SQL & PL/SQL

Hi guys!
I have a picture in a blob column. I convert the blob to clob and insert it in clob column. After that I convert the clob again to blob, but the new blob is not my picture :(
My code blob to clob:
declare
v_pic BLOB;
v_clob CLOB;
v_dest_offset INTEGER := 1;
v_src_offset INTEGER := 1;
v_charset NUMBER;
v_lang_context NUMBER := dbms_lob.default_lang_ctx;
v_warning NUMBER;
BEGIN
dbms_lob.createtemporary(v_clob, TRUE, 2);
SELECT nls_charset_id('AL32UTF8') INTO v_charset FROM dual;
SELECT VALUE INTO v_pic FROM slavi_blob;
dbms_lob.converttoclob(v_clob,
v_pic,
dbms_lob.lobmaxsize,
v_dest_offset,
v_src_offset,
v_charset, --dbms_lob.default_csid,
v_lang_context,
v_warning);
insert into slavi_clob values(v_clob);
end;


Clob to blob:

declare
v_clob CLOB;
v_blob BLOB;
v_dest_offset INTEGER := 1;
v_src_offset INTEGER := 1;
v_charset NUMBER;
v_lang_context NUMBER := dbms_lob.default_lang_ctx;
v_warning NUMBER;
BEGIN
select value into v_clob from slavi_clob ;
dbms_lob.createtemporary(v_blob, TRUE, 2);
SELECT nls_charset_id('AL32UTF8') INTO v_charset FROM dual;
dbms_lob.converttoblob(v_blob,
v_clob,
dbms_lob.lobmaxsize,
v_dest_offset,
v_src_offset,
dbms_lob.default_csid,
v_lang_context,
v_warning);
INSERT INTO slavi_blob VALUES (v_blob);

end;

Best regard, Slavi