Hot and Cold Glass.

Sitting in the shed the other day and the sun was glaring through the big glass window right onto my bench, great as you can’t beat natural light when working on fine things. One thing struck me as being odd, the outside of the glass was very hot but it was cool on the inside, how come it’s not hot all the way through? it’s only a fairly thin single pane of glass. There’s probably a very simple explanation but I don’t know what it is, hence the question.

Re: Hot and Cold Glass.

Great question, Jem! I like how your mind works!
I'm guessing here, but assuming the shed is warmer inside than the ambient outside temperature, heat will be conducted through the glass from inside to outside, so perhaps that along with the direct sunlight falling on the outside is part of the reason?

Re: Hot and Cold Glass.

Could it be that the sun was focusing on the outside surface of the glass, after reflecting off the inside surface, similar to the way a magnifying works.
If a laser is directed on the edge of a piece of glass, in can be seen at the opposite edge, but not on the face of the glass. Which demonstrates that light bounces around between the surfaces, even on a thin piece of glass. [I don't think that's relevant, but it's interesting all the same]

Re: Hot and Cold Glass.

Something to do with glass being a relatively poor conductor of heat? Think of a thin glass of boiling water it is still possible to comfortably hold the glass only a short distance from the liquid.

Re: Hot and Cold Glass.

Wow this is all scientific, but yes i agree with you all...

Re: Hot and Cold Glass.

I think it is because the outside of the glass also reflects the heat back out.

Re: Hot and Cold Glass.

Thank you all for that information folks.
I vaguely remember a TV program many years ago, I think it was called "How" and the question was asked "How can you get fire from water?" The answer was you take a sheet of fairly thick flat ice, say from the top of a pond or river, and hold it to the Sun as a magnifying glass to light a piece of paper, they demonstrated it and it worked, so reflection must have a lot to do with it.

Re: Hot and Cold Glass.

I have worked in many power stations and have lost count of the number of times there have been fires caused by people leaving a scaffolding plank leaning against an uninsulated steam pipe. Steam is just water isn't it?