Method for the offline determination of the content of inorganic solid particles in at least one aqueous resin solution, wherein the inorganic solid particles are selected from the group consisting of aluminum oxides (corundum), boron carbides, borates, silicon dioxides and silicon carbides, wherein said at least one resin solution is provided to form a wear layer on at least one support plate and is applied to said at least one support plate during a continuous coating process, wherein the resin solution is provided prior to application in at least one application container as part of a device for applying the solid particle-containing resin solution to the at least one support plate, wherein at least one sample of the solid particle-containing resin solution to be analysed is taken from the at least one application container in order to determine the content of inorganic solid particles in the resin solution, wherein the amount of inorganic solid particles in the resin solution is between 10 and 50% by weight, comprising the steps - Recording of at least one NIR spectrum from several reference samples with different solid contents using at least one NIR detector in a wavelength range between 500 nm and 2500 nm, preferably between 700 nm and 2000 nm, in particular preferably between 900 nm and 1700 nm; - Determining the solids content of said reference samples by ashing; - Assigning the determined solid contents to the recorded NIR spectra of said reference samples; - Creating a calibration model for the relationship between the spectral data of the NIR spectra and the assigned solid contents by means of multivariate data analysis; - Recording of at least one NIR spectrum from the at least one sample of the solid particle-containing resin solution using the same NIR detector in a wavelength range between 500 nm and 2500 nm, preferably between 700 nm and 2000 nm, in particular preferably between 900 nm and 1700 nm; and - Determining the solids content of the said at least one sample using the said at least one NIR spectrum of the said at least one sample and the calibration model produced. - Recording of at least one NIR spectrum from several reference samples with different solid contents using at least one NIR detector in a wavelength range between 500 nm and 2500 nm, preferably between 700 nm and 2000 nm, in particular preferably between 900 nm and 1700 nm; - Determining the solids content of said reference samples by ashing; - Assigning the determined solid contents to the recorded NIR spectra of said reference samples; - Creating a calibration model for the relationship between the spectral data of the NIR spectra and the assigned solid contents by means of multivariate data analysis; - Recording of at least one NIR spectrum from the at least one sample of the solid particle-containing resin solution using the same NIR detector in a wavelength range between 500 nm and 2500 nm, preferably between 700 nm and 2000 nm, in particular preferably between 900 nm and 1700 nm; and - Determining the solids content of the said at least one sample using the said at least one NIR spectrum of the said at least one sample and the calibration model produced.