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CTP Technology in the Modern Offset Printing Process

What is CTP?

In the traditional Offset printing process, the print design is output to the photographic film first, then the printing plate(mainly PS plate) is made. Therefore, this imaging technology is also referred to as CTF, computer to film. However, things are quite different now. In the modern printing facility, the artwork, usually in the PDF format created by the Adobe Photoshop, Adobe Illustrator, Adobe Indsign and other desktop layout applications is output directly onto the printing plate. And this tech is called CTP.

CTP Technology

CTP tech varies with the construction type of the imagesetter and the light source used to expose the plate surface. In terms of imagesetter, there are three different kinds: internal drum, external drum and flat-bed imagesetters. And the light used to expose the printing plate are mainly ultraviolet light lamps and laser diodes. The wavelength and energy of the laser diodes depend on used plate types.

CTP Plate Category

There are mainly 3 types: Photopolymer CTP plates, Silver Halogan CTP plates, and Thermal plates.

Advantages of the CTP Plate

CTP has several advantages over conventional platemaking. In CTP, one generation (transfer of film image to the printing plate) is removed from the printing process (eliminating the need for film and related developer chemicals), increasing sharpness and detail. CTP avoids potential losses in quality that may occur during film processing, including scratches in the film, and variations in the exposure. An imagesetter usually has an accuracy rate of +/-2%. Plates are produced in less time, are more consistent, and at a lower cost. CTP can also improve registration and image-to-edge repeatability over traditional methods.

In CTP, the media is registered (held in precise position) in the platesetter during imaging, and does not rely on a separately-aligned pin grid, as is the case with film. Defects due to dust, scratches or other artifacts are minimized.

CTP systems can significantly increase plate production outputs. Platesetters for newspaper production can output up to 300 12-inch (300 mm) plates per hour at 1270 DPI (dots per inch), whilst for commercial applications a CTP system could output 60 B1 plates at 2400 DPI for higher screen rulings.

Small portrait presses that typically create 1 or 2 color output can use anything from a standard laser printer, for low quality/low volume, up to a higher-end dedicated platesetter for higher quality and volume.

Disadvantage of the CTP Plate

Restricted to digital format. CTP productions require that the basis for the printed matter as well as the imposition, be digital.

Remaking of plates. If for some reason a CTP plate is damaged, if an error occurs when it’s ripped or if something has to be corrected after the plate is exposed, a completely new, imposed plate must be created

The CTP Tech in Deprintedbox

Deprintedbox uses the latest Computer to Plate technology, saving both time and money and improving print quality.

Faster Production Cycles CTP eliminates steps from the production cycle. Even in a Computer to Film (CTF) workflow it can take five steps from having the copy in digital form to having it imaged on a plate. In a CTP process four of these steps are fully removed. Each step eliminated from the process reduces the overall time required to get plates to press, getting the job to you more quickly.

Lower Printing Costs CTP eliminates the need for film by imaging the page directly from the computer to the printing plate, which, shortens production cycles and can save on material costs ultimately saving you money.

Sharper Print Quality CTP allows printing presses to print cleaner and crisper images by way of eliminating dot gain in the prepress process. In a CTP workflow, first generation dots are imaged to the plate eliminating dot gain in prepress. This gives the press more capacity for printing higher ink densities resulting in richer, better saturated colours.

Better Registration CTP excludes the use of film negatives or positives. CTP plates are imaged on highly accurate plate setting equipment on aluminium substrates that are very resistant to changes in temperature and humidity. Even imposed computer to film workflows cannot offer the accuracy and stability of registration that a CTP system can provide.

computer to plate CTP tech iexplanation

Understand The Paper Weight

U.S. Basis Weight, Metric Weight, Points

Paper weight is an important component to consider when printing. Heavier media often conveys quality and provides durability. Unfortunately, sorting through the various methods of labeling a paper’s weight is not always straightforward. First, there are three common methods for specifying paper weight and thickness: U.S. Basis Weight (Bond, Book, Index, Cover, Tag, Points, Offset ), Metric weight (GSM or G/m2) and, often interchangeable, Points or Mils (an actual Caliper reading of the paper thickness).

U.S. Basis Weight

The U.S. Basis (not basic) Weights, are the most confusing, simply because the same paper can yield different values based on the “Basis Weight” applied while manufacturing the paper. And higher values don’t always equate to heavier/thicker print media. For example, a sheet of 100lb Text paper is actually much thinner than an 80lb Cover stock.

