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A follow up question to this eggceedingly good one Why do rotten eggs float in water?

There are already some good methods here

https://www.wikihow.com/Tell-If-Eggs-Are-Raw-or-Hard-Boiled

It's clear enough why most of the methods work but...

In 'other tests' number 3, a torch is shone through the egg, but why does the boiled egg not allow as much light through as the liquid egg?

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The methods in the link you give are good.

In 'other tests' number 3, a torch is shone through the egg, but why does the boiled egg not allow as much light through as the liquid egg?

Have you never cracked a raw egg? The uncooked white is not white, it is a colorless jelly. When you shine a light through, it is only the yolk that will stop diffusion. If it is boiled, hard or soft, the white has coagulated and light does not go through.

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  • $\begingroup$ Thankyou, although is there also an explanation known for why the same substance, when cooked, becomes opaque, or does that get really complicated? $\endgroup$ May 26 at 12:35
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    $\begingroup$ @JohnHunter Complicated. news.ncsu.edu/2019/01/… When egg whites are raw, their proteins are curled up into tight balls. When heat is applied, those proteins uncoil and get tangled, forming a kind of mesh, which traps the surrounding water. This changes the color and the physical consistency of the egg white. $\endgroup$ May 26 at 12:51
  • $\begingroup$ @anna v thanks, good answer $\endgroup$ May 26 at 13:00
  • $\begingroup$ And in fact, this is why raw eggs are, or used to be, "candled." In a dim room, an inspector would place each egg in front of a light source. If significant embryonic development was seen, the egg would not be included in saleable items. $\endgroup$ May 26 at 15:00

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