curing fluorinatedpolyimide based treating solutionsstart endtemperature rate temperature hold______________________________________65 u00b0 c 240 u00b0 c 25 u00b0 c hour 240 u00b0 c 4 hours______________________________________ it may be necessary where a very low degree of porosity is required to repeat one or more times the cycle of applying coat of treating solution removing excess solution and curing the solution a 34 finish 34 coating may be applied to the impregnated carbon or graphite article after curing which serves to fill any residual porosity and to level the article surfaces in one embodiment using furan based treating solutions the resin impregnated surfaces of the article are heated to an elevated temperature which is below the polymerizing temperature of the resin in the presence of the catalyst i e about 45 u00b0 c in the case of the preferred furfuryl alcohol zinc chloride system the heated resin impregnated surfaces of the article are then coated uniformly with a layer of the treating solution after which the surface is hand burnished with a damp cloth during the burnishing the polymerization may advance due to the heat in the article which may be further heated to assist further polymerization of the resin by hand burnishing it is possible to produce a thin level glassy surface film on the article.