EXHIBIT 10WW
                                                                    ------------

                     ADVANCED DEPOSITION TECHNOLOGIES, INC.
                         Myles Standish Industrial Park
                          Taunton, Massachusetts 02780


                                                    Dated as of:  March 31, 2000

National Bank of Canada
One Federal Street, 27th Floor
Boston, Massachusetts  02110

         Re:  Modification No. 6 to Revolving Credit and Term Loan Agreement
              --------------------------------------------------------------

Ladies and Gentlemen:

         We refer to the Revolving Credit and Term Loan Agreement, dated as of
July 8, 1996 (as from time to time amended and in effect, the "Agreement"),
between Advanced Deposition Technologies, Inc. (the "Borrower") and National
Bank of Canada (the "Lender"). Terms used in this letter of agreement which are
not defined herein, but which are defined in the Agreement, shall have the same
respective meanings herein as therein.

         We have requested you to waive certain financial covenant defaults and
to make certain amendments to the Agreement. You have advised us that you are
prepared and would be pleased to waive the defaults and make the amendments so
requested by us on the condition that we join with you in this letter of
agreement.

         Accordingly, in consideration of these premises, the promises, mutual
covenants and agreements contained in this letter of agreement, and fully
intending to be legally bound by this letter of agreement, we hereby agree with
you as follows:

                                    ARTICLE I
                                    ---------

                             AMENDMENTS TO AGREEMENT
                             -----------------------

         Effective as of March 31, 2000 (in this letter of agreement, the
"Modification Date"), the Agreement is amended as follows:

         (a) The term "Loan Documents" shall, wherever used in the Agreement or
any of the other Loan Documents, be deemed to also mean and include Modification
No. 6 and all (if any) other documents executed and delivered in connection
therewith.

         (b) The Lender hereby exercises its discretionary right under Section
5.1(vi) of the Agreement to require that Borrowing Base Reports be hereafter
delivered within three Business Days after the close of each one-week fiscal
period of the Borrower, and the Borrower hereby acknowledges and agrees to the
foregoing (it being understood, however, that so-called backup journals may
continue to be delivered on a monthly basis).

         (c) The following two new definitions are added at the end of Section
1.1 of the Agreement:

            "Modification No. 6" means that certain letter agreement dated as of
March 31, 2000 between the Borrower and the Lender, upon the terms of which the
Agreement was further modified and amended.

            "Sixth Modification Date" means March 31, 2000.

         (d) Section 5.16 of the Agreement is amended to read in its entirety as
follows:

             "[Intentionally Omitted.]"


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         (e) Section 5.20 of the Agreement is amended: (i) by deleting the
reference therein to "$2,000,000", and (ii) by inserting in place thereof the
following: "$1,500,000".

         (f) Section 6.1 of the Agreement is amended by adding the following new
event of default at the end thereof:

                  "(xviii) the failure of Alexander Peter Boxall to provide the
         Borrower with a subordinated loan of at least $300,000 in cash by April
         15, 2000, the terms of which loan (including, without limitation, the
         terms of subordination) shall be satisfactory to the Lender in its sole
         discretion."


                                   ARTICLE II
                                   ----------

                                     WAIVER
                                     ------

         We have informed you that the Borrower is not in compliance with
Section 5.14 of the Agreement with respect to the fiscal year ending December
31, 1999, which constitute separate Events of Default under (and as defined in)
Section 6.1(i) thereof. The Borrower has requested that the Lender waive the
foregoing Events of Default.

         In accordance with such request, the Lender hereby waives the foregoing
Events of Default. This waiver is limited solely to the foregoing Events of
Default as of December 31, 1999, and March 31, 2000, respectively, and shall not
extend to any other period, any other provision of the Agreement or any other
Default or Event of Default which may now exist or hereafter arise under the
Agreement.

         It is understood and agreed that the covenant contained in Section 5.14
shall continue to be in full force and effect.


