Polymer clay UV light fastness trial

For some time I have felt it is a shame that I cannot sell my polymer clay mosaics/creations for outdoor use, as the colours will fade if exposed long term to sunlight. How much and how quickly this will happen, I do not know, so I have decided to set up a trial. I wanted to get this going now, as we are just entering the summer months (in New Zealand) and our sunlight is extremely harsh, so it will be a good test.

I am currently using the New Zealand made brand of polymer clay, called Du-Kit, as it has been hard to get Sculpey Premo (my prefered brand) since the Covid Lockdowns. To save mixing colours, I am using the ends of some canes that were made for a project, which have a range of colour blends within a particular hue (shown to the left in the photo below). I have also included some neutral colours (shown to the right in the photo below): black, grey made from 50% black and 50% white, white, pearl, transluscent and Super Sculpey (grey). 

The polymer clay tiles have been stuck and grouted to the back of a couple of ceramic wall tiles, as this was all that I readily had to hand. 

The top half of the coloured tiles have been masked off with opaque black plastic tape. I am hoping this will hold up to the long term effects of the weather.

There are two rows of tiles in the neutral colours. The top half of the top row has been masked off with opaque black plastic tape. The bottom row has been used to test UV protective varnish; the upper half of the bottom row has 2 layers of Josefine Very Matt Varnish and the bottom half has 2 layers of Josefine Satin Varnish.

Today (12th December 2021) I have placed the trial tiles on the bottom rail of the garden fence that gets plenty of sunshine during the day.

I plan to check how much colour fading has occurred after 1 month, 3 months, 6 months and 12 months. Then, depending on the results, I may continue to monitor.