<PAGE>

                                                                    EXHIBIT 4(e)

                  FOURTH AMENDMENT DATED AS OF APRIL 20, 2001
               TO CREDIT AGREEMENT DATED AS OF DECEMBER 12, 1997

          This Fourth Amendment and Waiver (this "Amendment"), dated as of April
20, 2001, is made by and among MATERIAL SCIENCES CORPORATION, a Delaware
corporation (the "Company"), the financial institutions party hereto (the
"Banks"), and Bank of America, N.A., as agent for the Banks (in such capacity,
the "Agent"). Unless otherwise defined, terms defined in the Credit Agreement
shall have the same respective meanings when used herein.


                             W I T N E S S E T H:
                             -------------------

          WHEREAS, the Company, the Banks and the Agent are parties to that
certain Credit Agreement, dated as of December 12, 1997 (as amended or modified
and in effect on the date hereof, the "Credit Agreement");

          WHEREAS, the Company has requested that the Banks and the Agent agree
to amend or modify the Credit Agreement as set forth herein; and

          WHEREAS, the Banks and the Agent are willing to amend or modify the
Credit Agreement on the terms and conditions contained herein.

          NOW, THEREFORE, in consideration of the premises, the mutual covenants
herein contained and other good and valuable consideration (the receipt,
adequacy and sufficiency of which is hereby acknowledged), the parties hereto,
intending legally to be bound, hereby agree as follows:

                                   ARTICLE I

                                  AMENDMENTS
                                  ----------

     The Credit Agreement is amended as follows:

          (a)  Article I of the Credit Agreement is hereby amended so as to add
     the following definitions:

          "Bekaert" means Bekaert Corporation, a Delaware corporation (or N.V.
           -------
     Bekaert, S.A., a Belgium corporation, or a subsidiary thereof).

          "ISF" means Innovative Specialty Films, LLC, a Delaware limited
           ---
     liability company comprising the joint venture structured pursuant to the
     ISF Joint Venture Agreement.

          "ISF Closing" means the date the ISF Transaction is consummated.
           -----------

          "ISF Joint Venture Agreement" means the Contribution and Joint Venture
           ---------------------------
     Formation Agreement dated as of October 15, 1998 between MSC/SFI and
     Bekaert.
<PAGE>

          "ISF Letter of Intent" means a Letter of Intent among the Company,
           --------------------
     Bekaert, MSC/SFI and ISF relating to the ISF Transaction (The ISF Letter of
     Intent may be entered into after the date of the Fourth Amendment, it being
     understood that upon execution thereof, the Company shall promptly furnish
     a copy thereof to the Banks.)

          "ISF Transaction Agreement" means the definitive agreement(s)
           -------------------------
     evidencing the ISF Transaction.

          "ISF Net Cash Proceeds" means the cash proceeds received by the
           ---------------------
     Company from the ISF Closing, net of taxes, expenses and other amounts.

          "ISF Transaction" means the transaction pursuant to which the MSC/SFI
           ---------------
     Net Assets shall be combined with ISF or its business, resulting in the ISF
     Net Cash Proceeds.

          "MSC/SFI" means MSC Specialty Films, Inc., a Subsidiary of the
           -------
     Company.

          "MSC/SFI Net Assets" means the assets of MSC/SFI, together with
           ------------------
     related liabilities consisting of third party debt and ordinary course
     payables and accruals, as represented by the financial statements of
     MSC/SFI dated February 28, 2001 (a copy of which the Company warrants have
     been furnished to the Banks).

          (b)  Article I of the Credit Agreement is further amended so that the
     definition of "Adjusted EBITDA" shall read in its entirety as follows:

               "Adjusted EBITDA" means, for any period, the Adjusted Net Income
                ---------------
          for such period, plus
                           ----

               (A) the aggregate amount deducted in determining such Adjusted
          Net Income in respect of (i) interest expense, (ii) income taxes,
          (iii) depreciation, (iv) amortization, (v) losses of Joint Ventures,
          as reflected in the consolidated income statement of the Company for
          such period, and (vi) any extraordinary items of loss under GAAP for
          such period and other non-recurring items of loss for such period,
          less
          ----

               (B) the aggregate amount added in determining such Adjusted Net
          Income in respect of (i) income of Joint Ventures, as reflected in the
          consolidated income statement of the Company for such period, and (ii)
          any extraordinary items of gain under GAAP for such period and other
          non-recurring items of gain for such period.

