Tolerancing Coloring Inward Presswork Using Company Ink Density

Background data - ink celluloid thickness & corporation ink density

Offset printing presses are designed to lay downwards a celluloid of ink, inwards the presence of water, onto a substrate - commonly paper. The ink forms the icon spell the "water," to a greater extent than accurately outpouring solution," prevents the non-image surface area on the printing plate from accepting ink. For the procedure to work, in that place needs to hold out a critical ink/water residue alongside the destination of having an ink celluloid thickness betwixt ane micron.

If the ink celluloid thickness is likewise great, the resultant tin hold out "ink tailing/misting." In addition, the non-image background may convey on ink resulting inwards "catch-up" (sometimes false for "scumming"):
On the other hand, if the ink celluloid thickness is likewise thin, the resultant tin hold out a breakdown of the ink on the canvas causing depression contrast, loss of sharpness, in addition to mottle:
So, from a color tolerancing indicate of view, because the component subdivision of ink is to filter calorie-free in addition to let us to run into color in addition to because its thickness also effects the integrity of the printing procedure - ink celluloid thickness on the canvas becomes an of import metric to stair out in addition to tolerance inwards presswork.Top: CMYK at high ink celluloid thickness/solid ink density.
Bottom: CMYK at depression ink celluloid thickness/solid ink density.
There is no practical means to straight stair out the ink celluloid thickness on a press sheet. However, in that place is an indirect means in addition to that is to stair out the corporation ink density (SID) using an musical instrument called a densitometer.

Color tolerancing through densitometry

Measuring SIDs inwards the corporation ink patches inwards the color bar alongside a densitometer does non truly render data most the color beingness printed. However, because it indirectly provides data most ink celluloid thickness (which impacts color in addition to note reproduction) SID values are valuable for procedure command in addition to defining variation during a press run where the instrument, ink, in addition to substrate rest the same.North American (Status-T) high-low specifications for acceptable SID variations measured alongside ink dry.
Top: Commercial sheetfed, Middle: Magazine/heatset web,
Bottom: Newsprint/coldset web.
From a color indicate of view, the supposition is that all 3 chromatic colors vary inwards the same direction in addition to thence rest inwards relative balance. When that happens in that place is a shift inwards color saturation (higher SIDs = higher saturation) equally good equally note reproduction (higher SIDs = higher dot gain/TVI). If ane color, e.g. Cyan, is at the maximum depression indicate spell roughly other color, e.g. Magenta, is at the maximum high in addition to then the resultant may hold out a visible color bias inwards the presswork.
Typical SID variation inwards presswork graphed yesteryear mensuration color bar patches every 10 sheets through the press run.
While a densitometer tin also hold out used to monitor variations inwards non-process, i.e. spot/Pantone colors, commonly a printed sample of the target color, including a high/low density tolerance reference, is used instead since this helps both impress specifier in addition to supplier visualize the acceptable attain of color alter equally SIDs naturally vary during the press run.Checking for topographic point color variation
Addendum: Densitometer laid - "Status" condition

Densitometers are laid yesteryear their manufacturers to an manufacture defined "Status" which defines the total answer of the musical instrument including calorie-free source, optics, filtering, in addition to receptor for given wavelength. The primary responses for the impress describe of piece of employment organization are "Status E" in addition to "Status T" (ANSI PH2.18 in addition to DIN 16536). In addition, densitometers are available alongside or without polarizing filters. Dry ink density readings from polarizing in addition to unpolarized densitometers equally good equally those laid to Status due east vs Status T volition not agree. Typically European instruments are laid to Status due east in addition to role polarizing filters spell North American instruments are laid to Status T in addition to create non role polarizing filters.

The of import affair to hold out aware of is that if SID data is shared exterior of the printshop - in addition to then the Status of the instruments that were used to create upward one's take away heed SID values must hold out known. In addition, it is critical that all instruments inside the printshop are laid to the same Status. In North America, where many of the presses in addition to their closed-loop color command systems are from Europe, it is non odd to detect the press laid to Status due east polarized spell the handhelds are laid to Status T unpolarized which tin easily resultant inwards quite a fleck of confusion inwards production.