Fabric defects · Dyeing and printing - Printing defects in fabric: register, streaks and smears

Printing puts color on fabric in a pattern. A printing defect is a fault in that pattern: a color out of place, a streak, a smear, a stain, or color that is missing.

A printed pattern with one row of motifs out of register, their colors not lined up, outlined in cyan.

What ConductVision Textile records

ConductVision Textile is designed to flag each defect with its place on the roll, its size, its points and a still image. Your inspector names the defect and confirms or dismisses it.

On the defect map in the roll report, a printing defect is a spot, or a line along the roll where it streaks.

Fabric inspectionDefects, points and a final points forecast

What printing defects are

Cotton Incorporated describes textile printing as "localized dyeing," and warns that the color must go on right the first time, "because printing defects cannot be repaired" ¹. Color can be printed by rotary screen, roller, digital or heat transfer methods ².

A U.S. federal glossary of fabric imperfections defines off-register printing as "pattern displacement caused by improper alignment of printing rolls" and a doctor streak as "a wavy white or colored streak in the warp direction on printed cloth." A misprint, it says, is self-descriptive ³.

Printing defects by name

Roller scratches, snaps, lifts and scumming come from roller printing, where a blade called the doctor scrapes surplus color off an engraved roller ⁴. Glue streaks, color out and screen faults are on Cotton Incorporated's list of screen printing defects ¹.

Printing defects by name
Defect	What it is
Out of register	Colors that do not line up with each other or with the design. Cotton Incorporated traces its example to "print rolls not being synchronized to bring all parts of the design into proper position" ⁵. Fabric distortion, or "shift," is a major contributor ¹, and carelessness alone can put a print of more than one color out of register ⁶.
Doctor streaks	A wavy line along the fabric where color got past the doctor blade. Cotton Incorporated's example came from "a bent or damaged doctor blade not cleaning properly, allowing color to escape" ⁵. The doctor moves to and fro as it works, and that "traverse" motion makes the streak wavy ⁴.
Roller scratches	Straight lines along the fabric from a scratch on the engraved roller. Grit in the color, sand or metal, cuts the roller, and streaks from roller scratches "are always straight" ⁴. Goldberg also traces streaks in prints to scratches on engraved rollers and small nicks in doctor blades ⁶.
Snaps and snappers	A hard particle lodges under the doctor blade and holds it off the roller, so color escapes on either side of it ⁵. Large double stripes of color run up the piece, and the color reaches the cloth "in the form of a smudgy stripe." Loose threads are one of the commonest causes, and bits of dried color or starch that was not mixed in properly can cause them too ⁴.
Lifts	Small marks of color, very like tiny snappers, that usually repeat at regular intervals. When they repeat at a distance equal to the roller's circumference, a particle of steel stuck in the roller lifts the doctor on every turn ⁴.
Scumming	A film of color over the whole surface of the cloth, because the smooth, unengraved surface of the roller was not cleaned well enough. A rough or badly set doctor, a rough roller surface or faulty color can cause it ⁴.
Color smear	Color smeared out of the engraved design ⁵. Cotton Incorporated lists color smear among screen printing defects too ¹.
Bleeding and flushing	Color that spreads past the edge of its motif. The thickener in a print paste holds each color in place "without the color bleeding onto the other" ¹. In vat dye printing, flushing is "a horizontal wicking of the print motif," and a thickener without enough solids to keep the print sharp is one cause ⁷.
Color out	Part of the design without its color, because color ran low in the reservoir ⁵. In screen printing, color out comes "from a lack of print paste" ¹.
Screen faults	Pinholes in a screen, and damage to a screen that leads to misprints, are on Cotton Incorporated's list of screen printing defects ¹. A screen also clogs when paste builds up in its openings, or when lint from the fabric sticks to it ⁸.
Glue streaks	Streaks of glue from the rubber blanket, another screen printing defect on the same list ¹.
Specks	Dots of color where pigment particles clump into large agglomerates. They show most in pale shades, and only after fixation ⁷. Specks can also block a screen ⁸.
Scrimps	White places where a crease in the fabric ran through the print machine ⁴. When the crease is opened, the pattern is broken ⁵.
Print machine stop	A smudge where excess print paste marked the fabric while the machine stood ⁵.
Back-greige seam impression	A seam in the back greige, or cushion fabric, leaves its impression in the print by making the substrate thicker ⁵.
Mottled printing	A blotchy or spotted look ³, from color or dye unevenly applied to or accepted by the fabric ⁵. Knecht and Fothergill trace uneven printing to the cloth, the rollers, the color or the working of the machine ⁴, and foam in the paste gives uneven or light print color ¹.
Mark-off	Stored prints that still hold fixation chemicals may mark off, especially in humid conditions ⁹.
Poor discharge	In discharge printing, fabric is dyed first and then printed with a paste whose chemical destroys one of the dyes ². When the ground shade does not discharge well, the usual cause is "using a dyestuff that is not recommended for the discharge procedure" ⁷.
Water spots	Spots where steam condensate dripped onto the fabric in the steamer before the dye was fixed ⁷.