         Adjusted EBITDA shall be determined so as to include cash dividends and
         other cash distributions received by the Company or its Subsidiaries
         from Joint Ventures during such period.  Interest expense shall
         include, without limitation, the portion of  any obligation under
         capital leases allocable to interest expense in accordance with GAAP,
         and the portion of any debt discount that shall be amortized in such
         period. With respect to any period during which an Acquisition was
         consummated, the Adjusted EBITDA shall be determined as if

                                      -2-
<PAGE>

         such Acquisition had occurred at the beginning of such period. After
         the ISF Closing (if it occurs), Adjusted EBITDA shall exclude 50% of
         the Adjusted EBITDA attributable to the MSC/SFI Net Assets for the
         portion of any such period which occurs before the ISF Closing.

         (c)   Article I of the Credit Agreement is further amended so that the
     definition of "Applicable Margin" shall read in its entirety as follows:

               "Applicable Margin" as to any Offshore Rate Loan, Base Rate
               -----------------
         Loan or Commitment Fee, means a margin per annum based on the
         Consolidated Debt to Adjusted EBITDA Ratio, as follows:

         ======================================================================
          Consolidated Debt to     Margin for                      Margin for
           Adjusted EBITDA       Offshore Rate   Margin for Base   Commitment
              Ratio (R)               Loan          Rate Loan          Fee
         ======================================================================


          3.5:1*R                    3.000%           1.500%          0.500%
         ----------------------------------------------------------------------
          3.0:1*R*3.5:1              2.500%           1.000%          0.375%
         ----------------------------------------------------------------------
          2.50:1*R*3.0:1             2.250%           0.750%          0.375%
         ----------------------------------------------------------------------
          2.00:1*R*2.50:1            2.000%           0.500%          0.250%
         ----------------------------------------------------------------------
          R*2.00:1                   1.750%           0.250%          0.250%
         ======================================================================

          * equals to less than

          For purposes of the foregoing table, "R" means the "Consolidated Debt
          to Adjusted EBITDA Ratio." The Applicable Margin will be adjusted,
          based on the Consolidated Debt to Adjusted EBITDA Ratio as of the last
          day of each fiscal quarter, as reflected in the Compliance Certificate
          furnished pursuant to subsection 7.2(b), such adjustment to occur on
          the first day of the calendar month immediately succeeding the
          calendar month in which the Compliance Certificate is received;
          provided, that if the Company fails to deliver a Compliance
          Certificate by the date required pursuant to subsection 7.2(b), the
          margin in the top row shall apply until such Compliance Certificate is
          delivered. Notwithstanding the foregoing, for the period from April
          20, 2001 to the date the Agent shall have received the Compliance
          Certificate for the quarter ending August 31, 2001, the Applicable
          Margin for Base Rate Loans shall be 1.75% per annum, the Applicable
          Margin for Offshore Rate Loans shall be 3.25% per annum, and the
          Applicable Margin for the Commitment Fee shall be 0.50% per annum.

          (d)   Article I of the Credit Agreement is further amended so that the
     definition of "Combined Commitment" shall read in its entirety as follows:

               "Combined Commitment" means $50,000,000 as such amount may be
                -------------------
          from time to time reduced under Sections 2.5 or 2.7 of this Agreement
          or pursuant to the Fourth Amendment to this Agreement.

                                      -3-
<PAGE>

          (e)  Article I of the Credit Agreement is further amended so that the
     definition of "Commitment" shall read in its entirety as follows:

               "Commitment" means, with respect to (i) The Northern Trust
                ----------
          Company, $13,888,888.88 and (ii) Bank of America, $36,111,111.12, in
          each case as the same may be reduced pursuant to Sections 2.5 or 2.7
          or as a result of one or more assignments under Section 12.8, or
          pursuant to the Fourth Amendment to this Agreement.

