June 15, 2000

Dear BTI Shareholder:

  Brunswick Technologies, Inc. (BTI) and CertainTeed Corporation are pleased
to confirm that we have reached an agreement by which CertainTeed is
increasing its tender offer price to all BTI shareholders. Effective
immediately, CertainTeed (through its affiliate VA Acquisition Corporation) is
offering to pay $8.50 per share in cash for any and all outstanding shares of
BTI stock not already owned by them or their affiliates.

  BTI's Directors have voted unanimously to endorse CertainTeed's $8.50 offer,
concluding that this price constitutes fair value for BTI stock. The
Directors' vote was based, in part, on receipt of a written opinion of BTI's
independent financial advisor, McDonald Investments, that $8.50 per share is
fair to BTI shareholders from a financial point of view. In reaching their
decision, the Directors considered a number of possible alternative
transactions, and carefully weighed the risks and benefits of further pursuing
each of these alternatives. The Board ultimately determined that a purchase of
BTI by CertainTeed would result in fair value to BTI shareholders, and would
otherwise be in the best interests of BTI and its employees and customers.

  The increased tender offer represents nearly a 55% premium over the closing
price of BTI shares on April 14, 2000, the last trading day before CertainTeed
announced its intention to commence a tender offer. The $8.50 price reflects
about a $2.6 million increase in the total price that CertainTeed is offering
to BTI shareholders and option holders over the price offered in the original
tender.

  The BTI Directors unanimously recommend that all shareholders tender their
shares to CertainTeed in accordance with the revised terms of the tender
offer. To give shareholders ample time to take advantage of the improved
offer, CertainTeed has extended the tender offer through 12:00 midnight, New
York City time, on Thursday, June 29, 2000.

  Enclosed with this letter is BTI's supplemental Schedule 14D-9, which
contains additional information regarding BTI's evaluation and recommendation
of the revised offer and which includes the text of McDonald Investments'
written "fairness" opinion. Also enclosed is CertainTeed's Supplement to the
Offer to Purchase, which provides further details concerning the amended terms
of the tender offer.

  We ask that you read the enclosed information carefully and that you tender
your shares as soon as possible. If you are a registered holder (i.e., you own
shares in your name), then please complete the enclosed (green) Letter of
Transmittal and return it to the Depositary today with your certificates. If
you are a beneficial holder (i.e., you hold your shares through a bank or
brokerage firm), please contact your representative at your bank or brokerage
firm and ask that they tender your shares to CertainTeed. If you have already
tendered your shares with the (blue) Letter of Transmittal sent with the
original Offer to Purchase, you do not need to resend the revised (green)
Letter of Transmittal.

  If you have any questions or need assistance tendering your shares, please
call CertainTeed's information agent, Innisfree M&A Incorporated, toll-free at
1-888-750-5834, or call BTI's information agent, Morrow & Co., Inc. at 1-800-
662-5200.

  Thank you,



BRUNSWICK TECHNOLOGIES, INC.              CERTAINTEED CORPORATION




By:     /s/ Martin S. Grimnes              By:     /s/ George B. Amoss
     ------------------------------            ----------------------------
           Martin S. Grimnes                         George B. Amoss
           Chairman and CEO                          Vice President