The “Basis Weight” is defined as the weight of 500 sheets of paper in its basic unit uncut size, which means before being cut to Letter size or Legal size, the paper is weighed and categorized. The most common sizes, some of which you may recognize, are Bond, Text, Book, Cover, Index and Tag. An uncut sheet of Bond paper is 17 x 22 inches, while an uncut sheet of Cover paper is 20 x 26 inches. If 500 sheets of Bond paper (17 x 22 inches) weigh 20 lbs, then a ream of paper cut to Letter size will be labeled as 20 lb. And if 500 sheets of Cover paper (20 x 26 inches) weigh 65 lbs, then a ream of this paper trimmed to tabloid size would be marked as 65lb. This may be a lot to grasp, but don’t feel overwhelmed! Often professional printers don’t keep track of all the permutations. Based on experience from using a small subset, they have a pretty good idea of what to expect when reaching for a 24lb Bond versus a 60lb Cover versus a 110lb Index.

Paper Weight Conversion Chart

The following table serves as a reference for comparing paper weight across the different scales. The values noted in bold are the most commonly available weights.

For example, let’s say you needed to print 5,000 brochures. A common paper weight for this application might be 100lb Text. Or if you wanted just your basic copy paper for everyday use, you might want to select 24lb Bond.

Understanding paper weights and paper types in the printing industry is not easy. However, it is valuable to have a basic understanding of it, whether you work in retail, advertising, IT, finance, for a small business or in a large corporation.

US Basis Weights Caliper Metric
Bond Text Cover Index 1 Point = 0.001″ GSM (g/m2)
20 50 75
24 60 90
28 70 105
32 80 120
36 90 50 136
38 100 55 6.0 140
43 110 60 90 162
47 120 65 97 8.0 177
54 74 110 199
58 80 120 10.0 218
90 135 245
93 140 12.0 253
100 150 271
115 170 14.0 310
130 200 16.0 350
Check the more detailed paper weight conversion table here

Understand Paper Stock

To choose a paper stock correctly for your next project, you need to understand three basic things: paper type, paper weight and finishing options. These three things collectively are often understood as Paper Stock

Paper Type

Before we describe the difference between paper stocks, it’s a good idea to understand that paper basically comes one of two ways: GLOSSY or UNCOATED. It is then described by the weight and with any additional finishing options that may be applied. Paper Stock is written in terms of paper weight, paper type and any optional finish that may be applied. For example, “12 pt. Gloss” means the paper has a weight of 12 points with an inherent gloss sheen. However, “12 pt UV Gloss Coated” means that an additional finish (UV coating) has been applied.

GLOSS

Refers to the coating of the paper. Not to be confused with a post-production finishing process such as UV Coating or AQ Coating. “Gloss” simply refers to the actual gloss sheen of the paper itself, prior to printing. In finishing, however; “gloss” can describe an additional UV or AQ coating. Gloss stock may additionally be described in terms of C1S or C2S:

C1S

Coated One Side: Sheet is glossy on front, flat with no coating on back.

C2S

Coated Two Sides: Sheet is glossy on both sides.

UNCOATED

Uncoated means just that; there is no additional coating. This stock is commonly use for letterhead, envelopes and personal stationary. In this case, we recommend that you DO NOT use dark colors with high color density on this stock (black, purple, blue, brown, etc) because they may soak into the paper and possibly bleed. Use lighter colors for best results on uncoated stock.

Silk /Satin / Dull Cover

Matte, dull and silk coated stocks have a flat, unreflective or dull finish. These types of paper are frequently used to make pages easier to read that are text or type intensive. Having said that, it is still difficult for the end user to actually the difference in most instances. Dull Matte cover stock is a less expensive alternative to “Silk” or “Satin” cards because its elegant smooth finish closely resembles that of the more expensive silk or satin cards on the market.

Paper Weight

Now that you understand the two types of paper options and the various finishes they can have, it becomes much easier to understand the third and final factor: paper weight.

The weight of the paper stock, also known as caliper, is measured in 1/1000 of an inch. While their are a variety of weights, there are really only two options – COVER or TEXT.