          (f)  Article I of the Credit Agreement is further amended so that the
     definition of "Consolidated Debt" shall read as follows:

               "Consolidated Debt" means, at any time, all Indebtedness of the
                -----------------
          Company and its Subsidiaries on a consolidated basis.

          (g)  Article I of the Credit Agreement is further amended by adding
     thereto a definition of "Consolidated Debt to Adjusted EBITDA Ratio" as
     follows:

               "Consolidated Debt to Adjusted EBITDA Ratio" means as of any
                ------------------------------------------
          date of determination, the ratio of (i) total consolidated
          Indebtedness of the Company on such date to (ii) Adjusted EBITDA for
          the most recent period of four consecutive fiscal quarters then ended.

          (h)  Article I of the Credit Agreement is further amended so as to add
     thereto a definition of "Fixed Charge Coverage Ratio", as follows:

               "Fixed Charge Coverage Ratio" means for any period the ratio of:
                ---------------------------

               (A)(i)  Adjusted EBITDA plus consolidated operating lease
          payments of the Company, less consolidated capital expenditures of the
                                   ----
          Company for such period, less consolidated net cash income taxes paid
                                   ----
          in cash during such period, to

               (B)(i) consolidated operating lease payments of the Company
          during such period, plus (ii) consolidated net interest expense
                              ----
          (including rent allocable to interest expense under capital leases and
          amortization of debt discount) of the Company paid in cash during such
          period, plus (iii) principal payments during such period on
          consolidated long-term Indebtedness of the Company (including the
          current portion thereof).

          After the ISF Closing (if it occurs), the Fixed Charge Coverage Ratio
          shall be determined so as to exclude fixed charges attributable to the
          MSC/SFI Net Assets for any portion of such period which occurs before
          the ISF Closing, such fixed charges so attributable to the MSC/SFI Net
          Assets to consist of operating lease payments, capital expenditures,
          net cash income taxes, interest paid by the Company during such period
          on up to $20,000,000 of principal of the Revolving Loans (but only to
          the extent such principal was outstanding, as

                                      -4-
<PAGE>

          calculated by the Company, with the concurrence of the Agent),
          interest expense with respect to Indebtedness (other than the
          Revolving Loans), and principal payments on long-term Indebtedness
          (including the current portion thereof). For any period during which
          an Acquisition shall have been consummated, the Fixed Charge Coverage
          Ratio shall be determined as if such Acquisition were consummated at
          the beginning of such period.

          (i)  Article I of the Credit Agreement is further amended so that the
     definition of "L/C Commitment" shall read in its entirety as follows:

                    "L/C Commitment" means the commitment of the Issuing Bank
                     --------------
          to Issue, and the commitment of the Banks severally to participate in,
          Letters of Credit (including any Time Drafts which have been accepted)
          from time to time Issued or outstanding under Article III, in an
          aggregate amount not to exceed the amount of $10,000,000, as the same
          shall be reduced as a result of a reduction in the L/C Commitment
          pursuant to Section 2.5; provided that the L/C Commitment is a part of
          the Combined Commitment, rather than a separate, independent
          commitment.

          (j)  Section 2.5 of the Credit Agreement is hereby amended so that the
     third sentence shall read in its entirety as follows:

          Any reduction of the Combined Commitment shall be applied to each Bank
          according to its Pro Rata Share.

          (k)  Section 6.11 of the Credit Agreement is hereby amended to read in
     its entirety as follows:

                    6.11  Financial Condition.  (a) The audited consolidated
                          -------------------
          financial statements of the Company and its Subsidiaries dated
          February 28, 2001, and the related consolidated statements of income
          or operations, shareholders' equity and cash flows for the fiscal year
          ended on that date: (i) were prepared in accordance with GAAP
          consistently applied throughout the period covered thereby; and (ii)
          fairly present the financial condition of the Company and its
          Subsidiaries as of the respective dates thereof and results of
          operations for the period covered thereby; and (b) since February 28,
          2001, there has been no Material Adverse Effect.