                                   ARTICLE III
                                   -----------

                         REPRESENTATIONS AND WARRANTIES
                         ------------------------------

         The Borrower represents and warrants to you as follows:

         (a) Representations in Agreement: Each of the representations and
warranties made by or on behalf of the Borrower to you in the Agreement or any
other Loan Document, as amended through this letter of agreement, was true and
correct when made and is true and correct on and as of the Modification Date
with the same full force and effect as if each of such representations and
warranties had been made by the Borrower on the date hereof and in this letter
of agreement, except to the extent that such representations and warranties
relate solely to a prior date.

         (b) No Events of Default: No Default or Event of Default exists on the
Modification Date (after giving effect to all of the arrangements and
transactions contemplated by this letter of agreement).

         (c) Binding Effect of Documents. This letter of agreement has been duly
executed and delivered to you by the Borrower and is in full force and effect as
of the date hereof, and the agreements and obligations of the Borrower contained
herein and therein constitute legal, valid, and binding obligations of the
Borrower enforceable against the Borrower in accordance with their respective
terms.

                                   ARTICLE IV
                                   ----------

                        PROVISIONS OF GENERAL APPLICATION
                        ---------------------------------

         (a) No Other Changes. Except as otherwise expressly provided by this
letter of agreement, all of the terms, conditions and provisions of the
Agreement and each of the other Loan Documents remain unaltered. The Agreement
and this letter of agreement shall be read and construed as one agreement.
Except to the extent specifically amended hereby, the provisions of the
Agreement shall remain unmodified, and the Agreement, as amended hereby, is
hereby confirmed as being in full force and effect, and the Borrower hereby
ratifies and confirms all of its agreements and obligations contained therein or
in the other Loan Documents.

         (b) Governing Law. This letter of agreement is intended to take effect
as a sealed instrument and shall be deemed to be a contract under the laws of
the Commonwealth of Massachusetts. This letter of agreement and the rights and

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obligations of each of the parties hereto shall be governed by and interpreted
and determined in accordance with the laws of the Commonwealth of Massachusetts.

         (c) Binding Effect; Assignment. This letter of agreement shall be
binding upon and inure to the benefit of each of the parties hereto and their
respective successors in title and assigns.

         (d) Counterparts. This letter of agreement may be executed in any
number of counterparts, but all such counterparts shall together constitute but
one and the same agreement. In making proof of this letter of agreement, it
shall not be necessary to produce or account for more than one counterpart
thereof signed by each of the parties hereto.

         (e) Conflict with Other Agreements. If any of the terms of this letter
of agreement shall conflict in any respect with any of the terms of the
Agreement or any other Loan Document, the terms of this letter of agreement
shall be controlling.

         (f) Conditions Precedent. This letter of agreement shall become
effective as of the Modification Date, but only if:

             (i) the form of acceptance at the end of this letter of agreement
         shall be signed by the Lender; and (ii) the Lender shall have received
         from the Borrower payment of a non-refundable amendment and waiver fee
         in the amount of $30,000.

         If you are in agreement with the foregoing, please sign the form of
acceptance on the enclosed counterpart of this letter of agreement and return
such counterpart to the undersigned, whereupon this letter of agreement, as so
accepted by you, shall become a binding agreement between you and the
undersigned.
                                          Very truly yours,

                                          The Borrower:
                                          -------------

                                          ADVANCED DEPOSITION TECHNOLOGIES, INC.

                                          By:  /s/  Joseph Keller
                                               ----------------------------

                                          Title: Controller
                                                 --------------------------

                                          By:  /s/  Alexander Boxall
                                              -----------------------------

                                          Title:   President
                                                 --------------------------





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         The foregoing agreement is hereby accepted by the undersigned as of
March 31, 2000.

                                          The Lender:
                                          -----------

                                          NATIONAL BANK OF CANADA


                                          By:  /s/  A. Keith Broyles
                                               ----------------------------

                                          Title: Vice President and Manager
                                                 --------------------------

                                          By:  /s/  Leonard J. Pellecchia
                                               ----------------------------

                                          Title:  Vice President
                                                 --------------------------







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