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If you've ever marvelled at the wonder of hand warmers – those hard flat packs that heat up when you bend them - then this video will amaze you.

A scientist from the University of Toronto, Canada, is filmed putting his hand in a jar of hot ice, or molten sodium acetate, so it crystallises around his fingers.

In a matter of seconds, the man's fingers are coated in a thick layer of ice. But instead of being cold, the scientist explains that his hand is actually quite warm, 'like a hot bath'.

Frozen: The scientist's hands are coated in a thick layer of hot ice, or molten sodium acetate. Because the ice is in fact warm, he is able to shake the crystals off

Eventually he's left with a block of ice stuck to his hand, but he's able to break free because the crystals are still soft, 'like ice cream'.

Explaining the process on YouTube channel NurdRage, the scientist, who does not give his name, said: 'This works because the substance is not "ice" as in water, but a different substance called sodium acetate trihydrate.  

'Normally solid sodium acetate was melted into a liquid that was then supercooled to below its melting point.

'In this state, adding nucleation sites, like the crystals on my hand, rapidly causes the rest of the sodium acetate to crystallise.'

The incredible video has been watched almost three million times.

'Hot ice' is created using sodium acetate, which is a salt created from the reaction between sodium bicarbonate, or baking soda, and acetic acid, or vinegar.

See what happens when you put your hand in hot ice

Hot ice is created using sodium acetate, which is a salt created from the reaction between sodium bicarbonate, or baking soda, and acetic acid, or vinegar. When a reaction with acid occurs, sodium acetate appears to freeze like 'ice' as the cold solution turns from liquid to solid (pictured)

During reactions, sodium acetate appears to freeze like 'ice' as the cold solution turns from liquid to solid.

This process is exothermic, meaning that the solid structure is warm to the touch.

Solutions of sodium acetate are used in certain types of hand-warmers.

When a metal button is pressed inside the plastic pouch containing the solution, it releases chemicals that starts the reaction. 

This causes the solution to crystallise, and this reaction generates heat.