          (l)  Section 7.1 of the Credit Agreement is hereby amended so as to
     add subsections (d), (e) and (f) as follows:

                    (d) so long as the Consolidated Debt to Adjusted EBITDA
          Ratio exceeds 2.75:1.0, not later than 45 days after the end of each
          month (commencing with the month of April, 2001), a copy of an
          unaudited consolidated and consolidating balance sheet of the Company
          and its Subsidiaries as at the end of such month and the related
          consolidated and consolidating statements of income and cash flows for
          such month, certified by

                                      -5-
<PAGE>

          a Responsible Officer as having been developed and used in connection
          with the preparation of the financial statements referred to in
          subsection 7.1(a);


                 (e) commencing with the fiscal year ended December 31, 2000, as
          soon as available, but not later than 90 days after the end of each
          fiscal year of ISF (or 150 days in the case of its fiscal year ended
          December 31, 2000), a copy of the audited consolidated balance sheet
          of ISF and its Subsidiaries as at the end of such year and the related
          consolidated statements of income or operations, shareholders' equity
          and cash flows for such year, setting forth in each case in
          comparative form the figures for the previous fiscal year, and
          accompanied by the opinion of an Independent Auditor, which report
          shall state that such consolidated financial statements present fairly
          the financial position for the periods indicated in conformity with
          GAAP applied on a basis consistent with prior years. Such opinion
          shall not be qualified or limited because of a restricted or limited
          examination by the Independent Auditor of any material portion of the
          ISF's or any Subsidiary's records; and

                 (f) within 45 days after the end of each of the first three
          fiscal quarters of each fiscal year (commencing with the fiscal
          quarter ended March 31, 2001), a copy of the unaudited consolidated
          balance sheets of ISF and its Subsidiaries, and the related
          consolidated statements of income, shareholders' equity and cash flows
          for such quarter, all certified by a Responsible Officer as having
          been developed and used in connection with the preparation of the
          financial statements referred to in subsection 7.1(e).

          (m) Section 7.2(b) of the Credit Agreement is hereby amended to read
in its entirety as follows:

                 (b) concurrently with the delivery of the financial statements
          referred to in subsections 7.1(a) and (b), a Compliance Certificate
          executed by a Responsible Officer (it being understood that such
          Compliance Certificate shall be revised to reflect the Fourth
          Amendment);

          (n) Section 8.4 of the Credit Agreement is hereby amended by adding
the following at the end of such Section:

                 Notwithstanding the foregoing, on and after April 20, 2001, the
          Company shall not, and shall not permit any Subsidiary to, make any
          Investment pursuant to subsections 8.4(d), (e) or (k), except for the
          following: (i) the ISF Transaction, (ii) Investments in Joint Ventures
          entered into before such date (the "Existing JV's") in an aggregate
          amount not exceeding $3,500,000 for all such Existing JV's, (iii)
          Investments in a Joint Venture in Asia to be entered into after such
          date ("Asian JV") in an aggregate amount not exceeding $500,000 for
          the Asian JV, (iv) an Investment in ISF of up to $3,500,000 to permit
          ISF to acquire NeoVac (the "NeoVac Investment"), and (v) the
          Acquisition of GAC for cash consideration not exceeding $7,000,000;
          provided, however, that after the ISF Closing, the Investments of the
          --------- -------
          Company

                                      -6-
<PAGE>

          and its Subsidiaries made after April 20, 2001 in Joint Ventures
          (whether the Existing JV's, or the Asian JV, or the Joint Venture
          resulting from the ISF Transaction) may be increased up to (but not in
          excess of) $8,000,000 for all such Joint Ventures (in addition to the
          NeoVac Investment).

          (o) Section 8.5 of the Credit Agreement is hereby amended by adding
the following at the end of such Section:

                 Notwithstanding the foregoing, on and after April 20, 2001, the
          Company shall not, and shall not permit any Subsidiary to, incur any
          Indebtedness pursuant to subsections 8.5(d), (e) and (f), except for
          Indebtedness of up to $500,000 in connection with capital leases
          entered into after such date.

          (p) Section 8.9 of the Credit Agreement is hereby amended by adding
the following at the end of such Section:

                 Notwithstanding the foregoing, on and after April 20, 2001, the
          Company shall not, and shall not permit any Subsidiary to, enter into
          any Joint Venture (other than the ISF Transaction and the Asian JV).

          (q) Section 8.10(b) of the Credit Agreement is amended by substituting
"$7,000,000" for "$10,000,000".

