain water in a clean cup can heat past its boiling point without bubbling. FDA calls this superheating and has received reports of serious scalds when the cup was moved or a spoonful of instant coffee was dropped in and the water erupted. Adding the coffee or sugar before heating greatly reduces the risk, and FDA's advice is not to heat liquids longer than the manual recommends. Sharp adds practical steps: stir the liquid before and halfway through heating, use a wide-mouthed container rather than a narrow-necked one, and let it stand in the microwave for at least 20 seconds before lifting it out. NFPA's tip sheet notes that scald burns are the leading cause of injury from microwave ovens. Source: [FDA — Microwave Oven Radiation](https://www.fda.gov/radiation-emitting-products/resources-you-radiation-emitting-products/microwave-oven-radiation) — Microwaves are reflected by metal, pass through glass, paper and plastic and are absorbed by food; containers get hot from the food and some plastics melt; metal pans and foil should generally not be used; use microwave-safe cookware; superheated water can erupt and adding coffee or sugar first reduces the risk; some ovens should not be operated empty; [Sharp — Microwave Drawer SMD2470AS, SMD2470AH, SMD3070AS Operation Manual](https://files.sharpusa.com/Downloads/ForHome/HomeAppliances/MicrowaveOvens/Manuals/TINSEB546MRR5_SMD2470AS_SMD3070AS%20OM_AW%2010-19-17.pdf) — Lists of utensils to use and not to use; wood, straw and wicker for short reheats only; foil in small flat pieces at least one inch from any surface; eggs in shell and sealed jars can explode; stir liquids, use wide-mouthed containers and let stand 20 seconds; dish test 30 seconds on high; USDA temperatures 145°F, 160°F and 165°F; [NFPA — Microwave Oven Safety tip sheet](https://content.nfpa.org/-/media/Project/Storefront/Catalog/Files/Safety-tip-sheets/MicrowaveSafetyTips.pdf) — Never use foil or metal; scald burns are the leading cause of microwave injury; stir and test food before giving it to children; never heat a baby bottle in the microwave ## Cold spots in the food itself A container can be perfect and the food still unsafe. USDA warns that microwaves can cook unevenly and leave cold spots where harmful bacteria survive, and advises stirring or rotating food midway through and allowing standing time, which completes the cooking, before checking the temperature with a food thermometer. Sharp's manual prints the USDA temperatures to check against: 145°F for fish, 160°F for pork, ground beef, veal, lamb and egg dishes, and 165°F for leftovers, deli and carry-out food and all poultry. Use a thermometer approved for the microwave if it stays in during cooking; otherwise take the reading after the food comes out. ### Food for children and baby bottles NFPA advises stirring and testing food before giving it to a child, and never heating a baby bottle in the microwave: uneven heating leaves hot pockets in milk that feels lukewarm on the outside. Warm a bottle in a bowl of warm water or under the tap instead. Source: [USDA FSIS — Cooking Safely in the Microwave Oven](https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/cooking-safely-microwave-oven) — Margarine tubs, takeout containers, whipped topping bowls and other one-time-use containers should not be used; microwaves can leave cold spots, so stir or rotate midway and allow standing time before checking with a food thermometer; [Sharp — Microwave Drawer SMD2470AS, SMD2470AH, SMD3070AS Operation Manual](https://files.sharpusa.com/Downloads/ForHome/HomeAppliances/MicrowaveOvens/Manuals/TINSEB546MRR5_SMD2470AS_SMD3070AS%20OM_AW%2010-19-17.pdf) — Lists of utensils to use and not to use; wood, straw and wicker for short reheats only; foil in small flat pieces at least one inch from any surface; eggs in shell and sealed jars can explode; stir liquids, use wide-mouthed containers and let stand 20 seconds; dish test 30 seconds on high; USDA temperatures 145°F, 160°F and 165°F ## Where to stop If a dish sparks, stop the microwave at once and remove it once the cavity has cooled. Stop using the microwave and book a visit if sparks continue with nothing metal inside, if the waveguide cover or cavity paint is burned, or if melted plastic has run into the vents or the turntable drive. Do not open the outer cabinet to clean out melted material. Written by [MicrowaveRepair.center technical team](https://microwaverepair.center/authors/technical-team/). Technicians who repair home microwaves, writing from