276:). This pre-sensitized plate comprises an insulating plate (epoxy resin or bakelite), adhered with a layer of copper, and coated with a varnish layer sensitized. The varnish is sensitive to UV rays, which weaken or strengthen its structure depending on whether a "positive" or "negative" process. Photolith film printed parts (usually black), inserted between the light source and the pre-sensitized plate, protect the varnish from the UV. The base copper impressed must then be engraved in a specific bath (usually ferric chloride FeCl
35:) is a device used to copy an image by illuminating a film negative with the image in direct contact with a photosensitive surface (film, paper, plate, etc.). The more common processes are negative, where clear areas in the original produce an opaque or hardened photosensitive surface, but positive processes are available. The light source is usually an
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The process shares some fundamental principles with the photographic processes, since the pattern engraved on the plate is generated by exposure to light with an image created in a contact copier using an optical mask. This procedure is comparable to the high-precision method of the version used to
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close to the silk frame. The emulsion reacts depending on the amount of light received, for that reason it is important to make some tests for determining the exposure time. Usually for a "box type" contact copier, exposure is usually not more than one minute. In the industrial type contact copiers
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process), a dynamic contact copier is used (similar to the manual action of exposing both sheets strongly bonded directly to the sunlight.). The exposition is made progressively as the twin rollers pull the two papers together (original and copy) against a source of ultraviolet light, typically a
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the passage of the silk-screen ink or the metal-etching solution. Offset printing can use either a negative plate, where the hardened, exposed photosensitive coating attracts ink and repels water, or a positive plate, where the exposed photosensitive coating decomposes or exposes the metal,
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in contact with the negative. The negative role fits the body, the lid is closed applying some pressure against the glass to prevent blur; then proceed to impress photographic paper by turning on the interior light (contact copier) or an external focus, in the last case, usually from a
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will not heal and may be subsequently washed, keep in mind that there must be no gap between the photolith and the silk, to achieve that purpose any element with enough weight may be used to press the silk against the photolith (or a vacuum pump in professional machines).
196:- covering the surface of the paper. Once exposed, the copied paper is immersed in a developer solution made from ammonia (or ammonia vapor) converting the parts of the paper not exposed to the light source to a characteristic dark violet colour (blue-line).
265:(PCBs) before being sent to production (artisanal creation ). Substantially similar to the contact printer used in photography, this variant usually uses ultraviolet lamps to impress a copper base specifically pre-sensitized.
220:(also called "Art") is placed under the frame against the emulsion. The black portions of photolith film does not let light into the relevant parts of the coated silk, therefore, in these parts
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is placed in direct contact with the printing plate and pressed with an opaque lid that sometimes has a vacuum pump that helps making a good contact. The plate comes coated with a layer of
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lamp . The original plan (on a transparent support) and the diazo paper are introduced, in perfect contact, within the pinch rollers of the contact copier. The sensitized paper, has a
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and after the transfer of information (burning) it's accomplished, then, after undergoing a developing process, the plate will be ready to be used in an offset printer.
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where the original and the photosensitive surface are pressed together against a flat glass by a grooved rubber mat connected to the vacuum source. A timer-controlled
149:. There are some models with internal light source constructed as a closed box, in which one or more lamps illuminate the negative through an opal or frosted
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insoluble; after exposure, the exposed surface was washed in water and the unexposed coating dissolved, leaving the hardened gum or gelatin to
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Burned by exposure to light parts reproduce patterns drawn on a transparent photolith film on a pre-sensitized plate (
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The contact copier is used today, particularly in the areas hobbyist, for the photoengraving of prototype
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The reproduction is done by placing the negative on top of the glass and then the photo paper with the
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generates black). It was the common mode to make prints until it began the use of the alternative
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of exactly the same size of the original. (With normal photographic non inverting processes,
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with actinic lamp placed at a distance, exposure time can be about 20 minutes.
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in which a (negative) inverted image is formed with respect to the original
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Silkscreen printing and photochemical machining originally were based on
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Hand Book on
Printing Technology (offset, Gravure, Flexo, Screen)
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407:. National Institute Of Industrial Research. pp. 222–.
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The contact copying process was used in the early days of
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used contact-rollers rather than flat-glass exposure.
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it is normally use a contact copier box with several
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photosensitive materials, where exposure to intense
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62:) light source is on the other side of the glass.
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121:The contact copier is used for duplication of
104:light made previously-soluble gum or gelatin
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452:DIAZO BLUE PRINTING MACHINE - WHITEPRINTER
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39:bulb internal or external to the device
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380:. Que Certification. pp. 244–.
280:), that removes the excess copper.
374:Eva Zeisel; Robert Sabella (2006).
355:. Hearst Magazines. pp. 216–.
347:Cryder, George R. (November 1948).
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377:Blueprints replaced by whiteprints
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42:Commercial contact printers or
442:Make firediy.fr contact copier
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401:NIIR board (1 October 2002).
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253:make printed circuit boards.
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82:, such as the manufacture of
192:coating -an impregnation of
46:usually use a pump-operated
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123:negative or positive prints
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125:obtaining what are called
113:water-attracting surface.
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477:Technical drawing tools
80:photochemical machining
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263:printed circuit boards
84:Printed circuit boards
237:offset technology, a
163:photographic enlarger
147:photographic enlarger
74:and sunlight-exposed
141:on the target while
472:Non-impact printing
437:Make contact copier
310:Heliographic copier
176:whiteprint copying
179:, (essentially a
173:In the process of
91:blue line printing
432:Making a lightbox
414:978-81-7833-087-7
387:978-0-7897-3504-1
353:Popular Mechanics
325:Diatype (machine)
210:fluorescent tubes
16:(Redirected from
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243:photoresist
186:black light
117:Photography
102:ultraviolet
72:photography
60:fluorescent
466:Categories
331:References
200:Silkscreen
169:Whiteprint
137:generates
76:blueprints
361:0032-4558
349:"Contact"
300:Blueprint
247:photolith
239:photolith
218:photolith
184:powerful
181:diazotype
290:Lightbox
284:See also
274:Bakelite
222:Emulsion
158:emulsion
106:colloids
37:actinic
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305:Ozalid
229:Offset
110:resist
270:epoxy
194:diazo
151:glass
143:white
139:white
135:black
88:diazo
409:ISBN
382:ISBN
357:ISSN
216:The
66:Uses
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235:CTF
233:In
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