Question: why don't marshmallows set alight when you roast them on a fire?

Matthew Tomlinson answered on 22 Nov 2013:

I think I’m right in saying marshmallows will burn, if they get hot enough. The reason they don’t most of the time is because when they are being roasted the temperature does not get hot enough to ignite the sugars. What happens is caramelisation, the sugars start to melt and combine together, which is why you get the crispy outer layer. However, if you were to leave the same part of the marshmallow over the fire for long enough, the sugars will start to burn and ignite.

I hope that answers your question!