          (r) Section 8.11 of the Credit Agreement is hereby amended to read in
its entirety as follows:

                 8.11 Restricted Payments. After April 20, 2001, the Company
                      -------------------
          shall not declare or make any dividend payment or other distribution
          of assets, properties, cash, rights, obligations or securities on
          account of any shares of any class of its capital stock, or purchase,
          redeem or otherwise acquire for value any shares of its capital stock
          or any warrants, rights or options to acquire such shares, now or
          hereafter outstanding, except that the Company may declare and make
          dividend payments or other distributions payable solely in its common
          stock.

          (s) Article VIII of the Credit Agreement is hereby amended by adding
thereto Section 8.16 as follows:

                 8.16  ISF.  Notwithstanding any provisions herein to the
                       ---
          contrary, the Company shall not incur or permit any Subsidiary to
          incur any Guaranty Obligation with respect to any Indebtedness of ISF.

          (t) Article VIII of the Credit Agreement is amended by adding thereto
Section 8.17 as follows:

                                      -7-
<PAGE>

                 8.17 Minimum Cash Balance.  After the ISF Closing until
                      --------------------
          compliance by the Company with the financial tests in Sections 9.1,
          9.2 and 9.3 hereof for the fiscal quarter ending February 28, 2002 (as
          evidenced by a Compliance Certificate received by the Agent for such
          quarter), the Company shall not at any time permit the balance of
          readily available cash on deposit with one or more of the Banks, to be
          less than $10,000,000.

          (u) Section 9.1 of the Credit Agreement is hereby amended to read in
its entirety as follows:

                 9.1  Minimum Net Worth. The Company shall not permit at any
                      -----------------
          time the consolidated net worth of the Company and its Subsidiaries to
          be less than the sum of (i) $145,000,000 plus (ii) 40% of cumulative
          consolidated net earnings (but without giving effect to any
          consolidated net losses) of the Company and its Subsidiaries accruing
          after February 28, 2001.

          (v) Section 9.2 of the Credit Agreement is hereby amended to read in
its entirety as follows:

                 9.2  Consolidated Debt to Adjusted EBITDA Ratio. The Company
                      ------------------------------------------
          shall not permit, as of the last day of any period consisting of four
          consecutive fiscal quarters, its Consolidated Debt to Adjusted EBITDA
          Ratio to be greater than the ratio applicable to such period, as
          follows:


          ======================================================================
                         Ratio                  Period Ending
          ---------------=====------------------============--------------------
                         4.25:1                 May 31, 2001
          ----------------------------------------------------------------------
                         4.00:1                 August 31, 2001
          ----------------------------------------------------------------------
                         3.25:1                 November 30, 2001
          ----------------------------------------------------------------------
                         2.75:1                 February 28, 2002 and thereafter
          ======================================================================

          (w) Section 9.3 of the Credit Agreement is hereby amended to read in
its entirety as follows:

                 9.3 Fixed Charge Coverage Ratio. The Company shall not permit,
                     ---------------------------
          as of the last day of any period consisting of four consecutive fiscal
          quarters, its Fixed Charge Coverage Ratio to be less than the ratio
          applicable to such period, as follows:

                                      -8-
<PAGE>

          ======================================================================
                        Ratio                               Period Ending
          --------------=====-------------------------------=============-------
                        0.95:1                  May 31, 2001
          ----------------------------------------------------------------------
                        1.05:1                  August 31, 2001
          ----------------------------------------------------------------------
                        1.25:1                  November 30, 2001
          ----------------------------------------------------------------------
                        1.50:1                  February 28, 2002 and thereafter
          ======================================================================

          (x) Section 10.1 of the Credit Agreement is hereby amended by adding
subsection (m) as follows:

                 (m) ISF. At any time after the ISF Closing, (i) the Company's
                     ---
          equity or voting interest in ISF shall be less than 50% (subject to
          casting votes reasonably acceptable to the Agent), or ISF shall have
          any Indebtedness other than up to $10,000,000 of revolving
          Indebtedness to Bekaert.

