Spectral profiles (observations in blue, inversion fit in orange) of a pixel from the region showing TBFs. The location of this pixel is given in Fig. 1 as a blue cross. Top row: Ca I 10 839 Å line, central row: Si I 10 827 Å line, bottom row: He I 10 830 Å triplet. All spectra are normalized to the quiet-sun continuum value. The spectra for pixels from other regions are shown in Appendix C.