It sounds like someone was a smoker and that is the yellow haze. Generally the image is out of focus when it passes through the condensers and the yellow haze is reducing the contrast of the the negative. The only two places the image is in focus is at the negative stage and at the paper. IF you have hair or dust that is sharp that is where you need to look. What you don't want to do is handle the condesers a lot. They are easily damaged or chipped when you drop them. I took mine out and replaced the head with an Aristo VCL45. That is a two tube cold light. It is controled by a Metrolux II. Great combo.