Cover

As the name suggests, this stock is often used for the covers of brochures, booklets, calendars or products such as business cards, postcards, rack cards, collectors cards, bookmarks, hang tags, presentation folders and items requiring a durable paper stock. Cover stock is meant for products not typically meant to be folded, bent or easily torn. If bending is needed (such as with greeting or tent cards) then a score is required. Cover stock weight is described in points (pt). For example, “14 pt. Gloss Cover”. The higher the points, the thicker the paper. While this is not a complete list of cover stocks available, here is a list of the more popular:

10 pt. Cover Gloss

10 pt. Cover Soft Gloss; 10 pt. Heavy Duty Soft Cover Gloss; 10 pt. Soft Cover Gloss.
Description: Same as 14 pt Cover Gloss, but thinner for different applications.
Popular Uses: brochures, menus, flyers, door hangers, catalog covers, greeting cards, posters.
Noted Attributes: Foldable.

10 pt. Cover Matte

10 pt. Cover Soft Matte; 10 pt. Heavy Duty Matte Cover Gloss; 10 pt. Soft Cover Matte.
Description: A thick cover stock with a dull finish and soft texture.
Popular Uses: brochures, menus, flyers, door hangers, catalog covers, greeting cards, posters.
Noted Attributes: Foldable, markable, limited printer support, recycled material.

11 pt. Cover Gloss – 100lb Cover Gloss

Similar to 100 lb Gloss Text, but much thicker and heavier.
Description: Thicker than 10pt cover stock with a soft shine and texture. Similar to 100 lb Gloss Text, but much thicker and heavier. Use when durability, not just thickness is a factor.
Popular Uses: brochures, menus, flyers, door hangers, catalog covers, greeting cards, posters.
Noted Attributes: Durable.

11 pt. Cover Matte – 100lb Cover Matte

Variations Include: 11 pt. Matte Cover lb Gloss Text, but much thicker and heavier.
Description: Same as 100 lb Gloss Cover but Matte, having a dull finish and notably smooth.
Popular Uses: brochures, menus, flyers, door hangers, catalog covers, greeting cards, posters.
Noted Attributes: Durable, smooth finish, environment friendly.

14 pt. Gloss Cover

Variations Include: 14 pt. Gloss Coated; 14 pt. Heavy Duty Gloss; 14 pt. Gloss UV Coated.
Description: This is a very popular heavy duty slick surfaced gloss paper.
Popular Uses: Business cards, postcards and rackcards or any product where a thick stock and slick surface is desired.
Noted Attributes: Extra thick card stock with gloss finish, not writable or printable.

14 pt. Uncoated Cover

14 pt. Premium Uncoated Cover; 14 pt. Cover Uncoated; or similar variations refer to a heavy duty cover stock with an uncoated finish.
Description: This is a Heavy Duty Stock with no extra coating applied.
Popular Uses: as above or any product where a thick stock with no shine is desired
Noted Attributes: Mailing friendly, heavy card stock

14 pt. Dull Matte Cover

14 pt. Dull Coated; 14 pt. 14 pt Cardstock, Dull Matte Coated, 14 pt. Dull Cover, 14 pt. Matte, 14 pt. Matte Cover or any variation of the above may the same thing.
Description: A heavy duty stock dull coated for an elegant and smooth matte finish.
Popular Uses: business cards, club card flyers, postcards, hang tags, rack cards, presentation folders.
Noted Attributes: mail friendly, markable, limited printer support

14 pt. UV Gloss Cover

Variations Include: 14 pt. Ultra-Violet Gloss Stock; 14 pt. Cover High Gloss; 14 pt. Gloss UV Coated;
Description: This is a Heavy Duty Stock with “ultimate” shine that features a Fade-Resistant UV Coating. This stock is almost always picked for the business card and rack card printing we do, with postcards being very close behind.
Popular Uses: Business cards, club card flyers, postcards, hang tags, rack cards,
folders, brochures, booklets, bookmarks, greeting cards.
Noted Attributes: Extra thick card stock with ultra high gloss finish, not writable or printable.

14 pt. Gloss, AQ Coated

14 pt. Gloss Coated; 14 pt. Ultra-Violet Gloss Stock, 14 pt. Cover High Gloss, 14 pt. Heavy Duty Gloss, 14 pt. Gloss UV Coated or any variation of the above all means the same thing.
Description: This is a heavy-duty gloss stock with an additional Aqueous Coating.
Popular Uses: Business cards, club card flyers, postcards, hang tags, rack cards,
folders, brochures, booklets, bookmarks, greeting cards.
Noted Attributes: Extra thick card stock with a notable gloss sheen, not writable or printable.

