How to Fix a Microwave Oven After Putting Metal In It

Categorized as Microwave Repair and Troubleshooting
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Microwaving metal is never recommended. But accidents happen. If you’ve put metal in your microwave and seen sparks or damage, don’t panic. In many cases, some simple DIY repairs can get your microwave heating properly again.

Read on to learn the common metal-related microwave issues, step-by-step repair guides, safety tips, and answers to frequently asked questions. With a little effort, you can likely repair that microwave and avoid the cost of replacement.

Common Metal-Related Microwave Damage

Metals don’t absorb microwaves like food and water do. Instead, they reflect the radiation. This can cause:

  • Sparks and Arcing: Electricity arcs between metal pieces or from metal to the oven walls. This leaves black burn marks.
  • Waveguide Damage: The plastic or mica waveguide prevents radiation leaking near the magnetron. Arcing can melt holes here.
  • Component Damage: Severe arcing can destroy electrical components like switches, buttons, and control boards.

Thankfully, many metal-related issues can be fixed with simple repairs.

Fixing Arc Marks in the Metal Cavity

If you see black burn marks but no holes in the metal cavity, repair is straightforward. Here’s how to remove arc marks from the inner oven walls:

What You’ll Need

  • Sandpaper – 100-150 grit
  • Microwave cavity touch up paint
  • Clean cloths
  • Gloves for safety

Step-by-Step Guide

  1. Unplug the microwave and move it to a well-lit workspace.
  2. Locate all burn marks inside the cavity. Don’t try fixing exterior marks yourself.
  3. Lightly sand the rough areas to smooth and prep for painting. Don’t over-sand.
  4. Wipe away sanding debris with a clean cloth.
  5. Apply a thin coat of cavity touch up paint over the sanded areas.
  6. Let the first coat dry for a few minutes.
  7. Apply a second, thicker coat of paint to completely cover marks.
  8. Allow paint to fully cure for 24 hours before using again. Keep door open while drying.

With a little sanding and repainting, those annoying black marks will be gone! The touch up paint blends right in for an easy DIY fix.

Replacing a Damaged Waveguide

The waveguide is a crucial component that prevents radiation leakage near the magnetron. If arcing melted holes here, it must be replaced. Here’s how:

What You’ll Need

  • Clean cloth and cleaning spray
  • Replacement waveguide or mica sheet

Step-by-Step Guide

  1. Locate and remove the existing waveguide. It may slide out or require removing screws/rivets.
  2. Check if it’s actually damaged. Clean soot off with cloth and spray if intact.
  3. For full replacement, buy a new waveguide or cut a mica sheet to match the original size and shape.
  4. If using mica, cut holes to align with any screw or rivet holes.
  5. Install the new waveguide in the proper position. Replace any screws or rivets previously removed.
  6. Test that the microwave is heating properly before regular use.

Replacing a simple waveguide is much cheaper than an entire new oven. With the right precautions, your microwave can keep running safely.

When to Call an Appliance Repair Technician

While many metal-related issues can be DIY repaired, more serious electrical damage requires a professional. Call an appliance technician for:

  • External damage like door mesh or outer body damage
  • Holes and pitting on interior oven walls
  • Microwave powers on but won’t heat
  • Keypad and other electrical components not functioning
  • Strange noises, sparks, or other odd behavior

Never try to repair these issues yourself! Appliance components have extremely hazardous high voltages. Let a qualified pro tackle any electrical repairs.

FAQs About Microwaving Metal

Let’s wrap up with some frequently asked questions on metal use and microwave safety:

What types of metal should never go in a microwave?

