The propagation threshold power through a white tight-buffered single-mode optical fiber was found to be 3% less than that through a transparent acrylate-coated fiber. This is because the white pigments in the buffer layer backscatter the visible emission that pumps a fiber fuse. Namely, the backscattered light is absorbed by the thermal decomposition product SiO in the glass melt surrounding the traveling plasma. This self-pumping effect was revealed by comparing the void trains left in fiber segments coated with white or black oil paint. This threshold reduction compels us to re-examine the power tolerance design of optical networks and fiber fuse terminators.