Animation-delay function not working on text (opacity)

I'm trying to make an animation-delay on my animation. The animation is used on some text, and the animation-delay line doesn't seem to work.

Here is the code :

.wtitle {
opacity:100%;
animation-name: afade;
animation-duration: 1s;
animation-delay: 15s;
}

@keyframes afade {
from {
    opacity:0;
}
to {
    opacity:100%;
}
}

Does anyone have an idea ?