You just got a box of custom shirts delivered. They look fine at first glance. The design is there, the colors seem right, the sizes match the packing slip. But a screen printed shirt can hide problems that don't show up until after the first wash, and by then it's usually too late to do anything about it. Cracked prints, color bleed on polyester, fuzzy edges that weren't in the artwork, yellow marks that appeared out of nowhere. These are all signs of specific things that went wrong during production, and most of them are completely avoidable. Knowing what to look for before you hand shirts out to your team or put them on a retail shelf is what separates catching a problem early from discovering it the hard way three weeks later.

The Stretch Test: Is the Ink Actually Cured?

This is the first thing to check and the easiest to miss. Plastisol ink cures when its internal temperature reaches approximately 320°F throughout the full ink film. If the dryer was too fast, the temperature too low, or the ink deposit too thick for the belt speed, the surface of the ink can feel dry and look fine while the layer underneath is still raw. That uncured ink will crack, peel, or wash out completely after a few cycles in the laundry.

The simplest field test is to grab the printed area of the shirt and stretch it about 25 percent in each direction. On a properly cured print, the ink stretches with the fabric and returns to normal without cracking. If you see hairline fractures spider-webbing through the image when you pull the fabric, the ink didn't reach full cure. Professional shops use thermocouple probes inside the dryer to verify that the garment surface hits the target temperature for at least 10 consecutive seconds, not just a flash reading from an infrared gun pointed at the top of the ink. The surface can read 320°F while the bottom of the ink deposit is still 40 degrees short. If the shirt you're holding cracks when you stretch it, something in that curing process was off.

Color Bleed on Polyester: Dye Migration

If you ordered white or light-colored printing on a polyester or poly-blend garment and the ink has a faint pink, blue, or yellowish tint that wasn't in the design, that's dye migration. It happens because the dyes used to color polyester fabric are heat-sensitive. When the garment passes through a dryer at curing temperature, those dyes can sublimate, meaning they jump from a solid state to a gas, and migrate into the ink layer above them. White ink is the most visible victim. A white logo on a red polyester jersey slowly turning pink is the textbook example.

The migration threshold for most polyester dyes sits around 265°F to 280°F. Standard plastisol cures at 320°F. That gap is the whole problem. Shops that regularly print on polyester and performance fabrics use low-cure inks formulated to fuse at 270°F to 280°F, keeping the garment below the point where the dyes start moving. For jobs on heavily dyed polyester, a blocker base gets printed as the first layer, essentially a wall of carbon-loaded ink that blocks the migrating dyes from reaching the colors above it. Dye migration can also show up days after printing, not just on the press. If you unbox polyester shirts and the white ink looks clean, check again in 72 hours. Late-onset migration is common on garments that were stacked while still hot, trapping heat between layers long enough for the dyes to creep through. This is one of the reasons we treat polyester jobs differently than standard cotton runs, and it's a detail worth asking any printer about before they start your order.

Fuzzy Edges and Soft Detail: Screen Tension

If the edges of your print look slightly fuzzy, or fine text that was sharp in the artwork came out blurred on the shirt, the most likely cause is low screen tension. The mesh on a screen printing frame needs to be stretched tight enough to snap cleanly off the garment after the squeegee passes. When the tension drops too low, the mesh drags against the fabric instead of releasing, and the ink smears outward from the image edges.

Screen tension is measured in Newtons per centimeter. For consistent, sharp prints, most production shops target 25 to 35 N/cm across the entire screen surface, measured with a calibrated tension meter in multiple positions. Below 15 N/cm, a screen is functionally unusable for detail work. Mesh loses tension over time through repeated use, cleaning, and reclaiming. A screen that printed fine six months ago might be stretched out enough now to soften every edge it touches. Shops that maintain tension standards check their screens regularly and retire frames that can't hold above the floor limit. The ones that don't end up with a rack of low-tension screens that produce the same soft, undefined prints on every job until somebody notices. If you're comparing quotes from different printers, this is the kind of behind-the-scenes detail that separates a quality shop from a bargain one.

