This week's checkWeekly materials QA — Tank 2, hydrophilic remover. Procedure limits: 10–30 % concentration by volume, target ≈20 %.
Step 1 of 5
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Appearance — sample vs. new material
Why this testThe remover is dyed pink so problems show. Fresh material is a clear, even pink. The penetrant that parts drag in is green and fluorescent — enough of it gives the whole tank a visible green cast, and a contaminated tank smears fluorescence back onto every part it processes. This is the cheapest test in the shop: hold the sample next to new material and just look.
Refractometer reading
How the instrument worksA refractometer measures how strongly the liquid bends light — and that depends on how much remover is dissolved in the water. In the eyepiece it shows up as a boundary between a blue field and a light one, crossing a scale: more remover pushes the boundary higher. Your only job is to read the scale exactly where the shadow edge sits.
Read where the shadow boundary crosses the scale in the eyepiece:
Convert on the calibration chart
Why the chartThe eyepiece reads °Brix — a raw optical number, not a concentration. The supplier's calibration chart converts it: find your Brix on the bottom axis, go up to the red line, then across to the left axis. The green band is the working window, 10–30 %.
Follow the guides on the chart — what concentration % does this Brix reading give?
Disposition — what does the log say this week?
Making the callTwo results are on the bench: the appearance against the reference, and the concentration against the 10–30 % limits. They don't always agree — and both have a say in what happens to the tank.
QA log
Your checks
Week
What was really going on
Appearance
Readings
Disposition
Process Control · Materials QA
Is the remover tank still in spec?
The hydrophilic remover (Method D emulsifier) is a working solution — water make-up dilutes it, evaporation concentrates it, and dragged-in penetrant contaminates it. So every week it gets a simple check: look at it, and measure it. Each step opens with a short note on why the test exists — read it first, then make the check.
Draw a sample and compare its appearance against fresh reference material.
Read the refractometer (°Brix), then convert to concentration % on the calibration chart.
Procedure limits: 10–30 %. Too weak → poor removal, heavy background. Too strong → risks stripping penetrant out of real defects.
There are four scenarios to work through — keep hitting “Next week” until you've seen all four.