Wait, what? o_o Are you sure you completely squeezed the blackhead out? And when you say that it reappears after five hours, is it the exact same blackhead at the exact same pore?

I've invested in a blackhead remover, it's basically this metal/stainless steel tool that has a small loop, which you use to press the pore. The advantage it has is that it applies even pressure as it forms a "circle" of pressure around that offending pore, which is hard to achieve if you're squeezing using your fingers.

Take a look, here's an example of a blackhead remover. http://www.amazon.com/Tweezerman-Whitehead...r/dp/B0006PLPBC

It's been an invaluable tool for me; great for squeezing pus-filled pimples out too. You might want to consider getting one yourself, if you haven't already got one.