          (y) The Credit Agreement (together with each of the related exhibits,
schedules and other Loan Documents) is further amended by substituting "Bank of
America, N.A." for "Bank of America National Trust and Savings Association"
wherever such words appear, and by substituting "Bank of America" for "BofA"
wherever such term appears.

          (z) The Credit Agreement is further amended by deleting "$115,000,000"
opposite the name of Bank of America on the signature pages thereof and by
deleting "$25,000,000" opposite the name of The Northern Trust Company on the
signature pages thereof.

                                  ARTICLE II

                               WAIVER AND CONSENT
                               ------------------



          (a) Waiver. The Banks hereby waive any Default or Event of Default
              ------
     arising from noncompliance by the Company as of February 28, 2001 with the
     provisions of Section 9.2 (Debt to Cash Flow Ratio) and 9.3 (Fixed Charge
     Coverage Ratio) of the Credit Agreement (as in effect before giving effect
     to this Amendment); it being understood that the foregoing waiver is
     specific in time and in intent and does not constitute, nor shall it be
     construed as, a waiver of any other right, power or privilege under the
     Credit Agreement, or under any agreement, contract, indenture, document or
     other instrument mentioned in the Credit Agreement; nor does the foregoing
     waiver preclude other or further exercise of any other right, power or
     privilege, nor shall the waiver of any right, power, privilege or default
     hereunder, or under any agreement, contract, indenture, document, or
     instrument mentioned in the Credit Agreement, constitute a waiver of any
     other default of any other term or provision.

          (b) Consent. Notwithstanding the provisions of Article VIII of the
              -------
     Credit Agreement, the Banks hereby consent to the ISF Transaction,
     provided, however that
     --------  -------

                                      -9-
<PAGE>

     (i) prior to the ISF Closing, the Company shall have furnished to the Banks
     a certified copy of the ISF Transaction Agreement and related documents,
     (ii) the ISF Closing is on or before June 1, 2001, (iii) concurrent with
     the ISF Closing, the Company shall receive ISF Net Cash Proceeds in
     immediately available funds of not less than $35,000,000, (iv) the Company
     shall immediately apply all of such ISF Net Cash Proceeds to the payment of
     the Revolving Loans, (v) concurrent with the ISF Closing, the Combined
     Commitment shall automatically reduce to $20,000,000 (such reduction to be
     pro rata among the Banks according to their respective Commitments), (vi)
     after giving effect to the ISF Closing, the Company's equity and voting
     interest in ISF shall not be less than 50% (subject to casting votes
     reasonably acceptable to the Agent), and (vi) after giving effect to the
     ISF Closing, ISF shall have no Indebtedness except as permitted in Section
     10.1(m) of the Credit Agreement as herein amended.

          (c) Release. The Banks further agree that to the extent that the stock
              -------
     of MSC/SFI and/or Solar-Guard International, Inc., is transferred as part
     of the ISF Transaction, the Guaranties of such Persons pursuant to the
     Credit Agreement shall be deemed to have been released.

                                  ARTICLE III

                         REPRESENTATION AND WARRANTIES
                         -----------------------------

     The Company hereby represents and warrants to the Banks and the Agent that:

          (a) Authorization, etc. The execution, delivery and performance of
              -------------------
     this Amendment are within the Company's corporate authority, have been duly
     authorized by all necessary corporate action, have received all necessary
     consents and approvals (if any shall be required), and do not and will not
     contravene or conflict with any provision of law or of the Certificate of
     Incorporation or By-laws of the Company or its Subsidiaries, or of any
     other agreement binding upon the Company or its Subsidiaries or their
     respective property.

          (b) Validity. This Amendment constitutes the legal, valid, and binding
              --------
     obligations of the Company, enforceable against the Company in accordance
     with its terms, except as enforceability may be limited by applicable
     bankruptcy, insolvency, or similar laws affecting the enforcement of
     creditors' rights generally or by equitable principles relating to
     enforceability.

          (c) No Default. Except for any Default or Event of Default which will
              ----------
      be cured by this Amendment becoming effective, no Event of Default has
      occurred and is continuing or will result from this Amendment.

          (d) ISF Transaction. (i) The Company has furnished to the Banks a true
              ---------------
     and correct copy of the ISF Joint Venture Agreement and financial
     statements representing the MSC/SFI Net Assets, and (ii) if the ISF Closing
     occurs, the ISF Net Cash Proceeds shall not be less than $35,000,000.