Text / Book

Also known as “book” stock – Text stock gets its name because it is meant for products that often include a lot of text and can be easily folded. Products such as flyers, posters, menus, catalogs, brochures, newsletters, door hangers, letterhead, envelopes, stationery, sales sheets, are most popular. Text stock weight is described in pounds (lb). For example, “100 lb Text Gloss”. The lower the weight, the thinner the paper. While this is not a complete list of cover stocks available, here is a list of the more popular:

100 lb Gloss Book

Also called: 100 lb Text Gloss; 100 lb Gloss Text; 100 lb Book Gloss.
Description: Heavy Text Stock (25% Thicker than 80lb Gloss Text; 40% Thinner than 11pt Cover/100 lb Cover) with a soft gloss finish and Aqueous Coating.
Popular Uses: flyers, brochures, newsletters, sell sheets, mini menus, door hangers, catalog pages, posters.
Noted Attributes: Foldable.

 

100 lb Matte Book

 

Also called: 100 lb Text Matte; 100 lb Matte Text; 100 lb Book Matte.
Description: Heavy Text Stock with a soft finish and usually Dull Aqueous Coating.
Popular Uses: booklets, flyers, brochures, newsletters, sell sheets, mini menus, door hangers, catalog pages, posters.
Noted Attributes: Foldable, markable.

80 lb Matte Book

Also called: 80 lb Text Matte; 80 lb Matte Text; 80 lb Book Matte.
Description: 20% thinner than 100lb Gloss Text; 10% Thicker than 70 lb book with a soft matte finish and sometimes dull Aqueous Coating.
Popular Uses: Letterhead, envelopes, note pads, sales sheets.
Noted Attributes: Foldable, printer friendly, environment friendly.

70 lb Text Uncoated

Also called: 70 lb White Smooth; 70 lb Offset Smooth; 70 lb Book Smooth; 70 lb Opaque Smooth.
Description: High quality stock commonly used for corporate and personal stationery.
Holds color remarkably well.
Popular Uses: Letterhead, envelopes, notepad, personal stationary, sales sheets.
Noted Attributes: Foldable, printer friendly, environment friendly.

Finishing Options

Now that you understand the difference between paper types, let’s discuss the various finishing options available.

UV Coating

Ultra Violet Coating; UV; U.V.; Gloss UV, High-Gloss, Ultra-High Gloss.
A protective coating applied to a printed piece for a super glossy finish which enhances colors and provides limited protection against UV and water damaged. UV Coating is applied to a printed sheet, then bonded and cured with ultraviolet light, as opposed to Aqueous (AQ); which is cured with heat and evaporation. UV Coating tends to have a much glossier appearance (often described as a “high impact”, “ultimate shine” or “glossy” appearance that adds slightly to the overall weight of the product) than AQ Coating. The gloss feels very slick and refracts light well. Often combined with a heavy duty paper weight, the result truly looks fantastic and produces a product that won’t tear or bend easily.

AQ Coating

Aqueous Coating; Semi-Gloss Coating; Smudge-Proof Coating; Aqueous Silk.
Abbreviation for Aqueous Coating. This is available in gloss, satin (gloss + matte) and matte finishes. “Smudge-Proof”, “Smudge-Resistant”, “Water-Resistant” are all descriptive of AQ Coating. This clear coating is a semi post-production process in that it is applied directly after the inks. When the coating is applied, the product is sent through a heated air system that quickly dries the coated sheets for post production work. AQ Coating has long been an inexpensive substitute for a costly varnish application. The fast-drying, water-based, protective sheen provides a finish which boasts a very effective rub or scuff resistance (ideal for sales sheets and other material that will be handled a lot). In addition, aqueous coating protects the surface from dirt, smudges, fingerprints and scratches. AQ coating can also improve a products durability which is helpful for direct mailing, provided addresses are not directly ink-jet onto the AQ surface.

Unlike UV Coating which provides an ultra shinny high gloss finish, AQ Coating can be provided in either a semi-gloss or matte finish. For example, AQ Silk

Matte / Dull / Satin

Matte; Dull Matte; Dull Matte Coated; Satin Finish; Premium Satin.
Refers to the matte finish of AQ coating. Not to be confused with an uncoated paper type.