Glossary of Book Publishing Terms
Acid-free paper is paper that contains little or no acid to prevent it from yellowing from age.
The acknowledgments page is where the author recognizes those who morally supported the author or helped the author in the process of writing the book. It is typically found after the copyright page, but sometimes appears at the end of the book.
The acquisitions editor is the first editor to consider a book for publication at a traditional publishing house.
The addendum is supplemental material found near the beginning of the book to site corrections or changes made to the text. It is generally used when correcting the text would disrupt the schedule or production process.
Advance copies are books shipped by the printer to the publisher in advance of the shipping date of the main print run. They are often used for reviews and testimonials.
Annotation is a specific comment made to clarify a portion of the text. Annotations are normally placed somewhere in the page margins.
An appendix is a list of additional information, such as resources, that are not appropriate to list within the main body of the text.
Aqueous coating is a water-based clear coating on a book's cover that enhances the colors while providing protection from fingerprints, stains, smudges, and scratches.
Art paper is a quality smooth coated paper (stock) best used for printing books that require quality reproduction of photographs, artwork and other images.
Author's copies are complimentary books given to an author as part of their publishing contract. providing ten free copies is typical, but more copies may be negotiated.
Author corrections are the changes make by an author makes to the text at the proofing stage. Some contracts require that the author pay for a percentage of the cost for making such late changes.
An autobiography is a book a person writes about his or her life story.
Backlist titles are books that have been published about six months earlier. The backlist, which is usually found less predominantly in a publisher's catalog or online, is the lifeblood of most successful publishing companies.
Back matter is additional information, such as the appendix, bibliography, index, notes, and other references. Back matter typically appears after the last chapter of the book but occasionally at the end of each chapter.
Back orders are the accumulation of all book pre-sales prior to printing.
Back-of-the-room sales are direct-to-consumer non-bookstore sales made at special events where the author is the host, speaker, or a guest.
A barcode is comprised of lines of varying width contained in a small box. Barcodes are typically found on the back covers of books (and on many other products). An optical scanner reads the lines to identify the product's retail price, while also managing inventory for that title.
A bibliography is a listing of research resources and other materials used in the process of writing a book. Bibliographic references are often made in the text throughout the book.
Binding is the method used to hold the book's signatures (pages) together. Examples are saddle stitch, wire-o, perfect bound, and casebound.
A biography is a book written about part or all of another person's life.
BLAD (Book Layout and Design)
A BLAD is a brochure about a forthcoming book used to generate advance sales and media interest. The BLAD, typically 4 to 8 pages, displays the cover, a sample of the interior design, and a description of the book and author. It also includes the book's size and page number specifications, publication date, and contact and ordering information.
Bleeds (Bleeding or Bleed)
Bleeds are an extension of color or another design element that extends beyond the crop marks and off the edge of the paper. Bleeds are trimmed after printing to give the effect of printing on colored paper or to maximize the visual impact and aesthetics of the design.
Blind Embossing (blind emboss)
Blind embossing is the process of embossing without the use of ink or foils. The embossing is the same color as the paper being embossed and provides a subtle, classy, three-dimensional effect.
Bluelines are an inexpensive set of paper proof made from the negative films, showing all the colors in blue. They are used to check for typos and other errors and glitches where color is not a factor.
A blurb is a brief, compelling quote from an author or reviewer about a book found on the back cover.
Boards are the heavy stock that the casewrap is glued to in the making of a hardcover book.
A boiler plate is also referred to as a template from which a publishing contract is negotiated. It is also sometimes referred to as the basic design template from which a book is designed.
The book block is the book after is has been printed, gathered, and trimmed but not yet bound.
Aside from the social meaning, a book club is a retail booksellerÑusually online or mail orderÑthat offers a selection of discounted popular books by category. Publishers sell quantities of books to book clubs at very deep discounts. In some cases, a book club purchases the rights to print a book in a special format.
A book page a web page that contains information about a book and its author. It may include the book's cover, a summary of the book, an excerpt, purchasing information, an author bio and photo, a video trailer for the book, a blog link, and purchasing information.
A bookplate is a decorative sticker glued to the inside cover of a book that contains a line for the author's signature. Some publishers print and ship bookplates to authors to sign them. The quantity is then shipped back to the publisher, and on to the factory, where a machine affixes the bookplate at a location inside the book as specified by the publisher. Bookplates also may be used to identify numbered limited editions.