                                      -10-
<PAGE>

                                  ARTICLE IV

                             CONDITIONS PRECEDENT
                             --------------------

     This Amendment shall become effective as of April 20, 2001 (the "Effective
Date"), subject, however, to the receipt by the Agent of the following in form
and substance satisfactory to the Agent:

     (a)  counterparts of this Amendment (or an executed facsimile copy hereof),
executed by the Company and the Banks;

     (b)  evidence of the payment to the Agent in immediately available funds of
(i) an amendment fee for the account of each Bank equal to 25 basis points times
such Bank's Commitment (based on a Combined Commitment of $50,000,000), (ii) an
arrangement fee for the account of the Agent equal to the arrangement fee set
forth in a fee letter between the Company and the Agent, and (iii) all legal
fees and expenses of the Agent to the extent theretofore invoiced;

     (c)  a certificate of the Secretary or the Assistant Secretary of the
Company as to resolutions, and the signatures and incumbency of officers
authorized to sign this Amendment;

     (d)  an opinion of Kirkland & Ellis, counsel to the Company, as to the due
authorization execution and delivery by the Company of this Amendment; and

     (e)  a certified copy of the ISF Joint Venture Agreement and the financial
statements representing the MSC/SFI Net Assets.

                                   ARTICLE V

                                 MISCELLANEOUS
                                 -------------

     (a)  Restatement (including SwingLine Facility). Promptly following the
          -----------------------------------------
effectiveness of this Amendment, the parties agree to amend and restate the
Credit Agreement so as to (i) provide for a $5 million swingline facility by
Bank of America (it being understood that such swingline facility shall be a
part of the Combined Commitment rather than a separate, independent commitment),
(ii) update schedules, and (iii) reflect the Credit Agreement as amended hereby.

     (b)  Documents Remain in Effect. Except as amended or modified by this
          --------------------------
Amendment, the Credit Agreement remains in full force and effect and the Company
confirms that its representations, warranties, agreements and covenants
contained in, and obligations and liabilities under, the Credit Agreement and
each of the other Loan Documents are true and correct in all material respects
as if made on the date hereof, except where such representation, warranty,
agreement or covenant speaks as of a specified date. References to the Credit
Agreement in any other document shall be deemed to include a reference to the
Credit Agreement as amended or modified hereby, whether or not reference is made
to this Amendment.

                                      -11-
<PAGE>

     (c)  Expenses. The Company covenants to pay to or reimburse the Agent, upon
          --------
demand, for all reasonable costs and expenses (including legal expenses) in
connection with the development, preparation, negotiation, execution and
delivery of this Amendment and the Loan Documents.

     (d)  Headings. Section headings used in this Amendment are for convenience
          --------
of reference only, and shall not affect the construction of this Amendment.

     (e)  Governing Law. This Amendment shall be a contract made under and
          -------------
governed by the internal laws of the State of Illinois, without giving effect to
principles of conflicts of laws.

     (f)  Cumulative Rights. All obligations of the Company and rights of the
          -----------------
Banks and the Agent, that are expressed herein, shall be in addition to and not
in limitation of those provided by applicable law.

     (g)  Severability. Whenever possible, each provision of this Amendment
          ------------
shall be interpreted in such manner as to be effective and valid under
applicable law; but if any provision of this Amendment shall be prohibited by or
invalid under applicable law, such provision shall be ineffective to the extent
of such prohibition or invalidity, without invalidating the remainder of such
provision or the remaining provisions of this Amendment.

     (h)  No Forbearance. The Company acknowledges and agrees that the execution
          --------------
and delivery by the Agent and the Banks of this Amendment shall not be deemed
(i) to create a course of dealing or otherwise obligate the Agent or the Banks
to forbear or execute similar amendments under the same or similar circumstances
in the future, or (ii) to amend, relinquish or impair any right of the Agent or
the Banks to receive any indemnity or similar payment from any Person or entity
as a result of any matter arising from or relating to this Amendment.

