EXHIBIT 32 CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350, AS ADOPTED PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002 Pursuant to 18 U.S.C. Section 1350 as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, each of the undersigned certifies that this periodic report fully complies with the requirements of Section 13(a) or 15(d), as applicable, of the Securities Exchange Act of 1934 and that the information contained in this annual report on Form 10-K fairly presents, in all material respects, the financial condition and results of operations of Spartech Corporation. Date: January 12, 2005 /s/ Bradley B. Buechler Bradley B. Buechler Chairman, President and Chief Executive Officer /s/Randy C. Martin Randy C. Martin Executive Vice President and Chief Financial Officer