Exhibit 10.18
               

                               STOCK PUT AGREEMENT


         THIS STOCK PUT AGREEMENT (this  "Agreement") is made as of the 30th day
of September,  1996 (the "Effective Date"), by and between Exsorbet  Industries,
Inc., an Idaho corporation  ("Exsorbet") and American  Physicians Service Group,
Inc., a Texas corporation ("APS").

                                    RECITALS:

         WHEREAS, APS has purchased 1,200,000 shares of the common stock of 
          Exsorbet; and

         WHEREAS,  Exsorbet  desires  to allow  APS to cause  Exsorbet,  at APS'
option for a period of sixty (60) days,  to purchase  APS'  holdings of Exsorbet
stock;

         NOW,  THEREFORE,  in  consideration  of the  foregoing  and the  mutual
covenants and agreements contained herein, the parties hereto agree as follows:

         1.  Shares  Subject  to this  Agreement.  The  shares  subject  to this
Agreement are up to 1,200,000 shares of the outstanding common stock of Exsorbet
held by APS, including any increases,  decreases or substitutions therefor which
occur after the date hereof as a result of any change (through recapitalization,
merger, consolidation, stock dividend, stock split, combination,

                                        1

<PAGE>



reverse  stock split or exchange of shares or  otherwise)  in the  character  or
amount of such shares prior to the exercise by APS of its rights hereunder.

         2. Option to Sell. Exsorbet  irrevocably and unconditionally  grants to
APS the right,  privilege  and option to sell to Exsorbet  and  Exsorbet  hereby
irrevocably and  unconditionally  agrees to purchase,  the Shares, for the price
and on the terms provided herein.  This option can be exercised by APS notifying
Exsorbet in writing of the intent to exercise the option, in which case Exsorbet
will have ten (10) days to complete  the  purchase as  required  herein.  In the
event  the  parties  cannot  agree  on a time and  place  for a  closing  of the
purchase, the closing will occur at the offices of APS in Austin, Texas, at 1:00
p.m.  Austin  time on the tenth day after APS has given  notice of  exercise  to
Exsorbet.

         3. Purchase  Price and Payment.  The total purchase price to be paid by
Exsorbet for all the Shares is $3,300,000,  or $2.75 per share for purchase of a
portion of the Shares. The total purchase price shall be paid at closing in cash
or certified funds or by execution and delivery by Exsorbet of a promissory note
(the "Note") payable to the order of APS in the original principal amount of the
purchase price in the form of Exhibit-A  hereto. In the event Exsorbet elects to
pay for the Shares by execution and delivery of the Note,  APS shall be entitled
to retain a  first-lien,  perfected  security  interest in and to the Shares (in
addition  to  whatever  other  collateral  may  be  used  to  secure  Exsorbet's
obligations  hereunder  as  contemplated  in  Section 5 below)  and APS shall be
entitled  to retain  possession  of the  certificates  evidencing  the Shares to
perfect such security interest.  In the event the purchase price is paid in cash
or certified funds, or upon payment in full of the Note and

                                        2

<PAGE>



all  interest  due  thereon,  APS shall  deliver to  Exsorbet  all  certificates
representing the Shares sold, duly endorsed to Exsorbet.

         4. Assignment.  This option and the rights granted under this Agreement
may be transferred or assigned by APS to any affiliate or subsidiary of APS. 
Otherwise, the rights and obligations of the parties under this Agreement may
not be assigned or transferred without the express prior written consent of the 
other party.

         5. Obligations of Exsorbet  Secured.  The obligations of Exsorbet under
and pursuant to this Agreement  shall be secured by that certain  Assignment and
Security  Agreement of even date herewith  pursuant to which  Exsorbet  grants a
security interest in certain collateral to APS to secure Exsorbet's  obligations
under this  Agreement.  In  addition,  the  obligations  of  Exsorbet  under and
pursuant to this Agreement are further guaranteed by the payment and performance
guarantees of each of Exsorbet's subsidiaries.

         6. Insufficient  Surplus. In connection with the purchase of any Shares
by Exsorbet  pursuant to this Agreement,  if the surplus of Exsorbet shall prove
to be  insufficient  under then existing laws to allow  Exsorbet to purchase all
the Shares which APS then elects to sell to  Exsorbet,  Exsorbet  shall,  within
sixty (60) days of receipt of APS's written  notice of intent to exercise  their
option to sell Shares hereunder, take such action, execute such instruments, and
otherwise  do whatever  may be  necessary  to increase  its surplus to an amount
sufficient to authorize  the purchase of such Shares,  including but not limited
to, one or more of the following:

                                        3

<PAGE>



                  (a)      a recapitalization of Exsorbet so as to reduce its 
                           capital and increase its surplus;
                  (b)      a  reappraisal  of the assets of  Exsorbet  including
                           goodwill, if any, to reflect the market value of such
                           assets on the  books of  Exsorbet  in the event  such
                           value  exceeds  the  book  value  thereof,  so  as to
                           increase such surplus; or
                  (c)      any and all other means or procedures as permitted by
                           law.

         7.       Notices.  All notices required to be given hereunder shall be 
                         deemed to be duly given by personally delivering such 
                         notice or by mailing it certified mail to all parties 
                         hereto at the following address:

         Exsorbet:        Exsorbet Industries, Inc.
                          1401 South Waldron, Suite 201
                          Fort Smith, Arkansas 72903
                          Attn: Charles E. Chunn, Jr.

         APS:                       American Physicians Service Group, Inc.
                                    1301 Capital of Texas Highway, Suite C-300
                                    Austin, Texas 78746-6550
                                    Attn: President

         The foregoing  addresses may be changed by providing  written notice of
such change of address by certified mail to the other parties to this Agreement.

         8.       Exercise of Option.  This option shall be exercisable at any 
                   time or times until sixty (60) days after the Effective Date.
                   Upon expiration of this time period, if APS has not exercised

                                        4

<PAGE>



its rights hereunder,  Exsorbet shall pay APS $60,000 within five (5) days after
the expiration of such sixty (60) day period.

         9.       Binding Effect.  This Agreement shall inure to the benefit of 
and be binding upon the parties hereto, and their respective successors and 
permitted assigns. Exsorbet may not assign this Agreement or any of its rights 
or obligations hereunder without the prior express written consent of APS.

         10.      Governing Law.  This Agreement shall be interpreted under the 
laws of the State of Texas, and all obligations created hereunder are 
performable in Travis County, Texas.

         11.      Further Assurances.  All parties hereto agree to perform any 
further acts and to execute and deliver any further documents which may be 
reasonably necessary or convenient to carry out the provisions of this 
Agreement.


                                        5

<PAGE>


         IN WITNESS WHEREOF,  the parties hereto have executed this agreement in
multiple counterparts in Austin, Texas on the day and year first above written.

         EXSORBET:                        EXSORBET INDUSTRIES, INC.



                                          By:

                                          Printed Name:

                                          Title:


         APS:                             AMERICAN PHYSICIANS SERVICE
                                             GROUP, INC.



                                           By:

                                           Printed Name:

                                           Title:



                                        6