Why glossy surface condense first?

Fred Harwood_2

Shiny surfaces foster earlier detection of condensation by the human eye. Other surfaces tend to blend or obscure rather than reveal the first appearance of moisture on cool surfaces.

A murder mystery detective will use a compact mirror held to a victim's nose and mouth to detect the slightest breath, never a handy stone or less reflective object, even should the stone or object be colder than the mirror.

This information comes from an aging resource known locally as The World According to Fred.

Hollis

Why do glossy/shiny surfaces condense first?

I remember in school to measure dew points you added a bit of ice to a shiny metal container of water. When moisture started to condense on the container you noted the temp on the thermometer in the water to determine dew points.

So a question to you that have studied heat. Why do bathroom mirrors and even glossy paint (say in rooms with showers) condense first? Have to do with radiant energy bouncing off that surface making it relatively cooler?

Brad White_191

Surface tension

The rougher surfaces still condense. See latex paint in the bathroom after a shower, you can still draw your finger through it. The moisture is there but is less visible because there is less reflection behind it and is also hiding in the nooks and crannies of the paint. This in turn breaks up the surface tension of the moisture (the natural cohesion between like particles). Drawing your finger across the surface "reconnects" the droplets from what is otherwise less-visible.

On smooth surfaces (glass, mirrors, polished steel -all below the dewpoint of course), the moisture deposits itself in one nearly continuous sheet because the flat plane allows the surface tension of the moisture to thrive.

The greater reflection enhances the view.

The actual surface temperature is not significantly different, just the emissivity. Such surfaces at equal temperatures may feel cooler due to greater conductivity.

Hollis

Thank you guys!