The deposition of carbon in the louver area of the inner divertor of JET was measured by means of a Quartz MicroBalance diagnostic (QMB) during 806 exposures in total for about 6479 seconds in various divertor conditions by means of a controllable shutter. The overall integrated frequency shift of the deposition crystal from the start of the measurements to the end was 23640Hz corresponding to an average carbon deposition flux of 5.5E-8g/cm2 sec or 2.8x1015 C/cm2 sec. Extrapolating this to the overall plasma divertor time of the MKII GB SR divertor (26.4 hours) yields a total amount of 35.4g of carbon layers deposited on the louver region. It was found that the deposition increases significantly with decreasing distance of the strike point position to the louver entrance. Elmy-H-mode discharges with the strike point on the horizontal target dominate the carbon layer formation on the QMB.