  To date, the quasar 1556+3517 is the only radio loud Broad Absorption Line
QSO (BALQSO; Becker et al. 1997). This prompted narrow band filter imaging
observations in the range 4-15 micron with the ISO satellite. The source is
clearly detected in all filters and appears point-like and isolated at the
resolution of ISO. The overall Spectral Energy Distribution (SED) in erg/s
peaks at a rest wavelength > 6 micron and is reddened by 1.6 visual magnitudes.
Correction for reddening brings 1556+3517 within 1.3 sigma from the log R = 1
dividing line between radio-loud and radio-quiet sources. The mid-IR luminosity
integrated over the 1.8-6 micron rest wavelength range is ~ 2 E+46 erg/s (Ho =
75 km/s/Mpc, qo = 0), which requires at least 4 solar masses of dust and 800
solar masses of associated gas. It is unlikely that such a large mass stems
from the BAL wind itself.
