is not perfect as a practical matter but is usually in the range of about 10 to about 100 microns preferably about 10 to about 40 microns the temperature in step b is simply the condensation temperature of the vapors generally the temperatures used are in the range of about 20 u00b0 c to about 100 u00b0 c preferably about 20 u00b0 c to about 30 u00b0 c the various zones in the parylene deposition system are usually provided for in separate chambers one for vaporization of the dimer and the phenol or pyrogallol where this means is used for introducing these compounds one for pyrolysis one chamber for the vaporization of the phenol where these compounds are to be introduced by leak valve and one chamber for deposition examples of preferred sterically hindered phenols are 2 6 dimethyl phenol 2 6 di tert butyl 4 methyl phenol 2 6 di tert butyl 4 n butyl phenol an example of a compound which yields a vaporizable sterically hindered phenol on heating also preferred is 1 1 3 tris 2 methyl 4 hydroxy 5 tert butyl phenyl butane other sterically hindered phenols useful in the article and process may be represented by the following general structures str3 wherein r 39 and r 34 are alike or different and are alkyl radicals having 1 to 5 carbon atoms these radicals are preferably the same r 34 39 is hydrogen or an akyl radical having 1 to 5 carbon atoms r 39 and r 34.