Anything flammable will burn if it gets hot enough. How hot depends on the particular substance and other factors such as the air pressure and how much oxygen is around. 100% cotton can auto-ignite if it gets hot enough.

There's too many factors (density, how it was woven, if there's any oil/grease on it) to say definitively what that temperature is, but in general I wouldn't put cotton in the microwave or in the oven.

Similarly, if you get any kind of oily stain on clothing, you shouldn't put it in the dryer! That's one of the ways you can get a dryer fire. The auto-ignition temperature of the cloth is lowered by the oil (yes, even vegetable oil).

The same goes for bowl buddies. I always use 100% cotton thread in upper and bobbins. If you embroider use rayon never polyester.

I think the potato bags are made to keep the potato warm until you are ready to eat it. You can put the potato in it after it is done.

Microwave bowls were intended to be put under the dish as it is being heated and used as a handle to take the hot dish out, but I don't do that. I use another pot holder to handle the dish to put it into the cloth bowl to transport to wherever. And they are wonderful for a dish of cold ice cream, too , as illinois said.

A thought I had was, maybe the fabric wasn't washed before it was sewn. The sizing and other toddies in the fabric very well may be the issue

My thoughts exactly!

I buy nothing at craft shows or use nothing in my microwave made of fabric as I never know what people has used and yes polyester thread will start a fire I do make rice bags and buy everything at my Bernina shop telling them exactly what I want it for and they help me pick out everything thread included and yes be very careful how long you leave it in

That's how I do it. And, yes, cotton will burn if it gets hot enough. I don't use potato bags.

I found by just washing the potatoe(s), and wrapping them in a paper towel to keep them moist does the trick for me. Have always been afraid to try one of those potato bags for that very reason................FIRE!

I think we all know cotton will burn. But it was touted all over the place that cotton is safe for this particular use. I use paper bags for my potatoes in the micro wave and I think paper might also be combustible..

Although this is a serious subject and I agree that it is better not to use potato bags or bowl cozies in the microwave, I can't help but be reminded of an article I read a number of years ago. It was about how many microwave fires were started by people drying their underwear in the microwave. It advised everyone that putting anything made of fabric in the microwave was a potential fire-starter. Funny, it would have never occurred to me to dry my underwear in a microwave. Talk about commonsense...