A book signing is an event, usually held at a bookstore, where the author of a book is set up at a table to autograph his or her book for customers. Book signings also occur at trade shows, speaking engagements, and other events where the author is the featured guest.
Book trade is referred to as the retail book market. It is used in distribution contracts to distinguish which sales types are exclusive to the distributor and which remain with the publisher. The book trade may consist of retailers such as Amazon and Barnes & Noble. Examples of sales excluded from the book trade are special sales, such as book clubs and mail order.
A book trailer is a video about a book and its author, usually with the author as the host. A book trailer also may be recorded in an interview fashion or completely without the author present.
The bulk is actual thickness of the paper used in producing a book. How the paper bulksÑthe thickness of the book once it has been printed and boundÑhelps the publisher determine its perceived value. It also helps the book designer to know the width of the spine for copy placement.
Camera-ready copy is the final layout of the book and/or cover.
A caption is a line of text that describes an accompanying photograph, chart, or illustration.
A casebound book is a hardcover book with a paper or cloth casewrap glued to its boards. It typically also has head and tail bands.
Casewrap is paper or cloth that is glued to the boards of a book, thus making it casebound (hardcover).
Character Count (Characters)
The character count is the total number of letters, spaces, numbers, and punctuation contained in a sentence, paragraph, or manuscript.
CIP (Cataloging in Publication)
A CIP is a block of descriptive information, typeset in a specific format, that is found on the copyright page of a book. The CIP is used by libraries to catalog books for reference purposes. This cataloging service is offered free by the Library of Congress for books that have not yet been published. A CIP is provided to publishers with a publishing program in placeÑusually at least two books per year. First-time self-publishers will find it easier to obtain a P-CIP (Publisher's Cataloging in Publication), which serves the same purpose as a CIP.
CMYK represents cyan, magenta, yellow, and key (black)Ñthe four process colors used to print a full-color image.
Coated paper is a smooth, clay-coated paper used to print books when reproducing high-quality photographs and illustrations is important.
A co-edition is the simultaneous publishing of the same book by two publishers for different markets. In most cases, co-editions involve publishers from two different countries.
Collating means organizing pages-and accounting for them-in the proper order.
The color balance is the proper intensity of colors to achieve the desired visual results when printing a book.
Color Bar (Color Guide)
A color bar is a guide printed on the edge of press sheets used by the press operator to adjust color variations prior to and during the printing process.
Color correct means to adjust the processed colors on the press to achieve the desired visual results.
Color separations are decomposed color films used to print the individual colors that comprise an image or graphic.
Comb Bind (Comb Binding)
Comb bind is a bookbinding process that uses plastic flexible teeth (like a plastic hair comb but with wider teeth) that fits into holes along the edge of the book's pages to keep them together.
Composing is the process of setting copy into type.
Contents (Table of Contents)
The contents are a listing of the chapters and subchapters of a book, including page numbers.
Co-op advertising allows a publisher to advertise with other publishers in a catalog, for example, to reduce the cost per ad.
A content editor strengthens the authorial voice and addresses organization, completeness, and the overall quality of the writing.
Continuous tone refers to illustrations and photos that have not been screened and contain gradients or varying shade tones.
Contrast is the measure of light to dark tones in an image.
Copy is the written content of a book.
Copy Editing (Copy Editor)
A copy editor addresses and corrects the grammar, punctuation, spelling, style, and consistency of a book.
Copyright is a set of exclusive rights provided to authors of original works to protect them from infringement. Copyright does not protect ideas, but it does protect how those ideas are expressed.
A copyright identifies the copyright holder of a book. It is found in the front matter.
A credit line is a line of text that identifies the copyright source for material used in a book.
Crop marks are small marks or lines on press sheets that identify where the paper is cut to the book's finished trim size.
Cropping is the removal or cutting out of part of an image.
Cyan is the color blue, one of the four process colors.
Debossing is using a die to create a depression into paper. It is the opposite of embossing.
A dedication page is a special page in the front matter of a book that expresses gratitude to an individual, group, r organization. When space is limited, the dedication and acknowledgments pages are sometimes combined.