     (i)  Successors and Assigns. This Amendment shall be binding upon and inure
          ----------------------
to the benefit of the parties and thereto and their respective successors and
assigns. No third party beneficiaries are intended in connection with this
Amendment.

     (j)  Counterparts. This Amendment may be executed in any number of
          ------------
counterparts, each of which shall be deemed an original, but all such
counterparts together shall constitute but one and the same instrument. Each of
the parties hereto understands and agrees that this document (and any other
document required herein) may be delivered by any party thereto either in the
form of an executed original or an executed original sent by facsimile
transmission to be followed promptly by mailing of a hard copy original, and
that receipt by the Agent of a facsimile transmitted document purportedly
bearing the signature of a Bank or the Company shall bind such Bank or the
Company, respectively, with the same force and effect as the delivery of a hard
copy original. Any failure by the Agent to receive the hard copy executed
original of such document shall not diminish the binding effect of receipt of
the facsimile transmitted executed original of such document of the party whose
hard copy page was not received by the Agent.

     (k)  Entire Agreement.  This Amendment, together with the Credit Agreement,
          ----------------
contains the entire and exclusive agreement of the parties hereto with reference
to the matters

                                      -12-
<PAGE>

discussed herein and therein. This Amendment supercedes all prior drafts and
communications with respect thereto. This Amendment may not be amended except in
accordance with the provisions of Section 12.1 of the Credit Agreement.

                                 *     *     *

                                      -13-
<PAGE>

          IN WITNESS WHEREOF, the parties hereto have caused the execution and
delivery hereof by their respective representatives thereunto duly authorized as
of the date first herein appearing.

                                        MATERIAL SCIENCES CORPORATION


                                        By:   /s/ James J. Waclawik, Sr.
                                              ----------------------------------
                                        Name:     James J. Waclawik, Sr.
                                              ----------------------------------
                                        Title:    CFO
                                              ----------------------------------


                                        BANK OF AMERICA, as Agent


                                        By:   /s/ Kristine D. Hyde
                                              ----------------------------------
                                        Name:     Kristine D. Hyde
                                              ----------------------------------
                                        Title:    Vice President
                                              ----------------------------------


                                        BANK OF AMERICA, N.A., in its individual
                                        corporate capacity


                                        By:   /s/ Chris D. Buckner
                                              ----------------------------------
                                        Name:     Chris D. Buckner
                                              ----------------------------------
                                        Title:    Vice President
                                              ----------------------------------


                                        THE NORTHERN TRUST COMPANY


                                        By:   /s/ Fredric McClendon
                                              ----------------------------------
                                        Name:     Fredric McClendon
                                              ----------------------------------
                                        Title:    Vice President
                                              ----------------------------------

                                      -14-
<PAGE>

                           GUARANTOR ACKNOWLEDGMENT
                           ------------------------


     The undersigned, each a guarantor or third party pledgor with respect to
the Company's obligations to the Agent and the Banks under the Credit Agreement,
each hereby (i) acknowledge and consent to the execution, delivery and
performance by the Company of the foregoing Fourth Amendment to the Credit
Agreement ("Amendment"), and (ii) reaffirm and agree that the respective
            ---------
guaranty, third party pledge or security agreement to which the undersigned is
party and all other documents and agreements executed and delivered by the
undersigned to the Agent and the Banks in connection with the Credit Agreement
are in full force and effect, without defense, offset or counterclaim.
(Capitalized terms used herein have the meanings specified in the Amendment.)

                                         GUARANTORS
                                         ----------

                                         MSC Pre Finish Metals Inc.
                                         MSC Pre Finish Metals (EGV) Inc.
                                         MSC Pre Finish Metals (MV) Inc.
                                         MSC Pre Finish Metals (MT) Inc.
                                         MSC Laminates and Composites Inc.
                                         MSC Laminates and Composites (EGV) Inc.
                                         MSC Walbridge Coatings Inc.
                                         MSC Specialty Films, Inc.
                                         MSC Pinole Point Steel Inc.
                                         Solar-Gard International, Inc.
                                         MSC Pre Finish Metals (PP) Inc.


Dated: April 20, 2001                    By:    /s/ James J. Waclawik, Sr.
                                                --------------------------------
                                         Title:     CFO
                                                --------------------------------
                                      -15-