Scorch Marks and Yellowing

Faint brown or yellow marks on the fabric around or under the print area are scorch marks. They happen when the garment is exposed to too much heat, either in the conveyor dryer during final curing or under a flash unit between color passes on press. White and light-colored shirts show scorch marks most readily. On a white tee, even a few degrees too hot or a few seconds too long under the flash produces a visible yellow tinge that doesn't wash out.

Synthetic fabrics are especially vulnerable. Polyester has a lower heat tolerance than cotton, and pushing a poly garment through a dryer set for standard plastisol temperatures can produce a permanent sheen on the fabric surface where the fibers partially melted. On cotton, light scorching from a flash cure sometimes resembles a moisture stain and can be confused with the temporary darkening that happens when steam escapes during pressing. The test is simple: if the mark fades as the shirt cools and returns to room temperature, it was moisture. If it's still there an hour later, it's a scorch. Shops that calibrate their dryer temperature to the specific garment weight and fiber content for each job don't produce scorch marks. Shops that run the dryer at the same setting all day regardless of what's going through it will eventually burn something.

Pinholes, Smudges, and Stray Ink

A pinhole is a tiny dot of ink that appears somewhere on the shirt outside the intended print area. Smudges are larger marks, usually from ink transfer during handling. Both come down to shop discipline. Pinholes typically originate from small imperfections in the screen stencil, spots where the emulsion broke down or where debris on the screen created an opening that let ink through where it shouldn't. A single piece of lint or a dried ink particle on the mesh can create a pinhole that prints on every shirt in the run until someone catches it.

Stray ink smudges happen when an operator handles the garment before the ink is fully flashed, when ink gets on the platen and transfers to the underside or sleeve of the next shirt, or when printed shirts are stacked or folded before they're fully cooled. These are quality control problems, not technical ones. A shop running a clean press with inspected screens and a back-of-dryer inspection station catches these on the production floor. Check a few shirts from random spots in the box, not just the ones on top. Print defects that show up mid-run tend to cluster together in whatever section of the stack corresponds to the point in the run where the screen started breaking down or the platen got dirty. You can see the kind of clean, consistent output we hold ourselves to in our project gallery.

Registration: Do the Colors Line Up?

On any multicolor print, each color is printed from a separate screen that has to be aligned precisely with the others. When that alignment drifts, you get registration errors: a thin gap of exposed fabric between two colors that should be touching, or colors overlapping where they shouldn't. Slight registration variance is normal in screen printing and built into how designs are set up. Separations typically include a small amount of trapping, where adjacent colors overlap by a fraction of a millimeter to prevent gaps if the registration shifts slightly during a run.

Visible registration errors, where the gap or overlap is obvious at arm's length, usually trace back to one of two things. Either the screens weren't properly aligned during setup, or they shifted during the run. Loose screen tension is a common cause of mid-run drift because the mesh physically changes shape as it's printed through, and a screen that can't hold consistent tension will move the image gradually across a long run. Well-maintained screens within 2 N/cm of each other in tension produce consistent registration from the first shirt to the last. If the front of your order looks sharp and the registration falls apart toward the end, the screens were likely fatigued or the press needed a micro-registration adjustment that never happened.

The Wash Test

If everything above checks out on visual inspection, the final confirmation is the wash test. Take one shirt from the order, wash it inside-out on a normal warm cycle with regular detergent, and tumble dry on medium. Pull it out and look at the print. The ink should show no cracking, no peeling at the edges, and no significant color shift. It might soften slightly in hand feel, which is normal as the surface of the ink relaxes, but the image should be intact and the colors should read the same as they did before the wash.

A properly cured plastisol print can handle 50 or more wash cycles before it starts showing meaningful wear. If the ink cracks, flakes, or washes out on the first cycle, the cure was wrong and the entire order is suspect. If the colors fade dramatically, the ink was likely over-thinned with reducer to make it easier to push through the screen, sacrificing pigment density for faster throughput. If white ink on polyester picks up a color tint after washing, that's dye migration that hadn't fully expressed yet during the initial inspection. The wash test catches everything that a visual once-over can't. It takes 45 minutes and one shirt. If you're about to hand out 200 shirts at a company event or put them on a retail shelf, it's a small investment for knowing exactly what you have in those boxes.

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