A developmental editor works with the overall book concept and direction the writing takes to help an author reach the intended market. As the first step in the editorial process, developmental editing includes manuscript organization, strategies to ensure the writing will be complete, and suggestions for strengthening the overall quality of the writing style.
A die cut is a special tool used to shape or cut paper and other materials.
Digital proofs are made from electronic book files prior to color separations. When reviewing digital proofs, an author is able to see how his or her book's text, images, and colors will look when printed.
A distributor is a company or individual with in-house sales people or outside regional sales representatives ("rep groups") who sell books to book wholesalers and retailers.
Dot gain is the loss of detail or the increase in darkness caused by the spreading of halftone dots in the printing process.
A dot pattern is the combination of dots, in black and white or color, that make up an image.
DPI (Dots per Square Inch)
DPI is the number of dots in a square inch used to create an image.
Dummy (Dummy Book)
A dummy is a blank book, complete with cover, that is absent of any printing. It is provided by a printer to show a publisher what the finished book will look like.
Duotone refers to printing with two colors that overlap each other, such as black plus a spot color.
eBook (Electronic Book)
An eBook is an electronic edition of a book, read by a computer or special eBook reading device such as a Kindle or NOOK.
Embossing refers to creating a three-dimensional effect on paper using a die. It is the opposite of debossing.
Endnotes are notes from a chapter that are collected and printed at the end of that chapter.
An endorsement is a quote from a person, group, business, media, etc., normally found on the front cover, back cover, or in the front matter of a book, stating positive attributes about the book and/or its author. It is sometimes referred to as a Òblurb.Ó
Endpapers are two sheets of paper, often printed on one or both sides, that are used to provide a clean finished look to the inside front and back cover of a hardcover (and on occasion softcover) book. Endpapers also help hold a book together. In the front of the book, the endpapers are glued to the first page and inside front cover of the book. In the back of the book, the endpapers are glued to the last page and inside back cover of the book.
An epilogue is a closing statement found at the end of a book.
The extent is the page count of a book.
F&Gs (Folded and Gathered)
F&Gs are the printed pages of a book, gathered but not yet trimmed.
Flaps (Gatefold Flaps)
For a book jacket, the flaps are a 3-inch to 4-inch extension of the front and back cover, which are folded around the boards. For a softcover book, the flaps are a 3-inch to 4-inch extension of the front and back cover (the cover stock itself), which is then creased and folded over itself. The flaps are where information about the author and the book are printed.
A flood is a complete covering of a printed page or book cover with a varnish or other coating.
To "flop" means to reverse an image as though holding it up to a mirror.
Flush means to bring text all the way left or right.
Foil Stamping (Foil Blocking)
Foil stamping is embossing with colored foil. The die is commonly stamped onto the cloth of a hardcover book.
A font is a specific style and size of typeface, such as Times New Roman, Verdana, or Bookman, for example.
A footer is a running head that repeats a line of type at the bottom of a page. It typically repeats the chapter or title of the book.
A footnote is a devoted area at the bottom of a page where notes from that page are displayed.
A foreword is written by someone other than the author to relay background or explanatory information about author or the book.
Four-Color Process (4-Color)
Four-color process is printing using the four process colors (cyan, magenta, yellow, and black) to produce a full-color image.
A French fold is the where the jacket of a book has been folded to produce jacket flaps and also folded over at the top and bottom to provide a clean finished look.
The front matter comprises all pages prior to the main body text.
FTP (File Transfer Protocol)
FTP is the electronic transfer of information, usually book design files, from two networked computers.
Galley (Bound Galley)
A galley is a pre-published book that is a bound paperback and used for marketing purposes.
A gatefold is paper that has been folded inward from the edges to meet in the center. It typically is inserted between the signatures of a book. The reader unfolds the gatefold to reveal art or other graphics.
Ghostwriting occurs when someone writes a book for someone else. This service is performed by a ghostwriter.
A glossary is an alphabetized listing, found in the back matter of a book, that defines words, phrases, and expressions used in the book.
Gilding is gold leaf or powder applied to the outside edges of a bound book.
Gloss art is paper stock applied with a shiny coating prior to printing.
A gloss cover is a cover that has been applied with a shiny coating prior to printing.
Grain direction is the direction in which the paper fibers run.
Grayscale refers to varying values or shades of black to white.
GSM (Grams per Square Meter)
GSM is the metric weight of paper common to overseas printing.
