As you may know, alginate doesn't stick to non-porous surfaces like skin and table tops. It DOES, however, stick to your shirt or to the carpet.
We've all done it. Get a little enthusiastic in your mixing or application and alginate ends up somewhere it shouldn't and you've got an alginate mess. If you're in the middle of an important job, you don't want to take time to clean up just then- and by the time you get around to it, the alginate is completely set.
Don't panic, it can be removed pretty simply. It is much easier to get out in the first few minutes because as it dries it hardens.
This same solution is great for cleaning up your mixing tools. Soak your Jiffy Mixer, kitchen whisk or mixing bowl and you should be able to just rinse off the alginate residue.
This also works for plaster based gypsum cements like LiquiStone.