plotting – List of interpolation functions

I generate a list of interpolation functions indexed by a real variable ki

Do[f[ki] = Interpolation[A[ki]], {ki, kData}]

Next, I define

f3d[k_, w_] := f[First[Nearest[kData, k]]][w]

Next, I would like to DensityPlot

DensityPlot[f3d[k,w],{k, 0, 10}, {w, -5, 10}]

But I get an empty plot. On the other hand f3d[3.5][5.5] works fine. Probably I am missing something obvious…