The gutter is the point at which the paper of a bound book begins to curve sharply toward the center.
Halftones (Halftone Dots)
Halftones are dot patterns that create the effect of a continuous tone image. The fewer the dots the lighter the area.
Half Title Page
The half-title page contains only the title and not the subtitle of the book. It precedes the title page.
A hard copy is a physical printout of a book's manuscript during any stage of production.
A hardcover or casebound book is bound by boards that are typically paper or cloth wrapped and finished with head and tail bands.
Head and Tail Bands
Head and tail bands are decorative strips of cloth glued at the top and bottom of a book's spine.
The header is a margin at the top of page that spotlights a title or message.
House Stock (House Paper)
House stock is a selection of papers frequently used by printers. It is purchased in quantity at discounted prices and often results in a publisher receiving the best deal possible.
An imprint is a subsidiary of a publishing company usually purchased or developed to serve specific niches.
An index is a list of words at the end of a book that guides a reader to the specific pages on which subjects appear in the main body of the text.
Initial Print Run
The initial print run is the first printing of a new book.
Interior graphics are any imagesÑsuch as photographs, drawings or artÑthat appear in a book.
ISBN (International Standard Book Number)
An ISBN is your publishing "social security number." ItÕs a 13-digit string of numbers that identifies your book or audiobook, as well as your status as the publisher.
Kerning is changing the distance between characters. It is useful for adjusting the text while designing a book.
A keyline is a shape, usually a box, used as a placeholder for photographs, drawings, art, etc.
A knock-out is the masking of an image.
Keywords are researched single words or phrase used to generate traffic to a website.
Lamination is the application of a thin plastic coating to the cover of a book or jacket that helps prevent scuffing while enhancing the colors.
Landscape is a book format in which the book is wider than it is tall.
A line editor addresses the author's voice as well as grammar, punctuation, spelling, and consistency. He or she may also make suggestions regarding character, plot, dialogue, and pacing.
A literary agent represents an author to a publisher. The agent negotiates the publishing contract on behalf of the author and typically earns a 10 to 15% commission.
Magenta is the dark purplish-red color among the four main process colors.
Make-ready is the final phase in which a book is ready to go on press.
The manuscript is the unedited book as written by the author. If the book will contain images, they may appear in the manuscript or be identified with placeholders such as "photograph of 'x' here."
Marketing (Book Marketing)
Book marketing involves a comprehensive overview of your potential book sales and promotions activities.
A mass-market paperback is an inexpensive paperback book typically printed after the book has experienced success as a trade paperback book.
Margins are areas outside of the designated printed area.
Matte art is paper that is coated with a dull surface.
A mock-up is a rough (and sometimes partial) visual concept for a book's design and/or packaging.
Moire (Moire Pattern)
A moire pattern is an undesirable wavy pattern found in a printed image. It is caused by scanning a previously printed halftone and then printing it again with more halftones. The result is a double set of halftones or "dots-over-dots."
News Wire Distribution
News wire distribution is the circulation of stories among various media.
A niche is a targeted market of a particular topic. The tighter the niche the more focused the market.
Offset printing is the traditional and most common book printing method. It is the process of pressing rollers coated with ink onto the paper.
On-demand printing is a digital book manufacturing process that allows one book at a time to be printed and bound.
An on-demand publisher sells editorial, design, marketing and other packages, and prints and ships books on-demand.
Opacity is the amount one can see through a sheet of paper.
An orphan is the short ending of a paragraph at the bottom or top of a page.
Out of Print (OOP)
An out-of-print book is one that is no longer available from the publisher or through its distribution channels. A publisher will have no immediate plans to bring the book back into print. Some authors' contracts stipulate that after a book is out of print the author may request that the rights be returned to him or her.
The overrun are the number of copies printed over the requested amount. 5% overrun is typical. Overruns are typically priced less per unit than the main print run.
The page count is the total number of pages in a book, including front matter, back matter, and all blank pages.
Pagination is the organization and numbering of a book's pages.
Pantone is a company that provides the standard color-matching system for designing and printing.
Page proofs are printouts of a book's paginated pages just prior to finalizing the files for printing. They're used to make final checks before a book goes to the printer. They're also used for indexing.
