Reflow oven according to the present invention includes a chamber housing, a chamber housing, the surface in contact with the heated air contaminant mixture comprising a flux and, provided with a selectively water-soluble layer which is applied to the surface of the chamber housing to. Embodiment of the reflow oven include an acryl-based layer, such as acrylic paints. In one embodiment, the acrylic paint include water-soluble polymers, polymer emulsions and water. The water-soluble polymer comprises a butyl benzyl phthalate. In some embodiments, the acrylic paint and 1 to 10% by weight butyl benzyl phthalate, an acrylic polymer emulsion to 30 to including 55%, and the balance of water. In certain embodiments, the acrylic paint and comprises a butyl benzyl phthalate and 1-5% by weight, water acrylic polymer emulsion 35 to 50% by weight, and the glass part. Method of processing a surface of a reflow oven is also disclosed.