Stare at my hands and dare them to speak
[I'm a connoisseur of first lines and this one is excellent.]
the scars that blink as they move
[This line I didn't quite get the blinking image. Unhealed cuts can be seen to open and close, but scars blinking?]
tri-tone paint splattered callouses
[Does tri-tone have significance? Or are you just talking about paint on hands?]
mix with fresh cut skin
[Maybe this answers my blinking query, cut skin and all.]
Fingers thick and clumsy
beaten and moulded
by heavy weights, hard work
and hours of hitting a heavy bag
[You've already shown us the character is a hard worker. There's no need to actually say it out loud.]
they have punched brick
smashed plasterboard
one knuckle still in two
from an errant tooth
in a bar room brawl
[Two/Tooth nice partial rhyme, so far your sound elements have barely teetered you away from prose. Alliteration is kind of the last outpost from the tradition. I think they still weed out accidental alliteration from novels in editing.]
the story they most want to tell
is the day they held you
gentle
and shaking wept
for fear they were too clumsy
to hold your fragility
a triumph as we cradled you
to our heart
[I feel like a comma or change in break is necessary somewhere between "held you...too clumsy". Repetition of "clumsy" seems like a missed opportunity, it's an identical meaning. The "we" is out of place, this third other is awkwardly introduced when the entire poem was a 'from me to you' not quite Lennon/Mccartney reflection.]
....
'Triumph' is a good word, Sign Language is a good poem. My main issue is that the one being spoken to/of isn't aware of the details of the hands, can't begin to wonder about their character. So the poem exists for some future grown baby to unlock and has a great deal to offer that individual in sentimentality while right now it offers me very little emotively. As a father I would be happy to leave such a nice poem for my grown children.
To conclude:
Foehn's narrator wrote a poem about and for his daughter, so as a reader I was able to share with him the joy of fatherhood at face value and also a separate unbridled joy in his experience of loving some-thing wholly un-pin-a-down-able. Sign Language is fairly polished, it's fine as is really. If you ask me is it a good poem, I've answered that. If you're interested in why it's not a great poem, I don't think I could answer that.