Decision of the European Central Bank of 16 September 2010 on the authenticity and fitness checking and recirculation of euro banknotes (ECB/2010/14) (2010/597/EU)

1. Soil

Soil increases the optical density of euro banknotes. The following table specifies the maximum density increase of limit samples compared to new euro banknotes that euro banknotes may exhibit to be classified as fit:

Table 2

Optical density levels

Denomination	Maximum density increase of limit sample compared to new euro banknote	Filter
EUR 5	0,06	Magenta
EUR 10	0,06	Magenta
EUR 20	0,08	Magenta
EUR 50	0,07	Magenta
EUR 100	0,07	Magenta
EUR 200	0,04	Magenta
EUR 500	0,04	Magenta

Euro banknotes not meeting these criteria are unfit. NCBs keep reference euro banknotes showing a soil level derived from these criteria. The densitometric measurements of the reference euro banknotes are based on the following criteria:

• Standard for density measurements: ISO 5 parts 3 and 4

• Standard for the filters: DIN 16536

• Absolute measurements: standard calibration (white tile)

• Polarisation filter: on

• Aperture: 3 mm

• Illumination: D65/2

• Background: white tile standard calibration

The density increase of a reference banknote is the highest value between the averages of at least four measurement points measured on the front and on the back of the banknote in the unprinted area and without any watermark modulation.