If I may assert that sourdough is particularly associated with Alaska, then transporting sourdough may be said to be a particularly Alaskan problem.
The problem with moving sourdough is that motion and warmth activate the yeast, causing expansion. Atmospheric changes also affect it, which makes Alaska’s most common mode of travel—flight—particularly problematic. A sourdough pot, sealed enough to prevent spillage, becomes a pressure bomb under these circumstances.
I have never personally experienced a sourdough accident in my luggage. I have, however cleaned up enough spilled and dried sourdough to fear the possibility.
We have two methods of transporting sourdough starter that prevent unpleasantness, even through high altitude airline flights.
The most convenient method is to spread a thin layer of healthy starter on a cookies sheet lined with waxed paper or baking parchment, and leave it to dry. The resulting crust may be collected in aplastic bag and carried in luggage or a pocket to its destination. There it can be reconstituted by soaking in warm (not hot) water. Add flour and water in equal measures to this, until a few cups of starter begin to bubble.
While this is the most convenient way to carry sourdough, it’s a little less likely to reconstitute successfully. Drying in an open room provides a lot of chances for mold spores to attack it, which can ruin the sourdough. It seems likely that the beneficial yeasts may dies or weaken too much in tthe process to reconstitute readily.
The second method is slightly less convenient to carry, but takes less time to assemble, and almost never fails to reconstitute.
Add flour to a small dollop of healthy sourdough starter until it thickens to a doughy ball. Put a small amount of dry flour in a ziplock back, and place your dough ball on top of it. Press most or all of the air out of the bag and seal. This will allow space for expansion, should it occur, without bursting the bag. For extra security, place this bag inside another ziplock bag, and seal.
Since 9/11, I mark the bag “Sourdough Starter: water and wheat flour—Do Not Open!” One hopes all TSA agents can differentiate flour from the other suspicous white powders they watch for, but just in case . . . .
When you reach your destination, reconstitute your sourdough starter as above.
Either of these methods would likely make the sourdough safe to mail, as well.
I have a lot to say about sourdough as we approach our starter’s 21st anniversary.