If your HDU sign foam takes more than one coat of primer you should try Duna Corafoam.
The average cell diameter of Duna Corafoam is smaller and more evenly distributed than other sign foams. The average cell diameter of Duna Corafoam is 55 microns. Other brands of sign foam average 65 to 90 microns. This is why many customers tell us that they use Duna Corafoam because it takes less primer.