In article
,
mike wrote:

On Sep 24, 7:35*pm, jeff_wisnia
wrote:

Whatever had been holding it in place for about 60 years finally gave up
and let go. The remains of it in the recess are frangible and feel like
some sort of "plaster".

Burn some and smell the smoke. If it's sulfur, you will know.


could have been grout.

Before WWI, melted Sulphur was used to attach Iron and Bronze
to stone, it expands as it cools, and seems last a _long_ time,
given examples are still attached.

But as others point out, Goop is the stuff for today, and my goto
choice.

Melted Sulfur. I think it's still used. In 1974 I lived a year in
Sweden. The Swedes build for the Ages - I think they plan to stay.

At a summer house near Stockholm, there was a galvanized iron ring
attached firmly to a large granite boulder, used to tie small boats up.

The construction details were simple. The ring was loose, being
interlinked with the eye of a forged eyebolt. The other end of the
eyebolt was split, and the entire assembly was galvanized.

A deep hole was drilled into the granite bolder, a foot above the
high-water mark. An iron wedge was pushed into the split end, and the
eyebolt was inserted into the drilled hole, and hammered home with a
sledge, so the wedge forced the split end to expand until it clinched
against the sides of the drilled hole. This mechanically fixed the
eyebolt into the rock. (I don't know if they made the hole wider near
the bottom, but I wouldn't put it past the Swedes, if they thought it
useful.) Then the eyebolt was slowly heated with a torch, thus also
heating the nearby rock, until all was very hot, and then molten sulfur
was poured in until no more would go in. A day later, it had all cooled.

The sulfur wetted both rock and iron, and formed a robust waterproof
seal. I was told that this is the traditional method for attaching iron
hardware to stone.

With a piece this size (I recall that the eyebolt rod was about 0.5" in
diameter), thermal mismatch won't make much difference, but for larger
pieces it will matter a lot, and no rigid adhesive will work for long
outdoors, between thermal cycling (and freeze-thaw in cold wet areas).

Joe Gwinn