This image was a normal photo enlarged on Kodak Ortho film instead of paper. This produced a positive image on the film of black and clear, there are no mid tones with ortho film. A contact exposure was made with a second sheet of film which resulted in an ortho negative of the image the same size as the positive. The 2 pieces of film were then taped together slightly a skew of each other so that only a little light would get through. This positive/negative film combination was then placed into the enlarger and projected on Grade 5 enlarging paper to assure there would be no gray tones. The result is what you see. No photoshop or digital techniques were used at all in this image, this is what it looks like on the paper. That was the way it was done in the olden days before computers. To vary the thickness of the lines all you have to do is shift the negatives in relation to each other and more light will go through.
Yep Phillip I know of the process... my broken windows was done basically the same way except for the grade 5 paper... love the effects.. simply love it...... Hooray for the darkroom.....