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I have a collection of many small stones and shells of different shapes and sizes picked up from various beaches, and it'd be nice to glue some of them together to make some sort of arty model. But these are unusual materials and I'm not sure what type of glue would work best on them.

What sort of adhesive works best for sticking together stones and shells?

(I'm implicitly assuming the same sort will work for both stones and shells, but if not, I'd be grateful for an answer covering both materials.)

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    It may also depend on what you're glueing these items to. In many cases if this is going to not be outside, or abused, hot melt glue is pretty common. If it needs to be a bit more rugged a 2 part epoxy is always nice. – BrownRedHawk May 23 '16 at 12:31
  • @BrownRedHawk Only gluing them to each other. And I'm thinking more paperweights than anything outdoors. – Rand al'Thor May 23 '16 at 12:33
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    I think a 2 part epoxy would give you the longest life. Hot glue however is more forgiving to work with and to some extent can even be undone/corrected. – BrownRedHawk May 23 '16 at 12:34
  • since the materials are porous, i will say any glue with a body, like elmer's , white glue, any wood glue. basically, anycheap basic glue will do. – Reed May 26 '16 at 0:34
  • @Reed Might not hold long-term as well as some others though. – L.B. Aug 15 '16 at 13:10
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As both material are kind of mineral, I think the same glue should work on both. The surface must be clean, in other words free of grease and dust. Ethanol or isopropanol work usually well. It will glue better on rough surface, so if it fits in your work sand paper the surface before cleaning and applying glue. For the shell, depending on the type, maybe some vinegar can make it rough (acidity will attack the calcium of the shell).

I am gluing small stones on substrate with cyanoacrylate (Superglue). It is a thin glue, so it won't fill the "holes" between the stones but will be almost invisible and should also stick if the contact surface is small. Time for the glue to set is extremely quick.

If you want to glue and fill the hole at the same time, 2 components epoxy such as Araldit should work and some are transparent. Those glues are usually quite "thick" but you can make them thinner by heating them (with a hair dryer for example) but they will also set faster with the heat.

I also had success gluing gravel on substrate using PVC glue (wood glue, or "colle blanche" in French), but I don't think it will do if the contact surface is small.

3

Try car filler.

You mix 2 components to create an epoxy. It's not expensive, easy to handle and sets quickly.

I've just tried it on 2 random pebbles without preparing them and it gave a good result. However, the pink color could be a problem.

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    A common commercial name for this, which is sometimes mistaken as the product name, is Bondo. – Matt Jun 28 '16 at 12:51
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Depending on your intended there are a number of glue type. I used GOOP-II for bonding shells to a heavy textured paper - shell bits & shards stay in one place and seems to last forever. Nice thing is it’s clear.

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I have tried silicon glue as well. Usually masons and plumbers use it for quick fix solutions. Preheating the stones with heat gun also enhances the capability in absorbing the glue and better bonding

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I'm with BrownRedHawk in that 2 part epoxy would be good for this job in a general sense.

It bonds really well to all sorts of materials however there are a number of prerequisites that would hinder good adhesion. You want maximum surface area contact. So the items will need to be cleaned of debris and loose components (like smaller rock fragments or shell shards).

Rocks are going to be contoured and shells have a variety of shapes. Not only that but 2 part epoxy (and many other glues known for strength) need time to cure or set in order to get a sustaining bond. Pressure is required and clamps or weight perform that duty.

So make sure everything is clean and you have a way to put pressure on the glue joint so that it does not move while it is setting. I cannot offer specific advice beyond that since rocks and shells, like I said before, are full of variety.

If you wanted something to go on I would build up walls of books, or other items of similar height, beside the object you're gluing so you would not have to try and balance weight on top.

I always found hot glue, like the ones found in less specialized craft stores, to be temporary when crafting so I usually reserve it to kids crafts. That is my opinion however and I am sure there are varying degrees of quality when it comes to hot glues.

  • There are actually different kinds of hot glues out there, some of them more suited to permanent applications than others. In particular, high-temp glues will often work better in adverse circumstances than low-temp ones. (However, I don't personally know of a hot glue that would work particularly well for rocks and shells, hence comment, not answer.) – Martha Jun 28 '16 at 16:47
  • @Martha I need to get more experience with them. The ones I have used are the cheap ones I see in craft stores. They are fine for some things but I have no exposure to better ones. I reread that part of my answer and it reads very dismissive of hot glue which was not my intention. – Matt Jun 28 '16 at 17:29
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A 'grab' type adhesive intended for construction should work well for this. These are generally very viscous and packaged in caulk gun style cartridges.

There are various different formulations but they have broadly similar properties. Gripfill is a common brand but there are many others.

These has the advantage that they provide immediate adhesion and are reasonably tolerant of 'difficult' surfaces. They also have good gap-filling properties and so work well for regular shapes where you can't get a good flat contact area between the two.

One disadvantage is that being very viscous and sticky they can be a bit messy if you aren't careful. It can help in this respect if you dispense some onto a piece of scrap material (wood, card etc) and use a disposable spatula to apply it with more precision than the cartridge gun allows.

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Would tile glue (the white stuff) work? give a good adhesive background and fill the "gaps".

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    Is this meant to be an answer? If so, can you reword it so it is clear, and maybe add a link to the product you mention. If this is meant to be an additional question, can you please ask it as a new question? – Willeke Nov 26 '17 at 11:26

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