I was dusting my built models recently, and was surprised to see that the decals on my 1/144 Hasegawa 747-400 (JAL Super Resort Express) had a turned a light brown color. Not just on a portion, the entire clear part of the decal I neglected to cut when applying it had also turned brown [:(!]. Looking over at my 1/72 Testors OA-4M Skyhawk, I saw that it too was devoloping this brown stuff.
Is this ?normal? (sun exposure) or am I screwing up somewhere?
Did you overcoat them with a clear finish after originally building the planes?
Yes, I spray them with either Testors Dullcote or Glosscoat as the final step in each model.
How old are they? Did you use the decal setting solution on them and not rinse the decalled areas with water afterward? I have noticed brown when I use decal setting solution immediately after they dried but they cleaned up with plain water applied with a brush or finger then towel dried. Overcoating will seal in the stain.