Your Free A4 Sample Arrived. Here Is the 5-Minute Test.

We send free A4 samples worldwide — you only cover the courier. But a sample only earns its keep if you put it through something. Here is the test we would run in your shoes. Total time: about five minutes.

1. Write, wait, wipe

Draw a few solid strokes with any dry-erase marker and leave them for five minutes — run the other checks in the meantime. Then wipe with a dry cloth or a felt eraser.

Good film: the ink lifts in one or two passes and leaves no shadow. If you have to scrub, or a grey ghost stays after a firm wipe, that is a coating problem — not your marker.

2. Tilt it into the light

Hold the panel at an angle to a window or a lamp and look across the surface, not into it. You are checking that the film is even: no pinholes, no orange-peel texture, no scratches from handling.

A white panel will look glossy — by design, 88–95 GU. Green and black will look flat — also by design, 10–16 GU, so a projector or a bright window does not bounce straight into your audience's eyes.

3. Trust the edge

The A4 sheet has cut edges, and bare steel at the cut is normal — every cut-to-size panel has it. What protects the panel is the zinc layer under the paint, 20–80 g/m² on our line, plus 22–24 µm of total dry coating film on the face. In a finished board, the frame covers the edges anyway.

Bonus 30 seconds: bend a corner over 90° and back. The coating should crease with the steel — if flakes fall off, that is a red flag.

What we test before it ships

Every batch leaves our Bazhou plant after film-thickness measurement, glossmeter readings and write-and-wipe checks on the same coating line your sample came from. Your desk test should land in the same place our bench does.

If anything in those five minutes looks wrong, write to us with a photo — that is exactly what samples are for.

*— Yueyang Technology, Bazhou, Hebei. Write to us — David Hu, General Manager.*