As Fred says, 10% should be good to go for 1080. The oldschool mix it until an egg floats on top should come in around 10% or just higher. According to mete, 9% NaCl is the fastest mixture, but that shouldn't be necessary for 1080, in my opinion.
Also suggested to me today was dish soap instead of the salt. I've done this in the past, but don't have any data on a "proper" mixture for it.