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                                                                     EXHIBIT 4.2




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                                 GLASSTECH, INC.

                                       and

               UNITED STATES TRUST COMPANY OF NEW YORK, as Trustee

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                          FIRST SUPPLEMENTAL INDENTURE

                            Dated as of July 2, 1997

                                       to

                                    INDENTURE

                            Dated as of July 2, 1997

                                 by and between

                          GLASSTECH SUB CO., as Issuer

                                       and

               UNITED STATES TRUST COMPANY OF NEW YORK, as Trustee

                            ------------------------


                                  $70,000,000

                          12 3/4% Senior Notes Due 2004

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                                TABLE OF CONTENTS
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                                                                         Page
                                                                         ----

                                    ARTICLE I

                 ASSUMPTION OF OBLIGATIONS OF GLASSTECH SUB CO.

Section 1.01.  Assumption .................................................2

                                   ARTICLE II

                            MISCELLANEOUS PROVISIONS

Section 2.01.  Terms Defined ..............................................2
Section 2.02.  Indenture ..................................................2  
Section 2.03.  Governing Law ..............................................2  
Section 2.04.  Successors .................................................3  
Section 2.05.  Multiple Counterparts ......................................3  
Section 2.06.  Effectiveness ..............................................3  
Section 2.07.  Trustee Disclaimer .........................................3  
                                                                           

SIGNATURES.................................................................4






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         FIRST SUPPLEMENTAL INDENTURE dated as of July 2, 1997, by and between
GLASSTECH, INC., a Delaware corporation ("GLASSTECH"), and UNITED STATES TRUST
COMPANY OF NEW YORK (the "TRUSTEE").

         WHEREAS, GLASSTECH SUB CO., a Delaware corporation (the "COMPANY"),
heretofore executed and delivered to the Trustee an Indenture dated as of July
2, 1997 (the "INDENTURE"), providing for the issuance of $70,000,000 aggregate
principal amount of the Company's 12 3/4% Senior Notes Due 2004 (the "NOTES");
and

         WHEREAS, there have been issued and are now outstanding under the
Indenture, Notes in the aggregate principal amount of $70,000,000; and

         WHEREAS, in connection with the merger of the Company with and into
Glasstech pursuant to an Agreement and Plan of Merger dated as of June 5, 1997,
the Company has been merged with and into Glasstech and in connection therewith,
Glasstech has assumed, by operation of law, all of the Company's debts,
liabilities, duties and obligations, including the Company's obligations in
respect of the Notes and under the Indenture; and

         WHEREAS, Glasstech desires by this First Supplemental Indenture, to
expressly assume the covenants, agreements and undertakings of the Company in
the Indenture and under the Notes; and

         WHEREAS, the execution and delivery of this First Supplemental
Indenture has been authorized by a resolution of the Board of Directors of
Glasstech; and

         WHEREAS, all conditions and requirements necessary to make this First
Supplemental Indenture a valid, binding and legal instrument in accordance with
its terms have been performed and fulfilled by the parties hereto and the
execution and delivery thereof have been in all respects duly authorized by the
parties hereto.

         NOW, THEREFORE, in consideration of the above premises, each party
agrees, for the benefit of the other and for the equal and ratable benefit of
the Holders of the Notes, as follows:
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                                    ARTICLE I

                 ASSUMPTION OF OBLIGATIONS OF GLASSTECH SUB CO.

         Section 1.01. ASSUMPTION. Glasstech hereby expressly and
unconditionally assumes each and every covenant, agreement and undertaking of
the Company in the Indenture as if Glasstech had been the original issuer of the
Notes, and also hereby expressly and unconditionally assumes each and every
covenant, agreement and undertaking in each Note outstanding on the date of this
First Supplemental Indenture and any Notes delivered hereafter. Any Notes
delivered after the date of this First Supplemental Indenture, including Notes
delivered in substitution or exchange for any outstanding Notes, as provided in
the Indenture, may be executed and delivered by Glasstech in its own name, with
such notations, legends or endorsements required by law, stock exchange rules or
usage, and each such Note shall constitute the obligation of Glasstech.

                                   ARTICLE II

                            MISCELLANEOUS PROVISIONS

         Section 2.01. TERMS DEFINED. For all purposes of this First
Supplemental Indenture, except as otherwise defined or unless the context
otherwise requires, terms used in capitalized form in this First Supplemental
Indenture and defined in the Indenture have the meanings specified in the
Indenture.

         Section 2.02. INDENTURE. Except as amended hereby, the Indenture and
the Notes are in all respects ratified and confirmed and all the terms shall
remain in full force and effect.

         Section 2.03. GOVERNING LAW. THIS FIRST SUPPLEMENTAL INDENTURE SHALL
BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW
YORK, AS APPLIED TO CONTRACTS MADE AND PERFORMED WITHIN THE STATE OF NEW YORK,
WITHOUT REGARD TO PRINCIPLES OF CONFLICT OF LAWS. Each of the parties hereto
agrees to submit to the jurisdiction of the courts of the State of New York in
any action or proceeding arising out of or relating to this First Supplemental
Indenture, provided that such jurisdiction shall be non-exclusive.


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         Section 2.04. SUCCESSORS. All agreements of Glasstech in this First
Supplemental Indenture and the Notes shall bind its successors. All agreements
of the Trustee in this Indenture shall bind its successor.

         Section 2.05. MULTIPLE COUNTERPARTS. The parties may sign multiple
counterparts of this First Supplemental Indenture. Each signed counterpart shall
be deemed an original, but all of them together represent the same agreement.

         Section 2.06. EFFECTIVENESS. The provisions of this First Supplemental
Indenture will take effect immediately upon its execution and delivery by the
Trustee in accordance with the provisions of Section 8.06 of the Indenture.

         Section 2.07. TRUSTEE DISCLAIMER. The Trustee accepts the amendment of
the Indenture effected by his First Supplemental Indenture and agrees to execute
the trust created by the Indenture and agrees to execute the trust created by
the Indenture as hereby amended, but only upon the terms and conditions set
forth in the Indenture, including the terms and provisions defining and limiting
the liabilities and responsibilities of the Trustee, which terms and provisions
shall in like manner define and limit its liabilities and responsibilities in
the performance of the trust created by the Indenture as hereby amended, and
without limiting the generality of the foregoing, the Trustee shall not be
responsible in any manner whatsoever for or with respect to any of the recitals
or statements contained herein, all of which recitals or statements are made
solely by Glasstech, or for or with respect to (i) the validity or sufficiency
of this First Supplemental Indenture or any of the terms or provisions hereof,
(ii) the proper authorization hereof by Glasstech by corporate action or
otherwise, (iii) the due execution hereof by Glasstech, (iv) the consequences
(direct or indirect and whether deliberate or inadvertent) of any amendment
herein provided for, and the Trustee makes no representation with respect to any
such matters.


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                                   SIGNATURES

         IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed as of the date first written above.

                                              GLASSTECH, INC.

                                              By: /s/ Mark D. Christman
                                                 ------------------------------
                                                 Name: Mark D. Christman
                                                 Title: President

Attest: /s/ Kenneth H. Wetmore
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                                              UNITED STATES TRUST COMPANY OF 
                                                    NEW YORK, as Trustee

                                              By: /s/ Cynthia Chaney
                                                 -------------------------------
                                                 Name: Cynthia Chaney
                                                 Title: Assistant Vice President