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Can you wash away UV-absorbing material?


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#1 nfoto

    Former Fierce Bear of the North

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Posted 12 April 2013 - 22:22

Every keen UV photographer sooner or later makes a shot to show the impact of UV-screening material such as sun lotions. You can make hidden messages to be revealed by UV photography, for example.

An interesting question is how efficiently can such material be removed? To be specific, can a healthy cleaning with a household detergent remove all traces of say a sun lotion. Here is a demonstration to show how persistent the UV absorbing material can be.

A white-painted door leaf was inscribed with ordinary Factor 10 Sun Lotion. Afterwards, the door was scrubbed using a strong solution of household detergents in warm water three times.

Photography using D40, Coastal Optics 60 mm f/4 APO lens, SB-140 flash.

Here are the results.First, visible light appearance:

Attached Image: DOOR_J0801270190_VIS.jpg

Then, the UV capture before cleaning.

Attached Image: DOOR_J0801270189_UV.jpg

The door was cleaned thoroughly once:

Attached Image: DOOR_J0801270194_UV_Cleaned_once.jpg

It is readily apparent that sun lotion does not wash off easily. Also note hand abnd palm prints still being visible.

After three cycles of cleaning, the message is still there.

Attached Image: DOOR_J0801270197_UV_Triple_Cleaned.jpg

The lesson for the UV photographer is to keep any sun screening material far away from his photographic gear.

[Published 13 Apr 2013]