Why this testAfter drying, the part goes into a cloud of this fine white powder. It clings to the surface and works like blotting paper — wicking penetrant back out of any crack and spreading it wide enough to see. That only works if the powder is bone-dry and fluffy, so it dusts into a light, even coat. Moisture — humid air, a lid left open, a damp part — cakes it into lumps that can't coat evenly, and a spot the powder misses develops nothing.
Turn the sample over next to the reference — how does the powder behave?
UV speck test — dragged-in penetrant
Why this testEvery glowing speck is a grain of powder soaked in penetrant — carried in by parts that went into the chamber before they were fully dry. In service, one of those grains can land on a clean part and glow like a real crack: a false indication that wastes inspection time or scraps a good part. So the procedure caps them: no more than 10 specks inside the 100 mm circle.
Count the fluorescent specks inside the marked circle (specks outside it don't count):
Aqueous developer — hydrometer
Why this testThe dip tank is developer powder dissolved in water, and everything depends on concentration — too dilute and the dried film is too thin to pull penetrant out of tight cracks. You can't see concentration, but you can weigh it: more dissolved solids make the liquid denser, and the hydrometer floats higher in a denser liquid. So the number on the stem at the surface line — the specific gravity — stands in for concentration.
Read the stem scale at the liquid surface line:
Disposition — what goes in the QA log?
Making the callReadings don't protect parts — dispositions do. Put this week's three results — powder condition, speck count, specific gravity — against their limits and decide what the log says.
QA log
Your checks
Week
What was really going on
Powder
Readings
Disposition
Process Control · Materials QA
Will the developer still do its job?
The developer is the last material a part sees — it draws penetrant back out of defects and makes the indication visible. Two forms, two simple checks. Each step opens with a short note on why the test exists — read it first, then make the check.
Dry powder: it must be fluffy and free-flowing (moisture cakes it), and clean under UV-A — every glowing speck is dragged-in penetrant, and the limit is 10 specks inside the marked circle.
Aqueous developer: concentration is checked with a hydrometer — read the specific gravity at the surface line; limits 1.040–1.080, target ≈1.060.
There are four scenarios to work through — keep hitting “Next week” until you've seen all four.