noun. In pin-manuf., the operation of boiling the pins in an acid solution preparatory to nurling or tinning.

noun. A pathological condition of plants in which the leaves become yellow. It may be due to various causes, such as an excess of carbon dioxid in the air, an excess of water about the roots of the plant, or the presence of poisonous or acid gases in the soil or air.

noun. The act or process of making yellow.

verb. Present participle of yellow.

noun. The act of becoming yellow and/or of losing brightness

"The brown tinge of the paper, which we call yellowing because our eyes cannot believe in color, indicate that the paper is acidic, degrading."

bellowing  mellowing  

yellow