Reading about Hawking's Radiation I understood that black holes lose energy over time - which is logical in some way (otherwise they would be there forever and heat death would never technically happen)
But - how exactly does it "evaporate"? What happens when it no longer contains enough mass within it's Schwartzshild radius ? Does it explode somehow? Transforms into "regular matter"? Simply vanishes over time? Or?
A black hole evaporates by radiating away energy in the form of photons, gravitons, neutrinos, and other elementary particles in a process that involves quantum field theory in curved spacetime. This causes it to lose mass, and so its radius shrinks. It remains a black hole as it shrinks. The increased spacetime curvature at the horizon makes it radiate more and more powerfully; its temperature gets hotter and hotter. The more mass it loses, the faster it loses what it has left!
I agree with Michael Walsby that small black holes are speculative and have not been detected. I am not so sure that they never will be, and it is important to understand how they behave.
As the Wikipedia article explains, for a non-rotating black hole of mass $M$, the radius of the event horizon is
$$R=\frac{2G M}{c^2}$$
and the Hawking temperature is
$$T=\frac{\hbar c^3}{8\pi k_B G M}.$$
If you make the approximation that the black hole is a perfect blackbody, then the radiated power is
$$P=\frac{\hbar c^6}{15360\pi G^2 M^2}$$
and the lifetime of the hole is
$$t=\frac{5120\pi G^2 M^3}{\hbar c^4}.$$
Notice the simple power dependence of all these quantities on $M$. Everything else is just constants. It is easy to substitute numerical values and compute the following table for black holes whose masses range from that of an asteroid down to that of a bowling ball:
$$\begin{array}{ccccc} M\text{ (kg)} & R\text{ (m)} & T\text{ (K)} & P\text{ (W)} & t \text{ (s)}\\ 10^{20} & 1.49\times10^{-7} & 1.23\times10^{3} & 3.56\times10^{-8} & 8.41\times10^{43}\\ 10^{19} & 1.49\times10^{-8} & 1.23\times10^{4} & 3.56\times10^{-6} & 8.41\times10^{40}\\ 10^{18} & 1.49\times10^{-9} & 1.23\times10^{5} & 3.56\times10^{-4} & 8.41\times10^{37}\\ 10^{17} & 1.49\times10^{-10} & 1.23\times10^{6} & 3.56\times10^{-2} & 8.41\times10^{34}\\ 10^{16} & 1.49\times10^{-11} & 1.23\times10^{7} & 3.56\times10^{0} & 8.41\times10^{31}\\ 10^{15} & 1.49\times10^{-12} & 1.23\times10^{8} & 3.56\times10^{2} & 8.41\times10^{28}\\ 10^{14} & 1.49\times10^{-13} & 1.23\times10^{9} & 3.56\times10^{4} & 8.41\times10^{25}\\ 10^{13} & 1.49\times10^{-14} & 1.23\times10^{10} & 3.56\times10^{6} & 8.41\times10^{22}\\ 10^{12} & 1.49\times10^{-15} & 1.23\times10^{11} & 3.56\times10^{8} & 8.41\times10^{19}\\ 10^{11} & 1.49\times10^{-16} & 1.23\times10^{12} & 3.56\times10^{10} & 8.41\times10^{16}\\ 10^{10} & 1.49\times10^{-17} & 1.23\times10^{13} & 3.56\times10^{12} & 8.41\times10^{13}\\ 10^{9} & 1.49\times10^{-18} & 1.23\times10^{14} & 3.56\times10^{14} & 8.41\times10^{10}\\ 10^{8} & 1.49\times10^{-19} & 1.23\times10^{15} & 3.56\times10^{16} & 8.41\times10^{7}\\ 10^{7} & 1.49\times10^{-20} & 1.23\times10^{16} & 3.56\times10^{18} & 8.41\times10^{4}\\ 10^{6} & 1.49\times10^{-21} & 1.23\times10^{17} & 3.56\times10^{20} & 8.41\times10^{1}\\ 10^{5} & 1.49\times10^{-22} & 1.23\times10^{18} & 3.56\times10^{22} & 8.41\times10^{-2}\\ 10^{4} & 1.49\times10^{-23} & 1.23\times10^{19} & 3.56\times10^{24} & 8.41\times10^{-5}\\ 10^{3} & 1.49\times10^{-24} & 1.23\times10^{20} & 3.56\times10^{26} & 8.41\times10^{-8}\\ 10^{2} & 1.49\times10^{-25} & 1.23\times10^{21} & 3.56\times10^{28} & 8.41\times10^{-11}\\ 10^{1} & 1.49\times10^{-26} & 1.23\times10^{22} & 3.56\times10^{30} & 8.41\times10^{-14}\\ 10^{0} & 1.49\times10^{-27} & 1.23\times10^{23} & 3.56\times10^{32} & 8.41\times10^{-17}\\ \end{array}$$
As you can see, as the hole shrinks, it gets tremendously hot and radiates enormous amounts of power. This is why Hawking titled one of his papers "Black hole explosions?"
As far as I know, no one is sure whether a hole evaporates completely or leaves behind a Planck-scale remnant.
No black hole has ever yet evaporated;the energy they absorb from their surroundings far exceeds what they lose by Hawking radiation. It may well be the case that the universe will collapse & be recycled in a Big Crunch before the first black hole has had time to evaporate. To those who say the universe is expanding too fast to collapse,I say there is not unanimous agreement among cosmologists for that. At present,a Big Crunch can't be ruled out.
What will happen if you shine a light on a presumably dead black hole will the light still curve or will it travel with no interference. Even though an black hole disappears from space and existence entirely is there still a way to prove that’s it’s there or nothing is left. I understand it’s loss of mass and sheer gravitational force causes it to explode by evaporation from the outside from its radiation. But maybe they get so small that there is no way to see it from the naked eye but from something microscopic because of its infinite density.
