I've been restoring the bay windows on my 1940's. I've stripped the main frames back to remove the layers of paint which has built up over the years. I've primed and undercoated the frames and any gaps in between the five casements and the casements and the cill, I filled with Brewers external filler. That was about a month ago. I've just gone out to lightly rub down for a second undercoat and where I used filler has cracked open. See attached photos.
Is there a better flexible filler or do I have to use Decorators caulk?
Is there a better flexible filler or do I have to use Decorators caulk?