This is a cross post - What technique can you use to remove the yellow tint to old decals. I’m working on the old Aurora Wanderer Whaler and while the decals look solid, the white lettering is yellowed from age. My alternative is to use dry transfer decals from Woodland Scenes. The whale boats have black lettering, which I’m trying for verify they even put names on the whaleboats or was that something Aurora came up with.
Thanks.
Nothing, once they yellow they are trash.
Steve
Sometimes, this isn’t always a fix, you can put them in a window 
that gets a good amount of sunlight. Leave it in a spot in the window where it won’t get damaged for a few days to a week or so. I have had some that it worked on and I have had some that it didn’t. If it works, I would also spray it with a clear coat or a clear varnish. Many decal sets get brittle when they get older. The clear should keep the decals from splintering on you when you try to apply them. I hope this helps.
Thank you, that what I was looking for, I just could remember how to do it.
Thanks mate - I’ve got an older Hasegawa kit in the stash whose decals have experienced some yellowing - I’d heard about leaving them in the sunlight to cure the yellowing, but I didn’t think about how brittle they might become. This is particularly significant for this kit, because if memory serves me correctly from building it in my teens, I’ll need to actually cut out the centre of the arrow painted around the exhaust tubes
Hanging them in a window did nothing for me.
Steve
I’ll second the bleaching with sunlight in the window, with a couple cautions.
First, put the decals in a small ziploc bag, this keeps them from interacting with any moisture near or on the window. I usually tape the bag to a south facing window for this.
Second, don’t forget about them. Check on them regularly, because while the yellowing is leaving, so too is some of the colour that you want to keep. I’ve forgotten a set on the window for a couple weeks and it was washed out so much that I couldn’t use them after. On the plus side, all yellowing was gone. 
Third, don’t forget about them again. I have no science or proof to explain what happened, maybe coincidence, but I once left a decal sheet for an extended period, attached to the glass. When I checked on them, they were completely colourless, but worse, the window seal had failed right below them. There was moisture between the panes and I had to replace the sealed unit. Was there a heat issue? Something else? I don’t know, but it was the only issue one any of the 5 new windows we had installed in the house that year.
Anyway, I would scan the decals first, so you can print new ones if needed, then give this a shot. Nothing to lose if they are already unusable due to yellowing.
Sometimes it works, sometimes it doesn’t. I did say that it doesn’t always fix it.
Yes I read that and I’m just stating that it didn’t work when I tried it.
Steve
I have never had success with the “sunlight-in-the-window” bleaching technique. My technique is to source new decals. I concede that not every subject done over the years has been redone by today’s decal makers. But for most subjects, I have been able to find new decals to use.
