There is an increasing interest in manned solar balloons which uses sunlight instead of propane to heat the air inside the enveloppe. A black balloon is simple to build but rather inefficient : only a small volume near the enveloppe is heated and half the energy received is lost as it heats the outside air. To remedy the problem, I took inspiration from my stratospheric soot injector and filled the transparent enveloppe with sunlight-absorbing artificial smoke.