100 percent cotton or wool fabrics should be safe to microwave when wet (the only real reason why anyone would microwave threads) since they’re organic threads. Don’t push it though. If they’re bone dry, microwaving them can cause a fire inside your microwave oven.
Polyester is a synthetic type of fabric. So can you microwave polyester thread? Should you microwave polyester? Or any other fabric, for that matter?
You may also like: Can You Microwave Flannel or Not? Learn the Truth
Can You Microwave Polyester Thread?
Don’t put the polyester thread in your microwave. Even when it comes to microwaveable fabrics, it’s still best that you don’t microwave them. Polyester can never be natural so it can never be safely microwaved like cotton.
It’s best to not try out if it’s microwaveable or not, but that applies to all fabrics, to be honest. Because polyester is basically plastic thread, it will melt when microwaved for a certain length of time that most cotton threads can survive.
Microwaving Wet Clothes to Dry Them Out
Speaking of which, cotton threads are safer to microwave (wet). Polyester threads for neck warmers or microwave bowl cozies shouldn’t be microwaved themselves.
The fibers of any thread are flammable though, so never microwave any of your threads dry. Some clothes use chemicals in creating their material—flammable or toxic chemicals that can cause you distress when exposed.
Polyester Melts in the Microwave like Any Other Synthetic Fiber
Polyester and nylon are synthesized instead of derived from plants and animals. They’re completely manmade. With that said, you’ve probably heard of people who’ve successfully microwaved polyester thread. However, they were probably very careful.
Or quite lucky. Or they’re lying. It is possible to microwave polyester and not end up with melted or burnt plastic that was once a shirt or a bag. Incremental heating to prevent reaching the melting point temperature can work but it’s a crapshoot.
One red flag is that results tend to vary depending on the person, his or her microwave, and other circumstances, including the quality of the polyester in question. The cheaper the polyester the likelier it’d melt faster at lower temperatures.
What is Polyester Thread Anyway?
Let’s talk more about polyester. A polyester thread is a synthetic fiber type commonly found in sportswear as well as various modern clothes. It’s known for its smoothness and silk-like softness. Since it achieved popularity in the Seventies (in the last century), it became pretty common.
The thread is particularly popular among those who sew for a living or as a hobby. It’s only second to rayon threads when it comes to viable embroidery material. Polyester is specifically a petroleum-based synthetic material. It’s amazingly versatile.
Polyester threads serve as substitutes for the more expensive cotton or wool. Both are more expensive than polyester threads due to the limits of production and their comparative scarcity. Therefore, it’s likely that many a good crafter’s kit has polyester threads instead of cotton threads.
The Benefits of Polyester Threads
Polyester thread has many benefits. They’re durable, they’re elastic, they’re impressively strong, and they’re resistant to abrasion, sunlight, or mold. Organic byproducts tend to suffer from rot and wear-down more than their synthetic counterparts like the polyester thread.
They have plastic in abundance inside of them. Not exactly the same plastic that turtles at sea are choking on, though. It’s important to remember that plastic is an umbrella term and not all plastics are made equal.
Some plastics are microwave-safe. Some are not and they easily melt under microwave pressure. Polyester is the latter type of plastic. Unless you want your item to melt or set aflame (thus ruining your microwave oven), keep it away from being microwaved.
Remember That Microwave Ovens Heat Things from the Inside Out
Microwave ovens—unlike conventional ovens that require preheating—heat things from the inside out. The microwaves or micro radio waves produced by the microwave oven’s magnetron specifically excite the water molecules of a given food item or even fabric, which raises the temperature quickly.
This also means that you might not get the moisture out the material from the start. The distribution of heat via microwave is uneven, leading to a big mess to clean up when the polyester ends up melting in some spots while remaining damp in other spots.
The Balancing Act of Microwaving Threads and Fabrics
If you go further than 7 minutes, you risk having the non-organic or synthetic parts of your clothing melt. You also need to keep from over-microwaving your clothing since super-dry organic material catches fire too.
If you’ve had success in microwaving felt in the past, you should keep your fingers crossed in any future attempts. It’s like surviving walking in open traffic. It’s not indicative of the safety of the action, it’s indicative of you being lucky.
Can Mercerized Cotton Thread be Microwaved?
If you’re new to sewing then you’ve probably never heard of the polyester thread alternative known as mercerized cotton thread. Before discussing how microwave-safe mercerized cotton is, let’s first discuss what mercerized cotton is first.
For those who aren’t in the know, mercerized cotton is a type of cotton that went through a special textile finishing treatment. It treats cotton with a solution of 20 to 30 percent sodium hydroxide, followed by being thoroughly washed.
This results in a shiny type of cotton that has improved dye uptake, reduced shrinkage, and increased resilience against getting torn apart. So can it be microwaved? Sure. It’s like cotton so it’s organic and is less likely to catch fire unless microwaved dry.
No, the sodium hydroxide won’t make it extra flammable but microwaving anything dry, including cotton items, will sooner or later result in it catching fire.
Additional Tips and Tricks
If you absolutely need to dry your clothes or fabrics in a hurry, use a blow dryer. If you insist on microwaving polyester, then face the consequences of a melted, burnt, or even flaming shirt full of toxic fumes that will keep your microwave unusable until all the smells and toxins disappear.
At best, microwaving a wet t-shirt will keep you warm but a little damp when you wear such threads. If you have to microwave natural fabrics, put them in a crank or bag then set the timer to 7 minutes to 10 minutes. Or microwave till 7 minutes in 1-minute increments.
This way, you can dry out some of your clothing or at least your socks.
- James V., “Can You Microwave Fabric?“, SewingIsCool.com, May 12, 2021
- James V., “Microwave-Safe Thread: Can You Microwave Polyester Thread?“, SewingIsCool.com, January 23, 2021
- “Is polyester sewing thread-safe for microwave use?“, Amazon.com, February 13, 2018