[Marcus Rowland]

I just picked up a job lot of three old lenses on eBay which included a Sigma 70-210 with Nikon AF (the original motor in camera version) mount - seeing the mount in the pictures of this lot was the only reason I bought the lot - and a couple of manual zooms for other cameras. The Sigma is working well on my D50, apart from AF being a little noisy, but the outer surface of the casing is covered in a truly horrible rubbery black plastic which is sticky and slightly damaged in places. I'll be honest, I'm going to try to sell it on, but if possible I'd like to do something about the surface first.

Anyone know a way to clean this stuff and make it less sticky?

[luftfluss]

Oy, it sounds like you've run afoul of Sigma's infamous "Zen" coating.

Perhaps some alcohol or other caustic solution to remove it?

Maybe dcshooter will poke his head in here, he's so knowledgeable.

[ramseybuckeye]

I recently got a lens with the same Sigma "zen" coating on the lens and found alcohol will clean it off. I did not do a thorough job yet but it works. Just be careful, it will transfer right to the cloth you use. It may also take the lettering or markings off the lens since they were most likely put on after the zen coating. Once cleaned up I am happy so far with the performance of the 50mm macro 2.8, it's a keeper so I was happy to find a fix.

[Marcus Rowland]

I was hoping to avoid removing it completely, but maybe there's no alternative.

[goatsNdonkey]

Rubbing alcohol, which audio specialists caution people not to use to clean the rubber rollers in tape decks and some record turntables (because it can dry out the rubber) is exactly what you need. Last fall I purchased a Sigma AF zoom on which all of the rubber gripping surfaces had started to become sticky (absolutely the ONLY thing that was wrong with the lens), and a few careful treatments with rubbing alcohol completely removed the stickiness. The rubber now has more of a lustrous finish, however, not flat pebbly finish that it originally had. A very minor downside, considering the grip surfaces are not sticky anymore.

You might find the procedure a bit time consuming or tedious, but all it costs is time. I put some rubbing alcohol in a bottle cap, and then dipped a cotton swab into it and then let any excess drip back into the cap. It is good to start with one of the wider rubber areas so you get used to controlling how much the alcohol spreads out. You don't want it getting off of the rubber and seeping into cracks between other parts of the lens body. Also stay away from areas of the rubber with painted imprints, since the alcohol might remove those. After you dampen an area of the rubber with the alcohol, gently, gently, scrub the surface with the swab. Then do another area. Use a new swab when one gets more than a little gray from the stuff coming off of the rubber. You'll go through quite a few swabs. I let the lens sit and the rubber dry out between each grip ring I worked on. Then, after all three were done, I may have waited a whole day Then I looked at how it turned out and felt for remaining sticky spots. I retreated those sticky areas. Also on this second treatment, I got closer to the little bit of painted lettering that was on one of the grip rings of my Sigma lens, and I worked closer along the edges with a less-damp swab to keep alcohol from getting away from where I wanted. Again I let ieverything dry for several hours. For the last and final alcohol treatment, there were only a couple of tiny areas that needed a bit more work.

[Skodadriver]

I have a Canon EOS 100 with a sticky body handgrip. When I looked for cleaning solutions on the net I found some early AF Nikon bodies had the same problem, the Sigma "Zen coating" was mentioned. I'm afraid my action was to put some tape over the sticky area and leave it at that but I do remember reading that someone put talcum powder on the sticky areas which cured it. The talcum affecting the colour for a while but apparently will wear off eventually. Not suggesting this, just wondering if anybody might have tried it.

[Marcus Rowland]

The problem is that the affected area includes the slide of the zoom, so anything on there gets scraped if the zoom is moved. I think I'll have to go for the alcohol method.