what each service call showed and from the makers' own manuals. Sources: [FDA — Microwave Oven Radiation](https://www.fda.gov/radiation-emitting-products/resources-you-radiation-emitting-products/microwave-oven-radiation) · [USDA FSIS — Cooking Safely in the Microwave Oven](https://www.fsis.usda.gov/food-safety/safe-food-handling-and-preparation/food-safety-basics/cooking-safely-microwave-oven) · [Sharp — Microwave Drawer SMD2470AS, SMD2470AH, SMD3070AS Operation Manual](https://files.sharpusa.com/Downloads/ForHome/HomeAppliances/MicrowaveOvens/Manuals/TINSEB546MRR5_SMD2470AS_SMD3070AS%20OM_AW%2010-19-17.pdf) · [NFPA — Microwave Oven Safety tip sheet](https://content.nfpa.org/-/media/Project/Storefront/Catalog/Files/Safety-tip-sheets/MicrowaveSafetyTips.pdf) ## Step by step. Four steps, in the order worth doing them. 01 ### Look for the mark Check the bottom of the dish or container for a microwave-safe mark and for any metal trim. 02 ### Test an unmarked dish Sharp's method: put the empty dish in and run it on high for 30 seconds. 03 ### Feel it with care A dish that is very hot afterward is absorbing energy and should not be used for cooking. 04 ### Cover and vent Cover with a paper towel, wax paper or microwave plastic wrap, leaving a gap for steam. For the heart of your home. ## Questions owners ask. ### Can I microwave food in its takeout container? Not a plastic one meant for a single use: USDA lists takeout containers among those to keep out. Move the food to a glass or microwave-safe dish, and never microwave a box with a metal handle or foil lining. ### Is plastic wrap safe in a microwave? Wrap sold for microwave use is, as a cover. Leave a corner open so steam can escape and keep it from resting on fatty or sugary food, which gets hot enough to soften it. ### Why did my coffee mug spark? Most likely a metallic glaze or a painted rim. Metal trim, even a thin line of gold, reflects the energy and arcs. Stop the cycle and move to a plain mug. ### Can I run the microwave empty to test it? No. FDA notes that some models should not be operated empty, because the energy has nothing to absorb it. Put a cup of water in if you need to check that it heats. ## The problems behind it. Each has a page of its own: what it usually means and the causes in the order worth checking. [All 17 problems](https://microwaverepair.center/problems/) Stop using it ### Sparks Flashing Inside a Microwave 6 causes, cheapest first Problem ### Microwave Runs but Food Stays Cold 7 causes, cheapest first Stop using it ### Burning Smell From a Microwave 6 causes, cheapest first ## When it needs a technician. The repairs on the right are where this guide ends when the checks do not settle it. ### Microwave magnetron repair Replacing the tube that makes a microwave's heat, after proving the parts that feed it are sound, and renewing the waveguide cover and any pitted metal where sparks have been. ### Microwave turntable and motor repair Getting the glass plate turning again, from a cracked coupler or a roller ring clogged with spill to the small motor beneath the cavity floor. ### Microwave diagnostic visit A visit that times a cup of water against the clock, checks the door and its switches, then tests the high-voltage section, the controls and the moving parts one at a time until a single part is named. ## More in sparks, fire and the door. What to do when a microwave sparks, when smoke or a flame shows behind the window, when the door is bent or will not seal, and what is safe to put inside in the first place. [The whole section](https://microwaverepair.center/guides/safety-and-food/) Keeping people and the kitchen safe ### A Fire Inside the Microwave: Door Shut, Power Off, Then Watch What flames and smoke behind the glass look like, cutting power at the plug or the breaker, when to leave and call, what sets the cavity alight and what to check once it is out. Keeping people and the kitchen safe ### A Microwave Door That Will Not Seal: Unplug It and Leave It Off How the door, its window screen and its interlock switches keep the energy in, the signs of a door that no longer closes square on each kind of microwave, and why the fix is never a home job. Guides ### All 18 guides Six sections, by what you are trying to find out. --- **[Read on the site: What Is Safe to Put in a Microwave: Dishes, Covers, Foil and Water](https://microwaverepair.center/guides/what-is-safe-to-put-in-a-microwave/)** **[Book a visit with MicrowaveRepair.center](https://microwaverepair.center/schedule/)**