What the hell is handoiled paper?

Good evening everyone!

While having a glass and a thimble of a delicious red wine, the firefly kept its promise and explained what the baby oil is for! That meant three and a half hours of paper, translucence, rubber ducks and different types of oil for me - and please don’t ask, what rubber ducks have got to do with it. Nothing! Absolutely nothing! My tiny friend just cannot stay on the track.

I try to summarize the important facts of this lesson for you:
Mostly, the firefly uses a kind of drawing paper (that is “Tonpapier” in German, I’m not sure about the correct English term) for its fairy lights. But before it starts to work with the paper, wacky-wing-that-must-not-be-interrupted lubricates it with baby oil (It tried other types, but as it puts it: “I don’t want to work in a @#!?# olive grove, and I’m sure a lot of people don’t want one in their sitting rooms!”).
Then the oil has to dry for three or four days - and that explains why our floor is always covered with paper sheets and I have to walk zigzag through our home. Easy task, when you have wings...

Nearly two hours later we finally reached the gist of the matter.
There are basically two reasons: First, the oil makes the paper more heat-resistant. At this point the little idiot nearly burned down the house to demonstrate it  - Promise me, that you NEVER try that!
Secondly, it’s a question of translucence. I added some pictures, to give you a better idea of what I mean. When the paper is oiled, the color darkens, as you can the on the first picture with the two different sheets. In fact, both sheets have the same color. The left (bright) sheet is not yet oiled, while the right (dark) one is: 

Left side: "normal" paper; Right side: "unnormal" paper

Light behind unoiled paper

Even though the paper becomes darker, the light effect becomes much more impressive. You can see the difference on the second and third picture.

same light, same paper + oil

There you go! That’s the whole secret!
I learned a lot of interesting things today (and a lot of crap) and now I have to put a little, drunken firefly to nest ;-)