<PAGE>

                                                                   EXHIBIT 10.1

             INCREASE IN COMMITMENTS AND LENDER ADDITION AGREEMENT

         This INCREASE IN COMMITMENTS AND LENDER ADDITION AGREEMENT (this
"Agreement") is dated as of the 24th day of September, 2002 (the "Effective
Date") by and among P. H. Glatfelter Company, a Pennsylvania corporation
("Company"), PHG Tea Leaves, a Delaware corporation ("PHG Tea Leaves"),
Papierfabrik Schoeller & Hoesch GmbH & Co. KG, a limited partnership organized
under the laws of the Federal Republic of Germany ("Papierfabrik Schoeller &
Hoesch"), S & H Verwaltungsgesellschaft mbH, a company with limited liability
organized under the laws of the Federal Republic of Germany ("S&H mbH" together
with Company, PHG Tea Leaves and Papierfabrik Schoeller & Hoesch, the
"Borrowers"), Deutsche Bank AG New York Branch, as administrative agent
("Agent"), and SunTrust Bank ("New Lender"). Except as otherwise defined
herein, terms used herein and defined in the Credit Agreement (as defined
below) shall be used herein as therein defined.

                             W I T N E S S E T H :

         WHEREAS, the Borrowers, the Lenders and Agent have entered into a
Credit Agreement, dated as of June 24, 2002 (as amended, restated, supplemented
or otherwise modified from time to time, the "Credit Agreement"), providing for
the making of Loans to the Borrowers and the issuance of, and participation in,
Letters of Credit for the account of Company, all as contemplated therein;

         WHEREAS, Section 4.1(c) of the Credit Agreement provides that the
Total Revolving Commitment may be increased by $22,500,000 (the "Increase
Amount") in accordance with the provisions of Section 4.1(c) and pursuant to
the procedures set forth therein;

         WHEREAS, Company has provided written notice to Agent of its desire to
increase the Total Revolving Commitment by the Increase Amount and the
procedures set forth in Section 4.1(c) have been undertaken;

         WHEREAS, New Lender has agreed to provide a Revolving Commitment equal
to the Increase Amount and to become a Lender pursuant to the terms of the
Credit Agreement;

         NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants and agreements set forth herein, and other good and valuable
consideration the receipt and adequacy of which are hereby acknowledged, the
parties hereto agree as follows:

         1.       New Lender hereby agrees in accordance with Section 4.1(c) of
the Credit Agreement to provide a Revolving Commitment in the amount of the
Increase Amount. New Lender (i) confirms that it has received a copy of the
Credit Agreement and the other Loan Documents, together with copies of the
financial statements referred to therein and such other documents and
information as it has deemed appropriate to make its own credit analysis and
decision to enter into this Agreement; (ii) agrees that it will, independently
and without reliance upon Agent or any other Lender and based on such documents
and information as it shall deem appropriate at the time, continue to make its
own credit decisions in taking or not taking action under the Credit Agreement;
(iii) confirms that it is an Eligible Assignee under Section 12.8(c) of the
Credit Agreement; (iv) appoints and authorizes the Agent to take such action as
agent on its behalf and to exercise such powers under the Credit Agreement and
the other Loan Documents as are delegated to Agent by the terms thereof,
together with such powers as are reasonably incidental thereto; and (v) agrees
that it will perform in accordance with their terms all of the obligations
which by the terms of the Credit Agreement are required to be performed by it
as a Lender. On the Effective Date, New Lender (i) accepts and shall provide
its Revolving Commitment in the amount of the Increase Amount, (ii) agrees to
and shall become a party to the Credit Agreement and shall be bound by and have
the rights and obligations of a Lender thereunder and under the other Loan
Documents and (iii) agrees to make available the amount of its Pro Rata Share
of the Borrowing occurring on or about the Effective Date.
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         2.       As of the Effective Date, Schedule 1.1(a) to the Credit
Agreement shall be amended and restated to read as set forth on Schedule 1.1(a)
hereto and the Total Revolving Commitment shall be increased by the Increase
Amount to $125,000,000.

         3.       The invalidity, illegality or unenforceability in any
jurisdiction of any provision or obligation under this Agreement shall not
affect or impair the validity, legality or enforceability of the remaining
provisions or obligations under this Agreement or of such provision or
obligation in any other jurisdiction.

         4.       THIS AGREEMENT WILL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, INCLUDING SECTIONS 5-1401
AND 5-1402 OF THE NEW YORK GENERAL OBLIGATIONS LAW BUT EXCLUDING ALL OTHER
CHOICE OF LAW AND CONFLICTS OF LAWS RULES.

         5.       This Agreement and any amendments, waivers, consents or
supplements may be executed in any number of counterparts and by different
parties hereto in separate counterparts, each of which when so executed and
delivered shall be deemed an original, but all of which counterparts together
shall constitute but one and the same instrument. This Agreement shall be
effective as of the Effective Date.

         6.       This Agreement, including all exhibits and other documents
attached hereto or incorporated by reference herein, constitutes the entire
agreement of the parties with respect to the subject matter hereof and
supersedes all other understandings, oral or written, with respect to the
subject matter hereof.
<PAGE>
                                SCHEDULE 1.1(a)

                                  COMMITMENTS

<TABLE>
<CAPTION>
                                                           Amount of
Lenders                                               Revolving Commitment
-------                                               --------------------
<S>                                                   <C>
Deutsche Bank AG New York Branch                          $ 37,500,000
Allfirst Bank                                             $ 32,500,000
PNC Bank, National Association                            $ 32,500,000
SunTrust Bank                                             $ 22,500,000
                                                          ------------
      Total                                               $125,000,000
</TABLE>