Thread: Coticule Glue Help

This is my first coticule, or natural stone hone at all. I believe it is "old rock". Its 7" x 1.25" and is very thin -- it was glued to a paddle. I believe that it is yellow layer only.

The bottom and edges have hard black glue. I'd like to clean it off, esp the sides, so I can see my stone. Then, I'll re-glue it to a base of some kind.

I've gently scraped off what glue I can, but don't want to damage the stone -- I'd prefer a chemical method.

All the information I've read deals with the glue between the stone and a stone base. So, I don't know if its the same type glue.

Any suggestions?

As thin as it is, I believe that you are asking for trouble if you try to use anything but a good sharp razor blade. I wouldn't use chemicals unless they were water soluble and wipeable. No soaking. That's just my opinion.

What makes you think it's an Old Rock? Without a label it's pretty unlikely you could ID it as such. Your stone was almost certainly originally glued to a slate or BBW base.

Originally Posted by kelbro

As thin as it is, I believe that you are asking for trouble if you try to use anything but a good sharp razor blade. I wouldn't use chemicals unless they were water soluble and wipeable. No soaking. That's just my opinion.

I tried scrubbing with mineral spirits to no avail. When I posted earlier, I was wondering about soaking it in mineral spirits.

Instead, I scrape what I could with a box cutter blade. Then used some sandpaper, which didn't do much, but gave me some slurry. Finally, I used the slurry on a marble slab and ground away what glue I could. Below is the result, which is good enough for regluing.

If you are happy with the above result stop messing with the stone and glue it to a strong base or you'll risk breaking it.

Most Coticules are glued to a piece of slate. Some are glued to a piece of BBW. There are a few rare combo stones that come out of the ground with Coticule juxtaposed to BBW. It seems that your Coticule was glued to a wood backing. Since wood will change dimensions when exposed to water, that will stress the glue bond between the wood and stone.

I agree with Kees that you should forget about cleaning off the existing glue and glue the Coticule to a piece of glass, slate, marble, etc. that will provide a stable base to strengthen it. Otherwise, the thin Coticule is likely to break. There is a reason they have been gluing Coticules to backing stones for well over a century.

I've handled a few old coticules glued to paddles. As long as the paddle is in good shape, there didn't seem to be any real need to remove the stone. As far as I can tell, all the paddles had a form of recess cut into the surface to lodge the stone. Then some sort of tar or pitch was applied applied sparingly on the bottom of the stone (as would seem to be the case here), and completely around the perimeter of the stone, to form a bond with the paddle.

Not that I am necessarily suggesting to do so here, but I am curious about the remark that gluing the stone directly to a wood backing will cause a problem due to wood movement. There are examples of stones that were directly glued to wood backings and do not seem to have suffered the consequences for it. And this is still currently the case with certain Arkansas stones and German slates being sold, as well as the combo Pyrenees/BBW sold by Ardennes-Coticule (see attached picture).

.

it's a shame, you should have stick on a beautiful bbw! you would have contacted it I could have cut you a BBW at the right size. then baking at 180 ° [clean stone without residue of old glue] glued glued natural cooling ....

I've rescued a couple coticule layers myself. I glued them to G10 composite 1/2 inch thick. Almost the same weight as BBW, stable and strong as can be. Can't bear to see a homeless coti layer for cheap on the bay. I removed the left over glue and schist with a delicate touch on a belt sander. YMMV

That probably is old hide glue. If you have cotis like that, the world is your oyster to glue it to something interesting. Just use a good marine epoxy