What makes dye go bad?

[masterplater]

I premixed the dye, and then use it, and return it back to the original container. Recently I anodized some parts, when I put them in the red dye
and it wouldn't take, thinking it wasn't anodized, I stripped it an reanodized it, after rinsing and putting it in the red dye again it still wouldn't take, I had some blue dye warmed up and low and behold it dyed beautifully. What was wrong with the red dye, is there a certain
timeframe in which it is good? I have red, electric blue, green, and violet.
I have used all the colors, violet the most, with excellent results. What gives with the deep red dye?

Thanks

[dropride]

i have used the red dye many times among others, as far as i know the dye doesnt go bad unless it is contaminated from some of the acid