Paper platen leaving impression on prints - Epson 9890

[NeilPrintArt]

I know other people have described this issue in the past, just not sure if anyone has come up with a solution?
Using a 9890 and printing to gloss media (Canson Platine, Ilford Fibre Silk, changing media doesn't help). Getting bands or ridges that run vertically up the entire length of the print. Similar to the dreaded 'pizza wheel' effect that others have described, but this is a solid ridge or band. On the front of print it appears as a faint but visible, parallel, consistent ridge, kind of similar to paper 'cockling' effect but straighter and more even.
Back of the print reveals pressure marks that are the obvious cause. These pressure marks/lines/grooves run vertically and consistently up the print, parallel to the paper feed direction. The pressure marks seem to be caused by the hard plastic ridges on the back platen area of the machine.
I am attached 3 images, one showing the front of the print, second showing the pressure marks on the back of the paper and the third highlighting the plastic ridges I am referring too. All the marks line up perfectly with these.
I have tried adjusting platen gap, paper thickness, drying time per pass, none of these seem to help. Changing the paper suction to min (-4) helps but doesn't eliminate the problem.
I have been using the machine for a few years but only recently became aware of this issue, which, like I said earlier, only seems to effect gloss media?
Any help or suggestions would be gratefully received!!     

[mearussi]

I've own both the 4800 and 7800 which have similar ridges and never noticed this kind of problem, but I'll keep a lookout for it in the future. 
Do you have any old prints that you can check to see how long you've had this problem? Have you asked Epson?

[NeilPrintArt]

I am still really baffled by this and have spent days trying to figure it out.

As previously mentioned, I noticed clear parallel ridges appearing on the surface of gloss paper prints. Closer inspection of the prints reveal 'impressions' or 'pressure marks' on the back of the prints. These appear to be caused by the plastic ridges on the back platen of my 9890.

I went and looked at some old prints (thanks mearussi) and discovered the impressions on the backs of old glossy paper prints dating back at least a year. These lines are not noticeable at a quick glance, but when held at a sharp angle to a light source they become apparent (and then impossible to un-see!). The older prints only have very faint, hardly discernible, ridges on the surface of the prints, but I think that is because I was using Hahnemuhle PhotoRag Baryta, which seems to be less effected.

Recently I have been using Canson Platine Fibre and Felix Schoeller True Rag Silk (both these papers are much 'softer' and more pliable in the hand) and the pressure marks are much more noticeable and not at all acceptable.

This only seems to effect gloss papers. Matte papers still show very faint impression on the back, but not enough to impress surface.

Paper or roll feed doesn't make a difference
Resolution, platen gap, drying time per pass - has no apparent effect
Reducing the paper suction to min (-4/36%) helps a lot
I tried covering the plastic ridges of the back platen with masking tape. (see pic below) This certainly reduced the scratching, but the 'pressure ridge' is still there.

Attached are pics of the back of a sheet and back of a roll - both showing pressure ridges
Also attached is another pic of a surface of a print showing visible ridge.

My 9800 has a back platen which is flat and smooth and certainly this has never occurred on that machine. Is this a serious design flaw on the part of Epson? 

To summarize....
I assume that the pressure marks are caused by the back platen. Could it be anything else? (they are definitely not there before the paper is loaded)
I assume the the resultant ridge is a permanent defect?
The effect is most noticeable on 'soft' gloss paper like Canson Platine.     

Has anybody ever seen this before? Any suggestions?

Neil

[mearussi]

Maybe you just have an abnormally powerful suction. If so you'll just have to live with it  and learn to work around it. I've recently switched from the Canson Platine to the new Canson Baryta Prestige. Since the paper base is mostly Alpha Cellulose instead of cotton it is much stiffer and harder than cotton and so I doubt that it would take any impression from your rollers. I prefer it now to the Platine because I'm getting a noticeably better image quality, so I think you might like it as well. It also has the best anti-reflective surface for a "glossy" paper I've seen. At $193 for a 24"x50' roll it's not cheap but it might solve your problem.