Black And White Negatives Without Half - Tones. Such are caused by under - exposure; by the contamination of the nitrate bath after long use; by using a collodion that is too old and red; too much acid in the negative bath; too strong a developer; and, finally, by boiling your nitrate bath to fusion. A great many recommend this latter method to get rid of organic matter in the bath, and yet so few know how to do it properly. If it is fused beyond a certain point, solarization of the nega-tiws is sure to result, and you get chalky whites and deep blacks without detail or half-tones.