Finally we organized results of Yellowing test and want to share the result with you all.

The upper torso was exposed on direct sunlight, outdoor, for 30 days.

As you can see by the result, skin color has turned yellow but it didn't turned green or changed dramatically. At first, red color vanished slowly and after some time color started to turn yellow. And after 30 days, there was no more color change so we stopped the experiment.

At first red color vanishes slowly and then start turning yellow after quite a long time. Also even a very light, thin cloth can block UV so if you keep your doll dressed or put a cape, it will be very helpful from preventing yellowing. Finally air is another factor which accelerates yellowing. So if you keep the doll in a box and store it in a dark place, it will prevent from turning yellow.

If you have any other question regarding the experiment, please leave a message on Q&A board.