µNVR or myNVR is the name of our measuring device and analysis set for extractable soluble residues, which are often also called filmic or chemical residues. The underlying process is described in VDI/VDE 2083 Sheet 23. The residues are first extracted using a solvent, and then the solvent or a portion thereof is evaporated on a quartz balance, where the remaining residues are weighed.
Various extraction methods are provided for. Large surfaces are wiped off with a cloth, internal areas are rinsed out. Small parts can be completely immersed in a small beaker. Small surface areas are sampled by placing a drop onto them, small holes by filling with a drop of solvent. The extracted medium can be further diluted, if otherwise the extracted residue amount exceeds the range of the quartz balance. Thus, the method can cover several decades of residue levels.
A measurement usually only takes a few minutes and provides a residue mass (e.g. in µg) without complex calibration, which can also be related to the sampled area (then e.g. in mg/cm²). On the one hand, the method is significantly simpler and faster than the known, complex laboratory methods (e.g. IR spectroscopy, mass spectroscopy, SEM/EDX), but on the other hand it provides more information than the usual non-quantitative methods (test inks, contact angle measurement, etc.).