This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
Such parts of a camera that are apt to reflect light must be covered with a dull black. A mixture for this purpose is made of lampblack, about a teaspoon-I'ul, and enough gold size to make a paste as thick as putty. Add about twice the volume of turpentine and apply to the parts with a camel's-hair brush.
As the turpentine fumes are detrimental to the sensitive plate, the camera should be left open until these fumes have entirely disappeared.