“You can hold it over a little gas fire or an electric heater” he said, “but with a candle you can vary your effect from area to area much better. When you dip the plate into the acid bath again, all the little burst bubbles of resin protect those areas and the acid eats in between them where there is no resin. In that way you can bring out certain areas more clearly, and cause others to fall back into shadow, just as you protect others with varnish so that the acid doesn’t penetrate. This technique has a far wider range of subtlety than ordinary etching. This is how Goya, in his Desastres de la Guerra, obtained those marvelous blacks which are never opaque. "
                                                                                                                                                        Life with Picasso……….Francoise Gilot and Carton Lake