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BenignBodger

On 4/13/2014 3:49 PM, wrote:
On Sun, 13 Apr 2014 10:35:51 -0700, RobertMacy
wrote:

On Sun, 13 Apr 2014 10:02:11 -0700, nestork
wrote:

Moistening the suction cups will help them keep the suction by filling
the microscopically small roughness in the rubber cup. However, water
evaporates and once it does, you're back to square one. I would use a
very light oil like WD40 on the rubber cups and/or glass before applying
the suction cups. The oil will fill the roughness just like moisture,
but it won't evaporate.

Won't the WD40 deteriorate the plastic cup, at least whether it will or
not is unknown.

Will mineral oil, olive oil, or such work?
WD40 is a crap-shoot at best. It evaporates like water, and depending
what the cup is made of, can seriously degrade it in short order.

Glass shops use glycerin on their rubber installers cups, taxi and
pizza delivery companies used glycerine on the suction cups of the
rooftop signs. It works good for sticking things to bathroom tile,
things like towel bars etc. It used to be on the instructions of many
suction mounted devices to wet the cup with one drop of
glycerine,spread thinly across the surface.

And it washes right off after you remove the suction cup - unlike RTV.

I finally managed to find a small quantity of pure glycerin -- not an easy
thing since your normal CVS/Walgreens-type pharmacy don't sell such
old-style things any more. I've re-stuck my Magellan GPS's bracket back to
the windscreen and now we'll see how long the suck lasts. It takes a
vanishingly small quantity to do the job. I used too much the first time
and the bracket just slid down the glass like a crawling slug before I even
added the weight of the electronics. Of course it didn't pop off so that
may be a good sign.