Black Marks on the Back of the Page

Overview

If you see black smudges, toner marks, or streaks on the reverse side of printed pages, toner has accumulated on a component in the paper path — usually the fuser unit. This article walks you through clearing it.

Symptoms

• Black smudges or fingerprint-like marks on the back of the printed sheet
• Toner streaks running along the back of the page in the paper feed direction
• Marks that appear on every page, getting lighter or darker over time
• The front of the page prints normally

Cause

During printing, small amounts of toner can transfer onto internal rollers and the fuser unit. Over time this builds up and transfers onto the back of the next sheet that passes through.

Common triggers:

• Printing on media that is heavier or thicker than the paper type setting (toner does not fuse properly and sheds onto the rollers)
• A recent paper jam left toner residue inside the paper path
• The fuser unit is nearing end of life and is no longer gripping toner correctly

Solution

Step 1: Run a Drum Cleaning Page

A Drum Cleaning Page feeds a blank sheet through the printer, picking up loose toner from the drum and nearby surfaces.

→ How to Generate a Drum Cleaning Page

After the cleaning page, print 5–10 blank pages (send a document with empty pages to the printer). This gives the fuser additional passes to self-clean.

Check your prints. If the marks are reduced but not gone, run the cleaning page one more time.

Step 2: Verify the Paper Type Setting

If the paper type setting does not match the actual media, toner may not fuse properly and will shed onto internal rollers.

OKI C650 / C844:

1. Press Menu on the operator panel.
2. Navigate to Paper Setup > Tray 1 (or the tray you are printing from).
3. Check that Media Type matches the paper you are using (e.g., "Plain", "Heavy", "Labels").

OKI MC853 / MC873 / MC883 / ES8453 / ES8473 / ES8483:

1. Tap Device Settings on the home screen.
2. Tap Paper Setup > select the tray.
3. Verify that Media Type is correct.

Common situation: Printing on thick media (160+ gsm) with the setting on "Plain" causes poor toner adhesion. Change the setting to "Heavy" or "Ultra Heavy" to match the actual paper weight.

Step 3: Clean the Paper Path Rollers

If marks persist after the cleaning page and paper setting check:

1. Turn the printer off and unplug it. Wait 10 minutes for the fuser to cool.
2. Open the front cover.
3. Look at the rollers visible inside the paper path — especially below the fuser area.
4. Wipe any visible toner residue from the rollers with a soft, dry, lint-free cloth.
5. Close the cover, plug in, and power on.
6. Print a test page.

Important: The fuser unit is hot during and immediately after printing. Wait at least 10 minutes after powering off before touching internal components.

Step 4: Replace the Fuser Unit

If the marks continue after cleaning, the fuser roller surface has degraded and is accumulating toner permanently. Replace the fuser unit.

Check the fuser page count on the printer's status page or supplies report. If the fuser is above 80% of its rated life, replacement is the right step.

See: Replacing the Fuser Unit

Prevention

• Always match the paper type setting to the actual media loaded in the tray. This is the single most common cause of back-of-page marks.
• After clearing a paper jam, run a Drum Cleaning Page to remove toner residue left in the paper path.
• Replace the fuser unit at or near its rated page count — do not wait for visible print defects.

Applies To

All OKI printers supplied by Mediaset: C650, C844, MC853, MC873, MC883, ES8453, ES8473, ES8483, Pro9431.

Related Articles

• How to Generate a Drum Cleaning Page — First step for clearing toner residue
• Black or White Dots on Prints — For marks on the front of the page
• Periodic Dots and Horizontal Streaks — For repeating lines or bands on the front of the page
• General Print Quality Troubleshooting Guide — Start here if you are not sure what type of problem you have
• Replacing the Fuser Unit

Still Having Issues?

Contact Mediaset support if the marks continue after following these steps. Include a photo showing both sides of the printed page — this helps us confirm the issue is fuser-related.

Mediaset Support: support@mediaset.no

Category: Print Quality Issues Tags: black marks, back of page, reverse side, toner smudge, fuser, paper path, print quality, OKI Applies to: OKI C650, C844, MC853, MC873, MC883, ES8453, ES8473, ES8483, Pro9431

Last updated: March 2026