uniformly dispersed that when it melts it forms a very thin but substantially continuous coating on the outer surface of the preform that is in contact with the lubricant this inhibits the lubricant iron interaction previously referred to on the preform also an increase in lubricity may be an added benefit on the other hand the amount of copper present is insufficient to deleteriously alter the predetermined metallurgical properties of the hot formed article even at its surface the resultant article appears as if no copper were present in the lubricant and no subsequent treatment is necessary because the copper powder was used in the lubricant a powder of pure copper is preferred however the term copper powder is also intended to include any copper alloy having more than 50 copper and having a melting point temperature less than about 2000 u00b0 f at least about 2 by weight of copper powder having a particle size of the order of about 15 microns seems necessary in the diluted lubricant the lubricant as used to insure that the lubricant iron interaction on the preform is suppressed if the copper powder is included in the concentrated lubricant the minimum weight percent copper powder to be included will vary depending on the extent to which the concentrated lubricant is to be diluted for example if one part of the colloidal graphite concentrated lubricant contains 30 by weight solids and lubricant is to be diluted with thirteen parts of a diluent at least about 21 by weight copper powder should be included an equivalent dilution of a colloidal graphite concentrated lubricant containing only 10 by weight solids on the other hand would require only about.