P-CIP (Publisher's Cataloging-in-Publication)
A P-CIP is a block of descriptive information, typeset in a specific format, that is found on the copyright page of a book. A P-CIP is used by libraries to catalog books for reference purposes. Generally speaking, a P-CIP is for self-published authors, whereas a CIP is for established publishers. A P-CIP is often typeset for a fee by a third party.
PDF (Portable Document Format)
A PDF is a common independent document platform created by Adobe. It can contain text, graphics, drawings, etc., and is often used to print pages of a designed book for editing.
Perfect Bound (Perfect Bind)
A perfect bound book is a softcover book where the edge of the spine has been applied with glue and the cover wrapped around it.
A photo credit is a credit line given to the photographer. It typically is found next to the photograph or on a credits page.
PLC (Paper Laminated Cover)
A PLC is paper that has been glued and wrapped around the boards of a casebound book. Depending upon the design, it may or may not need a jacket. For example, the PLC may be printed in color with the title of the book alone and then jacketed or printed in full color without a jacket.
A podcast is a series of audio or video broadcasts for downloading to a personal computer or audio player.
Portrait is a book format in which the book is taller than it is wide.
The preface is an introduction written by the book's author to explain why or how the book was written. It precedes the foreword in a book.
Prepress is the transition of a book design to readiness for final printing.
Printing Plates (Plates)
Printing plates apply ink to the pages of a book during the printing process.
Print-on-demand is a digital book manufacturing process that allows one book to be printed and bound at a time.
Print-ready means the book's design files have met all criteria for commencing the printing process.
The print run is the total number of books printed at one time.
Process colors are the four basic colors that produce a full-color image. The colors are cyan (blue), magenta (red), yellow and black.
Proofs are provided by a printer as a final check before printing.
A proofreader looks mainly for correct grammar, punctuation, and spelling. The proofreader also may catch errors made during the interior layout process and before the manuscript is finalized for printing.
Publication Date (Pub Date)
The publication date is the date when a book is expected to be stocked in stores and reviews are expected to begin to appear.
A publicist promotes a book and its author through various services, from writing press releases to scheduling book signings.
Remainders are a publisher's excess stock or slightly damaged books. They often are sold to third-party remainder dealers for a fraction of the retail price. Remainder dealers then sell quantities of remaindered books to various retailers. CIROBE is the largest trade show for remainder dealers.
A rep group is a group of book salespeople who sell a publisher or distributor's books to retailers. Each rep group covers a specific region, such as Northwest, Southeast, etc., on an exclusive basis.
Resolution is the quality of an image as measured by its DPI (dots per inch).
Returns are books that are returned to the publisher or distributor in exchange for a full refund.
RGB stands for red, green, and blue. These are the three primary colors in which we view an image. They are converted to the four process colors (CMYK) for printing a book.
A royalty is a percentage of a publisher's sales of a book that is paid to its author. 8%-10% is a typical royalty on the retail price. Escalating royalties may be negotiated based upon benchmarks on the number of copies sold. Some publishing contracts calculate royalties on "net receipts" (the amount the publisher actually receives).
A royalty advance is a negotiated amount paid to an author prior to publishing a book. Royalties from the sale of the author's books are deducted from the royalty advance until it is earned out.
A run-on is the number of copies printed over the requested amount. A 5% run-on is typical. Run-ons are typically priced less per unit than the main print run.
A running head is a repeating line of type that appears at the top of a page. It typically repeats the chapter's name or the title of the book.
Saddle stitch is a bookbinding method that uses staples.
Sans serif is a typeface that does not have small strokes at the ends of individual letters.
A self-mailer is a mailing pieceÑusually used for advertising, sales, or promotions-that can be mailed without an envelope.
Self-publishing is the process in which an author publishes a book without the involvement or controls of a publisher, vanity press, on-demand publisher, or other third party.
A sell sheet is a single-page document that is used to inform sales representatives about a forthcoming book. The contents also may be used as a BLAD ("book layout and design" brochure) and for other marketing pieces.
SEO (Search Engine Optimization)
SEO is the process of naturally raising the visual profile of a site, usually by employing high-demand keywords or search phrases.
Separations are decomposed color films used to print the individual colors that comprise an image or graphic.
Serif is a typeface that has small strokes at the ends of individual letters.
Sheet-Fed Offset Printing
Sheet-fed offset printing is a method of printing books in which the paper is either made or cut to the exact size needed.
