Exhibit 10
                              PPG INDUSTRIES, INC.
                          DIRECTORS' COMMON STOCK PLAN
                          ----------------------------


1.   PURPOSE.  The purpose of this Plan is to align the financial interests of
     -------                                                                  
     the Company's shareholders with those of its Non-Employee Directors by
     providing such Directors with compensation in the form of Company Common
     Stock.

2.   DEFINITIONS.
     ----------- 

     "Account" means the account maintained for each Non-Employee Director to
     which Common Stock Equivalents and Dividend Equivalents are credited.

     "Annual Contribution" means the Common Stock Equivalents credited to an
     Account each year under Section 4.1.

     "Board" means the Board of Directors of the Company.

     "Change in Control" has the same meaning as given to that term in the PPG
     Industries, Inc. Deferred Compensation Plan for Directors, as such plan may
     be amended from time to time.

     "Committee" means the Officers-Directors Compensation Committee of the
     Board.

     "Common Stock" means the common stock, par value $1.66 2/3 per share, of
     the Company.

     "Common Stock Equivalent" means a hypothetical share of Common Stock.

     "Company" means PPG Industries, Inc.

     "Dividend Equivalent" means an additional number of Common Stock
     Equivalents the Company shall credit to each Account as of each dividend
     payment date declared with respect to the Company's Common Stock.  The
     additional number of Common Stock Equivalents to be credited to each
     Account shall be equal to:

 
          (a)  the product of (i) the dividend per share of the Common Stock
               which is payable as of the dividend payment date, multiplied by
               (ii) the number of whole Common Stock Equivalents credited to the
               Account as of the applicable dividend record date;

                                     DIVIDED BY
                                     ----------

          (b)  the closing price of a share of the Common Stock on the dividend
               payment date (or if such stock was not traded on that date, on
               the next preceding date on which it was traded), as reported in
               the New York Stock Exchange Composite Transactions.

     "Eligible Spouse" means the spouse who is legally married to a Participant
     at the time of his or her death.

     "Non-Employee Director" means a director of the Company who is not a
     present or former employee of the Company or any of its subsidiaries.

     "Participant" means a Non-Employee Director who has become eligible to
     receive benefits under this Plan.  A Non-Employee Director becomes a
     Participant when he or she (1) resigns from the Board and (2) attains 70
     years of age; provided however, that the Committee may waive the
     requirement that the Participant attain 70 years of age.

     "Plan" means the PPG Industries, Inc. Directors' Common Stock Plan.

     "Retainer" means the base annual retainer fee paid to each Non-Employee
     Director by the Company.  It does not include committee retainer fees,
     meeting attendance fees, committee chairperson's retainer fees or any other
     compensation other than the base annual retainer fee.

     "Service" means the period of time a Non-Employee Director serves on the
     Board.

3.   EFFECTIVE DATE.  This Plan shall be effective on and after January 1, 1988.
     --------------                                                             

                                       2

 
4.   CREDITING ACCOUNTS.
     ------------------ 

4.1  Each year on the day following the Annual Meeting of Shareholders of the
     Company, the Company shall credit the Account of each Non-Employee Director
     who serves on the Board on that day with the number of Common Stock
     Equivalents determined by dividing one-half of such Director's Retainer by
     the average closing price of the Common Stock in the New York Stock
     Exchange Composite Transactions during the 5 days for which such price is
     available immediately preceding such day of crediting.  The Account of any
     person who ceases to be a Director prior to April 16, 1999, shall be
     credited with no more than 10 such Annual Contributions and the total
     number of such Annual Contributions made to his or her Account under this
     Section 4.1 plus the number which is multiplied by $10,000 to determine the
     amount credited to the Account under Section 4.2 will not exceed 10.  Any
     Non-Employee Director who is a Director of the Company on or after April
     16, 1999 and whose total number of Annual Contributions was limited to 10
     under the Plan in effect prior to April 16, 1999, shall have credited to
     his or her Account such additional Annual Contributions and Dividend
     Equivalents as are necessary so that such Account is credited with the
     number of Common Stock Equivalents it would have had credited if such
     limitation had never existed.

4.2  On the day following the 1988 Annual Meeting of Shareholders of the
     Company, the Company shall credit the Account of each Non-Employee Director
     who is age 61 or older on that date with the number of Common Stock
     Equivalents determined by (1) multiplying $10,000 times his or her number
     of full fiscal years of Service, but such number of full fiscal years of
     Service shall not exceed the number determined by subtracting 60 from the
     Non-Employee Director's age on the day immediately following the 1988
     Annual Meeting of Shareholders and (2) then dividing that amount by the
     average closing price of the Common Stock in the New York Stock Exchange
     Composite Transactions during the 5 days for which such price is available
     immediately preceding such day.

                                       3

 
5.   PAYMENTS OF BENEFITS.
     -------------------- 

5.1  Only Participants or Eligible Spouses will receive benefits under this
     Plan.  Except as set forth in Section 5.4, the Account of a Non-Employee
     Director will be forfeited if he or she does not become a Participant.

