How to compare magnet strength in cat eye gel polishes?

Start with the right units and instrument. Measure magnetic flux density using a calibrated Hall-effect gaussmeter or a lab-grade teslameter, reporting results in Gauss (G) or Tesla (T). Note that 1 mT = 10 G and 1 T = 10,000 G. For cat eye systems, record the peak field at the magnet face and at standardized gaps (see next answers). Always zero the instrument and take multiple readings to calculate mean and standard deviation. Avoid smartphone magnetometers for absolute values; they are useful only for rough, relative checks.

Absolute Gauss numbers alone do not predict stripe quality; they are a starting point. Compare peak surface flux density measured at a fixed distance (commonly 1–3 mm) and then compare lateral gradients. Record peak Gauss at 2 mm as a reproducible reference because typical application separations (magnet to pigment layer) fall in this range. Also capture the field at 1 mm and 3 mm to characterize drop-off. Use magnet grade (N35–N52) as a secondary indicator—higher grade often yields higher surface flux—but geometry and pole arrangement usually determine the stripe sharpness.

Magnetic field strength decreases rapidly with distance; for a dipole-like magnet the far-field decay follows roughly an inverse-cube relation (field ~1/r^3), so small changes in gap produce large intensity differences. In practice, a 0.5–1 mm increase can noticeably soften the stripe. Therefore measure and report field at the realistic application distance: the combined thickness of gel, top coat, and any cap on the magnet. When testing, replicate the actual polish layer thickness and any magnet cap to ensure the measured field correlates with visual stripe intensity.

Use a calibrated Hall-effect gaussmeter with a small-area probe (0.5–2 mm sensor face) to capture local maxima and gradients. For spatial mapping, mount the probe on a motorized linear stage or a manual micrometer stage to scan across the magnet surface, logging field versus position. Lab teslameters and NIST-traceable calibration are preferred for procurement specs. Smartphone magnetometers and hobby gaussmeters can be used for quick comparative checks but are unsuitable for QC acceptance criteria due to calibration, sensor size, and orientation errors.

Define a written test protocol with these core elements: (1) reference magnet (master) with certified readings; (2) fixed measurement distances (for example 1 mm, 2 mm, 3 mm) using a nonmagnetic spacer jig; (3) probe orientation and position reporting (center, edge, and one lateral scan line); (4) test polish sample preparation with controlled layer thickness and pigment loading; (5) three repeats per point and acceptance windows (mean ± tolerance). Log peak flux and the lateral gradient (dB/dx) because gradient correlates with stripe sharpness. Use control charts to catch drift in magnets or polish batches.

Yes, weak or nonuniform magnets usually produce faint or broad stripes and can create inconsistent results across the nail plate. Two common failure modes are low peak flux (insufficient particle alignment) and low lateral gradient (poor stripe definition). Also watch for coatings, holders, or metal tooling that increase effective separation and reduce usable field. For manufacturing, ensure magnets are physically identical, oriented consistently, and tested against the reference magnet; replace or regrade magnets that show reduced peak or abnormal gradient profiles.