 Water @-@ based lubricants , called emulsions , are the most commonly used type of lubricant , because of health , environmental , and safety reasons . Unlike solvent @-@ based lubricants , if water is properly treated to remove all minerals from it , it will not leave any by @-@ product in the dies . If the water is not properly treated , then the minerals can cause surface defects and discontinuities . There are four types of water @-@ based lubricants : oil in water , water in oil , semi @-@ synthetic , and synthetic . Oil in water is the best , because when the lubricant is applied , the water cools the die surface by evaporating while depositing the oil , which helps release the shot . A common mixture for this type of lubricants is thirty parts water to one part oil , however in extreme cases a ratio of 100 : 1 is used . 