5.2  Benefits will be paid in the form of Common Stock (and cash for any
     remaining partial shares of Common Stock as described below) in annual
     installments each year on May 1 (or on the next business day if May 1 is
     not a business day) commencing the first May 1 the Participant is eligible
     to receive benefits; provided, however, that the first payment to a
     Participant shall not be made until 6 months and 10 days after the
     Participant ceases to be a Non-Employee Director.  The number of annual
     installments paid to each Participant shall be equal to his or her number
     of full fiscal years of Service, but shall not exceed 10 annual
     installments.  The number of shares of Common Stock attributable to each
     installment shall be equal to the whole number obtained by dividing the
     number of Common Stock Equivalents then credited to the Participant's
     Account by the number of unpaid installments.  Common Stock Equivalents
     with respect to which payment has not yet occurred shall continue to be
     credited with Dividend Equivalents.  As of the date on which the last
     payment of benefits is made to any Participant, the Company shall pay the
     Participant, in cash, the value of any remaining fractional Common Stock
     Equivalent based on the closing sale price of the Common Stock on the New
     York Stock Exchange Composite Transactions on the last date for which such
     price is available prior to the payment date.  Notwithstanding the
     foregoing, payments from the account of any Participant who ceased to be
     director of the Company before August 15, 1996 shall continue to be paid in
     the manner provided by the Plan as effective on August 15, 1996.

5.3  If a Non-Employee Director dies prior to resigning, or after resigning from
     the Board but before becoming eligible to receive benefits hereunder, he or
     she shall be deemed to have become a Participant eligible to receive
     benefits hereunder immediately prior to his or her death, and such benefits
     shall be paid to the Participant's Eligible Spouse.  If a Participant dies
     after becoming eligible to receive benefits hereunder, but prior to
     receiving all the benefits due him or her hereunder, such remaining
     benefits shall

                                       4

 
     be paid to the Participant's Eligible Spouse. Unpaid benefits under this
     Plan will be forfeited in the event the Participant's death and
     Participant's Eligible Spouse's death occur prior to the total amount of
     benefits due hereunder having been paid.

6.   CHANGES IN STOCK.  In the event of any change in the outstanding shares of
     ----------------                                                          
     the Common Stock, or in the number thereof, by reason of any stock dividend
     or split, recapitalization, merger, consolidation, exchange of shares or
     other similar change, a corresponding change will be made in the number of
     Common Stock Equivalents and Dividend Equivalents, if any, credited to each
     Account, unless the Committee determines otherwise.

7.   ACCELERATION.  The Committee, in its sole discretion, may accelerate the
     ------------                                                            
     payment of benefits hereunder to any Participant or his or her Eligible
     Spouse for reasons of changes in tax laws or in the event of a Change in
     Control of the Company; provided that no payment of benefits may be
     accelerated hereunder to any Participant or his or her Eligible Spouse if
     such Participant was a director of the Company on or after November 1,
     1990.

     An exception is provided for any Non-Employee Director if any income tax
     laws to which he or she is subject would cause him/her to be immediately
     taxed on amounts credited under the Plan.  Under this exception, the
     requirement that age 70 be attained before a Non-Employee Director becomes
     a Participant is automatically waived by the Committee.  Additionally,
     under this exception, the payment of all benefits under the Plan shall
     occur on the first business day which is 6 months and 10 days after the
     earlier of a Participant's resignation from the Board or death.  In the
     event of such Non-Employee Director's death, either while still an active
     member of the Board or after resignation from the Board but before receipt
     of payment from the Plan, payment shall be made to the Participant's
     Eligible Spouse on the above referenced date.

8.   CHANGE IN CONTROL. Upon, or in reasonable anticipation of, a Change in
     -----------------                                                     
     Control (as defined above), the Company shall immediately make a payment in
     cash to a trustee on such terms as the Senior Vice President, Human
     Resources, and Administration and the Senior Vice President, Finance, or
     either of them, shall deem appropriate (including such terms as are
     appropriate to

                                       5

 
     cause such payment, if possible, not to be a taxable event to Participants)
     of a sufficient amount to insure that Participants receive the payment of
     all amounts as contemplated under the Plan.

9.   GENERAL PROVISIONS.  The entire cost of benefits and administrative
     ------------------                                                 
     expenses for this Plan shall be paid by the Company.  This Plan is purely
     voluntary on the part of the Company.  The Company, by action of the Board
     or, except as limited by the Company's bylaws, the Committee, may amend,
     suspend or terminate this Plan in whole or part at any time, but no such
     amendment, suspension or termination shall adversely affect the rights of
     any Non-Employee Director or Eligible Spouse of a deceased Non-Employee
     Director with respect to Common Stock Equivalents and Dividend Equivalents
     credited prior to such amendment, suspension or termination or Dividend
     Equivalents which would otherwise have been credited in the future with
     respect to Common Stock Equivalents credited prior to such amendment,
     suspension or termination.

                                                     As Amended April 15, 1999

                                       6