I know ZIP about salt bath annealing but,
Let's think this thru.....
At one atmosphere and not contained, ie
"out in an open pot, not in a pressure vessel" water will boil off at 212F...... GONE..... like it can't hide out in a pocket somewheres and jump out or "explode" later. The water will be GONE from the salt by the time it gets up around 212 degrees....it cannot exist above 212F, except under pressure.
I have heated some lead in my day. Lead will also "explode" if you drip/drop sizable hunks of water into it at heat. The mechanism is simple, a gobbet of water gets under the surface of the HOT lead, turns to steam and HAS TO escape, so it blurps out the top of the lead pot splattering lead. But out here on the left coast, in the rain, in the real world where guys are doing hundreds/thousands of pounds (Schnitzer, Metro Metals, Brad's Baits) the guys don't worry about heat up..... it's just called "drying out the equipment". It's only after you're up to heat that you need avoid dropping liquid H2O into the batter.
That said, me being a Safety Geek (read "scared of everything") I might opt to run 'er up to heat out in the yard "just in case she burps" and watch out the front room winder until she's molten.
Let 'er cool, bring to your work station and have at 'er.