Degreasing metals by wetting with a solvent. Degreasing by wetting with a solvent is used for large surfaces of products, which cannot be immersed in the tub. This method is also used to locally soften the hard coating of the grease before it is rubbed off. This procedure is usually performed with a rag moistened with a solvent, preferably "PT” or perchlorethylene, which are less volatile than trichlorethylene. Degreasing large surfaces should be carried out in well-ventilated rooms, away from open flames due to the likelihood of decomposition of solvents. The resulting decomposition products have a strong toxic effect. Smoking is also prohibited for this reason.