What causes printing defects

What causes printing defects
Stage	What happens	What to check
Preparation	Any variability in the prepared fabric shows up in the print, and size left on woven goods can keep print color from penetrating and fixing ¹. Lime left in the cloth after bleaching gives light, granular patches ⁴.	Even preparation, size removal, and lime washed out after bleaching
Fabric stability	Fabric that distorts, or shifts, puts colors out of register. Woven fabrics are typically much more stable than knits ¹.	Fabric stability, above all in knits
Print paste	Paste of the wrong viscosity, contaminated color or foam spoils the print ^{8, 1}. Colors that are badly mixed, or that separate as they are worked, print unevenly ⁴.	Paste viscosity, mixing and foam
Rollers and doctor blades	Scratches on engraved rollers and nicks in doctor blades give streaks ⁶. Grit in the color, and steel filings left from sharpening the doctor, cause both ⁴.	Roller surfaces, doctor edges, and color strained free of grit
Machine setting	More roller pressure at one end than the other prints one side darker. A dark or light band up the middle comes from the lapping, the layers of cloth wound round the pressure bowl, or from a long roller springing at the center ⁴.	Roller pressure from end to end, and the lapping
Screens	Pinholes or damage in a screen, or a mesh clogged with paste or lint ^{1, 8}.	Screens, mesh and lint removal
Running the machine	Carelessness can put a print of more than one color out of register ⁶, and creased fabric running through the machine prints white places ⁴.	Register, and fabric running in flat
Steaming and storage	Condensate from steam coils cut off by clogged traps drips onto the fabric before the dye is fixed ⁷. Stored prints that still hold fixation chemicals may mark off in humid conditions ⁹.	Steam traps, and dry storage
Washing off	Too little soaping after printing can leave poor colorfastness ⁶.	Soaping after printing

Where printing defects show on a roll

Streaks run along the fabric. Knecht and Fothergill describe them as fine lines "running along the piece in a direction more or less parallel to its selvedges" ⁴, and the federal glossary puts the doctor streak "in the warp direction on printed cloth" ³.

Some printing defects repeat. Lifts from steel in a roller recur at a distance "corresponding to the circumference of the roller," and so do weak places from engraving of uneven depth. Lime stains, by contrast, "occur at irregular intervals" ⁴.

Across the width, one side printed darker than the other points to uneven roller pressure, and a dark or light band up the middle points to the lapping or a long roller springing ⁴.

Defect positionWhat a defect's place on the roll points to

How printing defects count

Cotton Incorporated's grading guide gives printing defects a category of their own ¹⁰, and its defect glossary rates every one of its printing examples major ⁵. The guide defines a major defect as one severe enough, if exposed, to make the end item a second ¹⁰.

A streak that runs on along the roll is a running defect. One buyer manual, which follows the 4-point system of ASTM D5430, gives up to 4 points to each linear yard or metre in which a continuous running defect exceeds 9 inches, and no linear yard gets more than 4 points ¹¹. A spot is scored by its length: 1 point up to 3 inches, 2 points over 3 up to 6 inches, 3 points over 6 up to 9 inches and 4 points over 9 inches ¹².

The same manual sets the least amount of fabric to inspect for each pattern, colorway or print ¹¹.

Sources

Pilot - How a pilot starts

We start with recorded video of your inspection frame and agree with your team on one fabric to test. The pilot runs for a set time, and before it starts we agree on what counts as success. For each defect it marks, ConductVision saves a still image and its place on the roll on your network for your inspector to check.

You bring: Recorded video of fabric running over your inspection frame
We set up: One fabric, and the limit you grade it against
You get: Marked defects, running points and a final points forecast for each roll, and a results report checked against what we agreed

One question to start with

Which printed fabric shows printing defects most often?

Plan a pilot