Unable to convert blob to text

So recipe is a blob column, i was trying to read this blob data. Tried SQL Developer

select utl_raw.cast_to_varchar2(dbms_lob.substr(recipe,4000,1)) from RMS_PNG.RMS_GOLDENRECIPE where toolid = 'DEK-04' and recipeid='31018';

ORA-06502: PL/SQL: numeric or value error: raw variable length too long

ORA-06512: at line 1

06502. 00000 - "PL/SQL: numeric or value error%s"

*Cause:  An arithmetic, numeric, string, conversion, or constraint error

      occurred. For example, this error occurs if an attempt is made to

      assign the value NULL to a variable declared NOT NULL, or if an

      attempt is made to assign an integer larger than 99 to a variable