Re: ATM Re: silicone caulk adhesive strength

["Andrew Schott" <aschott@cfl.rr.com>]

I've been watching the silicon debate and would like to pitch my hat into
the ring.  In my experience there are many types of silicon goop out there
and it seems that part is being ignored by the group.

Silicon caulk has many properties for forming, sealing and paintablilty but
really isn't made for bonding surfaces together.  You don't use silicon
caulk around the door to hold the door frame in the wall.  It's designed to
stick well enough to hold it in place and remain pliable to maintain it's
seal in changing temperatures.

Silicon adhesive will bond and depending on the use, can bond very strongly
to glass.  Witness the all glass aquarium.  As a child, I used to work at a
tropical fish farm and we used to make our own all glass aquariums on the
spot.  Five sheets of glass, some silicon adhesive (I wish I could remember
the numbers on the tube as that would identify exactly what compound we
used) and some inner tube rubber bands to hold it together until the stuff
dried.  We made aquariums up to 50 gallons and never had an adhesive
failure.  I've since seen all glass aquariums up to 300 gallons assembled
the same way that are completely trusted to not rupture and blow guppies all
over the doctor's office.

One store boughten product I've found that works as well on glass is Elmer's
Sticks-All.  I've used it to build a small terrarium for a neighbor's kid
and to bond the little metal button on windshields for the rear view mirror
to mount to.  In one case I had the opportunity to test a five year old bond
on a windshield when it was broken in a crash.  I needed the button to mount
to the new windshield and tried to remove it from the broken one.  Nothing
worked until I used a large pair of  Vise Grips to rip it off and it pulled
a big chunk of glass out with it.  I had to use a blowtorch to burn the old
Sticks-All off the button before it could be prepped for remounting.

Just three more pennies and you'll have a whole nickel.


----- Original Message -----
From: "grumpa" <jdubois@essex1.com>
To: "Jim Miller" <jim@jtmiller.com>; "Albert Highe" <ahighe@ix.netcom.com>;
<atm@shore.net>
Sent: Friday, June 22, 2001 6:33 PM
Subject: Re: ATM Re: silicone caulk adhesive strength


>
> Carefully applied by professionals, with access to cleaning solvents
during
> application, silicones can and do, of course, work especially if they are
> cured by means other than moisture as are RTV silicones.  I would assume
> that the 35 ft sq attachment was not air cured with standard RTV
> crosslinking.
>
> But let's put silicones in perspective.  Amateurs using RTV silicones at
> home are risking adhesive failure.  How many of us have had our bathtub
> caulk come loose.  I certainly have (or secondaries crash down on primary
> mirrors).
>
> My scope has silicone pads under the primary and a mechanically attached
> secondary.
>
> Jule J. DuBois
>
>
> ----- Original Message -----
> From: Jim Miller <jim@jtmiller.com>
> To: Albert Highe <ahighe@ix.netcom.com>; grumpa <jdubois@essex1.com>;
> <atm@shore.net>
> Sent: Friday, June 22, 2001 5:18 PM
> Subject: Re: ATM Re: silicone caulk adhesive strength
>
>
> > 12 tons/36sq ft = 74oz/sqin.  are there any atm primaries that would
> exceed
> > this?
> >
> > [snip]
> >
> >
> > Finally, in a post to the ATM list, April 11, 1996, Dean Ketelsen
reported
> > that "100% silicone caulk you can get in any hardware store for as
little
> as
> > $2.is currently holding the [Steward Observatory Mirror Laboratory's22]
> > Magellan 6.5 meter vertically in full shear, and has been for the better
> > part of a year. Granted, it only weighs 12 tons and is supported by
about
> 36
> > square feet of bond area, but there is a huge safety factor and no one
> here
> > is worried about it."
> >
> >
> >
>
>
>