S and Alive (5 kg) is a flowing "magic sand" as is well known.
It doesn't dry out, it always remains fluid.
What you should know and consider is:
The sand can be thermally treated and used for therapy.
Keep in mind that microwaves, for example, heat the sand from the inside, and therefore the sand inside could be hotter than it appears from the outside.
Do not seal the sand airtight. Sand needs to "breathe". The sand is generally dry.
Therefore, no bacteria or similar substances remain stuck to it.
The sand absorbs moisture from the surrounding air. Therefore, it is possible that during the months,
in which you heat, the sand appears "firmer", drier or "crumbly".
Just as their lips and mucous membranes are drier in the winter months, the same can be true for sand.
If that's the case, simply wet your hands and knead the sand once.
This may need to be done more often if the heating or room air is dry.
The sand is 99% "just" sand, without any chemical additives or preservatives.
You can't actually clean the sand.
However, if you feel you can somehow get the sand cleaner (during cold and flu season),
Then simply spread it out on a baking tray or similar and put it in the freezer over the weekend.
Nothing sticks to the sand – but whatever might have been there is gone after 48 hours at minus 30 °C.