It’s best to keep all metal out of the microwave when possible. The following types of metal items pose a high risk of arcing and damage:

  • Utensils like forks, spoons, knives, stirrers, pans, etc. The edges concentrate microwave radiation. Even non-sharp utensils can spark.
  • Aluminum foil and foil lids. Foil doesn’t absorb microwaves, instead reflecting them rapidly causing flash points and arcing.
  • Twist ties or wires used to close bags. The thin metal and sharp points are prime spots for sparks to occur.
  • CDs, DVDs, or other metal-containing discs. The reflective metal layer will arc when microwaved.
  • Thin metal jewelry like bracelets, watches, rings, etc. Flowing metal contours make jewelry risky.
  • Metallic paint or glitter on ceramics, plastics, etc. Hidden metal elements spark dangerously.
  • Electronics containing metal components and wiring. Laptops, tablets, etc will be destroyed and possibly start an electrical fire if microwaved.

Essentially, keep all non-food metals out! Glass, ceramic, and microwave-safe plastics are your best options. Never use metal cookware or aluminum foil in the microwave.

What happens if you microwave a spoon or fork?

Metal eating utensils seem harmless enough. But inserting a spoon, fork, knife, or other utensil into an energized microwave is a recipe for disaster! The handle insulates your hand while the tines concentrate the radiation into hotspots.

This rapid energy transfer causes arcing and leaves burn marks on utensils and oven walls. Sparks may even damage the internal microwave components. Though brief exposure of a couple seconds may only leave minor arcing marks, prolonged microwaving can destroy metal utensils and the oven itself. Always keep utensils out of the microwave!

Can you microwave styrofoam or paper with metal edges like take-out containers?

Metal-lined containers like inexpensive take-out boxes or cups with foil edges spark readily when microwaved. The foil strips concentrate energy at the rim, rapidly heating to ignition temperature. The resulting arc marks and potential fire danger make these containers unsafe for microwave use.

Always transfer leftover take-out food to a ceramic or glass microwavable dish before reheating. Don’t be tempted to microwave anything with metal components, even if most of the container is microwave-safe.

Is it safe to microwave a mug with metal decorative trim?

Microwave-safe mugs are designed with care. Quality mugs with metallic painted decoration, small non-conductive metal inserts, or thin metal rings around the rim are generally safe to microwave. However, inexpensive novelty mugs could have poorly implemented metal decorations that spark when heated.

Always closely monitor mugs when first testing them to ensure no arcing occurs. If any sparking is observed, discontinue use immediately. Also take care that any metal elements do not form a fully enclosed ring around the mug’s circumference, as this can lead to uneven heating and cracking.

What food containers are microwave-safe?

The safest food containers for microwave use include:

  • Glass, ceramic, or stoneware with no metal components, glazes, or paints. Inspect carefully for cracks that could lead to shattering.
  • High temperature plastics designed for microwave use will be labeled “Microwave Safe”. Avoid older plastic containers not specifically labeled. Melting could release hazardous chemicals.
  • Paper plates, towels, napkins, parchment paper, etc. Avoid recycled paper with hidden metal flecks that could spark.
  • Natural containers like potatoes, squash, corn husks, etc. are perfectly safe microwaved on their own.

Again, no metal pans, aluminum foil, or metallic paints! Microwave-safe means fully non-conductive.

How can you prevent arcing accidents?

To keep your microwave arcing and spark free:

  • Never microwave any metal objects. Check containers closely before use. Remove foil lids or metal ties.
  • Use microwave-safe cookware only. Glass, ceramic, and quality plastic are best.
  • Always place food centrally to avoid edge contact issues.
  • Use the oven rack if concerned about containers touching sides. Elevates above walls.
  • Start new containers on low power in 30 second increments to test.
  • Stop immediately if arcing, smoking, or sparks occur.

In Summary

Accidentally microwaving metal happens to most of us eventually. But with the right repairs, you can often fix the resulting damage rather than replacing the entire oven. For minor interior arcing, DIY touch up paint does the trick.

Severely damaged waveguides can be replaced with new ones. More serious electrical issues require appliance technician servicing for safety. With some effort, you can get your microwave heating properly again after a metal mishap.

By Rosie Elliott

I’m Rosie. I’m a professional chef with experience in Western, Mediterranean, and Italian cuisine. I’ve been cooking for over 15 years, and I have two daughters that keep me busy!

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