A signature is a large printed sheet that when folded becomes a group of pages in a book. The book's signatures are then gathered and bound to make a finished copy of the book.
A slipcase is a special printed or cloth-wrapped box used to enclose a book. Slipcases are generally used for special edition books.
The slush pile contains unsolicited manuscript submissions to publishers.
A small press is a company that publishes books to niche markets.
Social networking allows users to create a profile and form communities on special sites. Examples of social networking sites include Facebook, MySpace, Ning, Tumblr, and Twitter.
Special sales are books sold to non-traditional bookstore markets in large qualities at large discounts. Examples include gift stores, clubs, mail order companies, and other catalogers.
Spoilage refers to books that are not sellable at the end of the printing process.
A spot color is a single color printed on its own.
Spot UV (Ultra Violet)
Spot UV is used to highlight specific printed areas of a book's cover.
A spread refers to the left and right pages of an open book.
A stet is a notation used by an editor or proofreader to indicate a correction he or she did not intend to make.
Stock is the paper used to print books. A house stock is one that a printer inventories regularly.
A style sheet is a document an editor uses to follow the grammatical and other editorial rules established by the publisher.
Subsidiary rights are found in publishing contracts. They include foreign language, film and television, paperback, audio, book club, serial rights, and other rights. "Second serial rights" follows publication.
Subsidy publishing is the sharing of publishing costs between the author and the publisher. Arrangements include dividing responsibilities for the various services as well as requiring the author to purchase a specific number of copies.
Table of Contents (TOC)
The table of contents lists the sections and chapters of a book, along with their page numbers.
A tear sheet is a page removed from a newspaper or magazine to show howÑand to prove thatÑan advertisement or review was printed.
A testimonial is a quote from a person or group, typically found on the front cover, back cover, or in the front matter of a book, testifying to the accuracy or positive attributes of a book and/or its author.
The title page contains the book's title and subtitle and often the publisher's name and logo.
A trade book is one that has been published for the general retail market.
To trap means to print one ink over another ink.
Trim marks identify where the sheet will be trimmed.
Trim size refers to the vertical and horizontal measurements of a book's finished size.
A typeface is a set of fonts that represents a complete set of characters that form a type style family.
A template is a standard layout used by a graphic designer to design a book, a book cover, marketing and promotional materials, etc.
Tints are the shade of a particular color.
A tip-in is a special page or group of pages inserted into a specific location in a book prior to binding.
Tissue overlay is a transparent paper tipped into a book to protect a page with artwork on it.
A trade paperback is a softcover edition of a book that is published prior to the book's publication as a mass market paperback.
The trim size is the final size of a printed and bound book.
Typesetting is the interior design process of a book.
An unsolicited manuscript is one that an author sends to a publisher without requesting prior permission.
UV coating is a liquid applied to a book's cover that is cured with ultraviolet light. It is used to protect the cover and enhance its colors.
Value added is a way to increase the perceived value of a book to the buyer by adding additional features. Examples include colorful tip-ins and special binding. Books also may be paired with other books and products to increase value.
Varnish is a clear liquid applied after the book cover has been printed to protect the cover and give it a glossy finish.
Vanity Press (Vanity Publisher)
A vanity press is a publisher that requires the author to pay for all of a book's publishing expenses. In return, the author receives a royalty and may have to relinquish his or her book rights to the vanity press.
Virtual Book Tour (VBT)
A virtual book tour is an online "blitz" promotional campaign for a book. The tour may include teleseminars, podcasts, webinars, radio interviews, guest blog writing, and other tactics for reaching target audiences over a specific time frame.
A watermark is an image or pattern in paper that is added during the paper manufacturing process to identify the manufacturer.
A webring is a group of websites centered around a particular theme.
A webinar is an interactive online seminar.
Web Offset Printing
Web offset printing is the process of pressing rollers coated with ink onto a continuous roll of paper.
Wire-o is a binding process that winds circular double-wire strips through holes that are punched along the binding edge of a book.
A wholesaler provides books to retailers. Wholesalers purchase books at discounts from publishers and hen sell them to retailers for a profit.
Wholesale Book Distributor
A wholesale book distributor represents publishers by actively selling their books into retail channels.
Woodfree is paper made from chemical pulp. The process involves the chemical breakdown of wood fibers to change the paper's characteristics to reduce yellowing.