Nozzle Check Looks Perfect but Prints Are Wrong on Epson L805/L1800: Causes, RIP Settings, and Ink Delivery Checks

Question

On my Epson L805 (similar issue may apply to the L1800), the nozzle check pattern looks perfect-clean lines and all stripes look good. But when I do real prints, some colors don't print correctly. For example, greens look off, like yellow or cyan (or maybe even black) isn't mixing right. If the nozzle check is good, what could cause bad color in real prints?

Answer

Now, to your main point: a good nozzle check does not always guarantee accurate color in real prints. A nozzle check is a controlled, light-coverage test pattern. Real images-especially greens, skin tones, gradients, and deep shadows-create different demands: higher ink coverage, faster sustained flow, and more complex mixing. That's why color problems can show up in prints even when the check pattern looks fine.

1) RIP software mixing/ICC/profile issues (very common)

Your own proposed answer is right on target: start by adjusting the mixing percentage in your RIP software. If green looks wrong, the problem often isn't "a clog," but how the RIP is building green (cyan + yellow, sometimes with additional light inks depending on configuration).

Common RIP-related causes:

• Wrong printer model selected in RIP (L805 vs L1800 profile mismatch can shift ink limits and mixing)

• Wrong ink configuration (e.g., CMYK selected but your system behaves like a different channel mapping)

• Incorrect ICC profile for the media/ink set

• Too aggressive ink limiting or linearization not done (greens can collapse into dull/dirty tones)

• Rendering intent / color management double-applied (application manages color + RIP manages color = unexpected shifts)

Practical checks:

• Print a RIP color chart / ink channel test (not just a nozzle check). You want to verify each channel contributes correctly under real coverage.

• Temporarily switch to a known-good default profile in the RIP and compare. If green suddenly improves, it's a profile/setting issue, not the printer hardware.

• In the RIP, experiment carefully with mixing percentage / ink density / linearization settings (small changes; record what you changed).

2) Dampers, backflow, and wet capping side effects (flow instability)

Your second point is also important: check dampers for backflow, especially if you do wet capping.

Why wet capping can trigger "prints bad but nozzle check good":

• Wet capping can change pressure dynamics at the head/cap interface.

• If the cap seals too strongly, or there's excess fluid, the system can pull ink backward or introduce microbubbles.

• During the nozzle check (brief, low coverage), the head can still fire cleanly. But during real prints (sustained coverage), the ink supply may not keep up consistently, causing temporary starvation in one channel-often cyan or yellow-making greens look wrong.

What to inspect:

• Damper membranes: if stiff, weak, or contaminated, they can behave inconsistently under load.

• Visible backflow in lines after parking/capping cycles (ink moving backward is a red flag).

• Microbubbles in the ink lines: tiny bubbles can pass a nozzle check but fail in real prints.

• Loose fittings or hairline cracks at connectors that only suck air during high flow.

If you suspect backflow/air:

• Ensure the ink path is airtight and properly seated.

• Check that the capping station isn't over-wet or creating unusual suction.

• Look for patterns: if color fails after the printer sits capped for a while, then improves after printing a bit, that often points to cap/damper/pressure behavior rather than clogs.

3) Partial starvation under high coverage (the "nozzle check trap")

A nozzle check uses limited ink. Real images can demand much more. So you can get:

• Perfect test pattern, but

• Color shifting mid-print, banding in certain colors, or muddy greens

Common contributors:

• Ink level/venting issues (poor venting can restrict flow only when pulling higher volume)

• Height/position of ink tanks (gravity pressure too high/too low can destabilize mixing)

• Thicker ink or temperature changes affecting viscosity and flow

4) Mechanical or alignment factors that mimic color problems

Sometimes what looks like "wrong mixing" is actually:

• Bidirectional misalignment (colors don't land perfectly on top of each other, green looks dirty or fringed)

• Paper feed/encoder issues (minor timing errors show as color contamination in detailed areas)

Try:

• Printing in uni-directional mode as a test. If color improves, alignment/timing is part of the issue.

• Running printhead alignment and checking feed calibration in your workflow.

About error codes

In your message, no printer error codes were mentioned, so there are no specific codes (numbers) I can accurately reference here. The issue you described is more consistent with workflow/RIP settings or ink delivery stability than a firmware "stop-code" event.

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