The degree of damage depends on the wavelength of the radiation

Now, one could claim that is does not matter in terms of the degree of damage whether materials are irradiated with electromagnetic radiation (i.e. light with 546 nm or UV radiation with 389 nm).

However, this is not the case!

In a paper by Judd and Hilvert, an analysis at 546 nm determined a relative damage factor of 1 based on the extent of the damage (i.e. the measured colour changes, brittleness etc.); however, at i.e. 389 nm, a relative damage factor of 90 – and at 365 nm, even 135! (see image)

That means that ideally, an object irradiated with i.e. 389 nm ages 90 times faster than one irradiated with 546 nm!

Not all materials react equally

According to their particular molecular structure, different materials react differently.

Here, you will find an exemplary compilation of materials with properties which can be critical in photochemical terms / Limit wavelength of the spectral transmission edge (1%), considering the colour reproduction at a rate of Ra 98%

• 385 nm plastics with inherent UV protection (for interior application)
• 385 nm destruction of modern binding agents (interior application)
• 385 nm wood components, untreated
• 385 nm organic stains in modern paint media (interior application)
• 385nm paper (basis: rags)
• 395 nm historic binding agents
• 395 nm historic textiles with pre-existing damage
• 400 nm organic stains in historic paint media
• 400 nm stains in untreated wood
• 400 nm historic watercolours and inks
• 405 nm plastics without inherent UV protection
• 405 nm stains in historic textiles
• 405 nm protein structures (i.e. moist and dry preparations, leather, feathers, skin, hair)
• 405 nm stains in protein structures

50 Lux – a rating with little informative value

The gauging sensor of the light intensity gauges (luxmeters) was developed to attain values adapted to the brightness sensitivity displayed by humans.

The gauging sensor of a luxmeter was NOT developed to gauge absolute energy quantities!

For this purpose, there are spectrometers which – depending on the wavelength – can detect the corresponding energy quantity.

This aforesaid positioning of a luxmeter results in the display by the luxmeter of i.e. a certain quantity of energy at 550 nm (green light) with i.e. 50 Lux, while in the blue range of the spectrum, however - at i.e. 405 nm – an approx. 100-fold higher energy quantity hits the object, whereby the value of 50 Lux is also displayed here!

Do you remember the analysis performed by Judd and Hilvert?

At 405 nm, the relative damage factor according to Judd and Hilvert amounts to 60! Of course, at the same amount of energy as for 546 nm!

From this, one can conclude that if the luxmeter would display 50 lux (for a light source reflecting primarily in the blue range)...

...in fact, however, a 6,000-fold higher damage factor would apply!
(100-fold higher energy amount [to attain 50 lux] x 60-fold relative damage factor)

Perhaps you would agree with us that one should change the heading of this paragraph (in light of this correlation) to ""50 Lux – a misleading value""...

...at least when the 50-lux value is viewed in an isolated context.

An interesting observation in this context, too, is also that there are simple luxmeters on the market which only measure starting at 470 nm – that is to say, between 400 nm and 470 nm, this measurement structure would leave a disastrous measurement gap! After all, most of the simple UV gauges have a capacity which extends to 400 nm. In this context, the energy quantities in these UV gauges are only viewed in an integrative context and likewise weighted – mostly in such a manner that as a rule, they weight the energy less between 380 nm and 400 nm.

Auch diese Annahme stimmt nur zum Teil!

Man muß sich schon die Transmissionskurven der einzelnen Farbgläser im Detail ansehen!

Dabei muß man auch unterscheiden ob es sich um durchgefärbte Gläser oder Gläser mit einem Farbauftrag handelt.

Hier haben wir Ihnen einmal verschiedene Beispiele zusammengestellt.