In order to examine the skin types for you and for us in detail, we spared no expense and efforts and made an interesting experiment. We packed 4 interns in a plane and sent them to the equatorial island of Bali: James from North Ireland, Julia from Germany, Julie from France and Giulio from the south of Italy. Once there, we put our subjects in four sun loungers on the beach in the sun and pressed a Balinese employee of the hotel a stopwatch in the hand, who lingered in the shade of a palm tree. He started to take the time.

Let´s see how long it will take for sunburn to set in.

The stopwatch showed no more than 10 minutes and the red-haired James, visibly sweaty, already left his sun lounger and sought protection from the sun. 6 minutes later, blonde Julia wiped the drops from her forehead and followed James. Julie stayed in the sun until the 29th minute passed, brushing her brown hair out of her face and also disappearing. All alone, the black-haired Giulio began to get bored and went out of the sun after a total of 45 minutes – he was thirsty and did not want to be alone on the beach. The Balinese pressed the last time on the stopwatch…and wondered what was going on there. Experiment done!

Well, let´s be honest…it was just a thought experiment – because of all the time we invest in Julie Soléy we only had the time to do the experiment mentally.

But what does this thought experiment show us?

The experiment illustrates the characteristics of the four different skin types classified by the American dermatologist Thomas Fitzpatrick in 1975, which are still valid today. For the sake of completeness, it has to be said that in the classification he referred to the so-called “white skin type” and later added two other types: the dark-skinned and the black skin type. However, these two are not as relevant to our study on sunscreen and therefore do not occur in our mental test setup. In the following, let´s consider the skin types one to four, to which Fitzpatrick attributed the following properties.