I've been printing some signs on white coated metal. 2 colors. Nazdar 59-000 series enamel blue and LF Red.
Now I'm told they've been fading after about 6 months outside.
Using 305 mesh on both colors.
You guys know of a way to prevent the fading so soon?
305 is too tight a mesh for enamel really (we rarely print enamels with finer than 156). If you print out your image with that on a clear sheet of plastic and old it up to the light you will see that there is almost no ink there. Reds fade faster than other pigments generally. As Andy says a UV protectant would help. There are a lot of these of the market just make sure it sticks to enamel and they don't block all UV but the thicker you lay these down the more they will protect. Take a look at at adhesive vinyl for plotters you will see that there is a huge variation in what they will guarantee in direct sunlight.
We have even had metallic inks with pure metal pigments fade in direct sunlight.