Epson Expression 1640xl Scratches

[nikonfan63]

Hello all,

I can't figure out what's causing some very deep and fairly long (ranges anywhere from half inch to two inches) scratches on the scanning glass. They're very thin in width and show up randomly around the scanning glass. I've already had the glass replaced once at a not-so-cheap fee (about $400 with parts and labor). The repairman left the old scratched glass plate with me, and I've tried my best to recreate the scratches using box cutter blades, scissors, paperclips, etc on it. I have to exert incredible force with the blade on the glass to even create a surface scratch, much less as deep as the ones that are on the scanner now. The glass is very well tempered and coated, as far as I can tell, and designed to prevent these scratches from happening.

If box cutter blades used with strong force can't make a decent scratch on the scanner glass, then dust/edges of photographic paper shouldn't do anything either. The scratches do show up in scans, and I'm using the scanner for archival, high resolution scans at a library where I'm working. Thus, I scan a high volume of photographic prints and historical documents (lettersheets, daguerreotypes, large posters, etc). But I can't think of anything that would cause scratches like this, if very sharp blades can't even reproduce the problem I'm having.

Anyone have any ideas as to what might be causing the scratches? I'm going crazy here!

[Paul Bujak]

Is it possible the sensor transit mechanism is causing the frame holding the glass to warp? Twisting the frame might set up stresses within the glass causing cracks. When the stress is relieved, the cracks would appear to be deep scratches.

[Gem Singer]

Questions that just might help solve the mystery:

1. Are the scratches on the top surface of the scanning glass, or the bottom (inside) surface?

2. You state that this scanner is located in a public library, correct?

3. Other people have access to this scanner?

4. Is it possible that someone is either purposely, or accidentally, scratching the glass?

[George Stewart]

Can you physically feel the scratches with your finger nail, or are they just visible?

Have you tried cleaning the platen with an ammonia-based product? Before everyone shoots me, sometimes one just cannot clean a glass surface with anything but ammonia. I have tried to clean the platen on my Creo with the recommended non-ammonia product and some strong mechanical action and have failed miserably. However, just a gentle wipe with a diluted ammonia product and the platen was as good as new.

I have been involved with optics fabrication and know that even a little chem-mechanical polishing (read gentle) can have a great effect on both the glass and coatings. When cleaning optics, I recommend minimal pressure and affective chemistry. If you are wiping back and forth to get the glass clean, the chemistry is not strong enough, IMHO.

[nikonfan63]

Thanks everyone for your quick responses - it's most appreciated!

Paul, as far as I can tell, the sensor transit mechanism isn't causing any stress on the chassis or glass. If they were cracks, I think the damage would be more pervasive through the depth of the glass.

The scratches are only on the top of the glass, not underneath. If I run my fingernail across it, I can definitely feel a crevice. (Whereas with the scratches I tried to recreate on the old glass, they weren't nearly as deep to the touch).

Sorry I should have mentioned earlier - it's in a state library office room behind locked doors, with very few people going in and out. I'm the only one who uses the equipment, and can't suspect anyone of sabotage or negligence. (Like I said, if I can't recreate the scratches with standard office tools, how could anyone else?)

Since it's likely I may never figure out what's causing them, what cleaning solution do you recommend to help polish out the scratches, without stripping the coating that's already on the glass? I usually use compressed air or a (dry) soft cloth to wipe off the dust before scanning (with minimal pressure, just enough to get off the particles). And isn't ammonia harmful to the coating on the glass, or is that just a tired myth?

Thanks again folks.

[Gem Singer]

Try re-creating the scratches with a carbide tipped tool (like a glass cutter), or a diamond ring, etc.

Scratches like that just don't mysteriously appear.

I strongly suspect that someone is purposely causing the damage, for whatever reason.

[Keith S. Walklet]

I am guessing it is a ring or watch band that may be the culprit.

I was surprised how easily I scratched the platen on my 4870 while wiping dust off. It was my wedding ring, a silver band with some protruding sharp edges that did the damage. I've got a six inch scratch, the result of it making contact with the glass surface as I wiped.

[Struan Gray]

Either someone with a gem in jewellery is being careless or malicious, or some of the old documents have grit in them which scratches the glass when you move them. Many mineral crystals are harder than glass, including almost all gemstones, and quartz-containing dust and grit. They will be much more effective than metal tools at scratching glass and coatings.