Help with fading out the text?

Im doing a count down animation in Unity animator , with text mesh pro, the text is going from 3,2,1 to 0 . When the text goes from one number to the next Im trying to do fade out the number with setting the alpha to 0 at the next number switch key, but it doesnt seem to work. Im using text mesh pro... Do I need to turn something on, or is the fade out not doable in the Unity animator ? thx