Rubber seal "bleeding"

[awolff280sl]

The rubber seal around my windshield bleeds black onto the cleaning rag whenever I clean my windshield glass. In other words, when cleaning my windshield, when I wipe any excess glass cleaning product off of that rubber, there is a black residue on the rag. It's not dirt or grease, but appears to be the black coloring of the rubber. No other rubber or seal on my car reacts this way. It's annoying because the black smears onto the paint and glass next to it, unless I'm very careful.
Anyone else noticed this? Do I have a "cheap" windshield seal? Is there any way to "fix" the black into the seal so this doesn't happen?

[wwheeler]

Out of curiosity, where did you get your seal and how long have you had it?

If it isn't a MB stamped product, it may be an inferior rubber compound that does not have adequate anti-oxidation properties. There are some really bad overseas rubber products. Or, it could be from a batch of rubber that was not mixed and milled correctly. Are there any small hairline cracks in the seal?

The black residue is just the rubber oxidizing from being attacked by ozone and UV and all automotive exterior rubber parts should have additives to prevent this. Most rubber will do this to some extent over time but not that severe.

You could try using 303 and maybe the sunblock in that will help.

Good luck.

[awolff280sl]

Wallace, thanks for your explanation. The windshield and seal have been in place for at least 20 years and I don't know if it is an MB seal. I cannot find small hairline cracks that you descrbe.
I followed your suggestion and will have to apply 303 on a regular basis, "SPF 40 for rubber".
It would be ideal if there was a product that could be "painted" on to give the seal a more durable protective coat. After all, this rubber is not really subject to movement.

[mdsalemi]

Andy,

A major component of black rubber--either synthetic or natural rubber, is carbon black--yes, the same stuff used as black toner in your laser printer.  This will always come off on a rag.  Every car I've ever had does the same thing.

[awolff280sl]

Actually, the bleeding is from that narrower seal between the chrome moulding and the body. The wider seal between the windshield and the chrome moulding does not bleed.