Examples of such wetting agent are polyalkylene glycols such as polyethylene glycol, polypropylene glycol etc.; alkylene glycols containing 2 to 6 carbon atoms such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol etc.; lower alkyl ethers of diethylene glycol such as ethyleneglycol methylether, diethyleneglycol methylether, diethyleneglycol ethylether etc.; glycerin; lower al