When I opened my ancient tin of Kiwi black shoe polish, it was all dried up and broken into chunks. For a moment, I considered whether it might be possible to put the remaining polish in a microwave-safe container, melt it, and pour it back into the tin.
Then I came to my senses and realized that it couldn't possibly cost more than a few dollars to just buy some more. After all, I'd probably had my current supply for more than a decade.
In the meantime, I did the best I could with what was left in the old tin.