I’m going to make a plaque (for lack of a better term) for our Danish trainer. It will be two smooth “river rocks,” each laser-etched with a word — said rocks about 2.5″ x 2″ or smaller. They will be mounted on a piece of bird’s-eye maple.
My first thought is epoxy. One rock is pretty flat on the back. But the other one doesn’t have much of a flat place. Two ideas I’ve thought of, need feedback, and help on technique:
- Flatten a spot in the back of the un-flat rock (sand? grind?) and epoxy both rocks directly to the wood or………
- Drill 2 or 3 small holes in the backs of the rocks and epoxy in small diameter metal “rod” (if 1/16th is called a rod), and drill corresponding holes in the wood, epoxy there, plus a spot of epoxy on the rock itself. How to drill the holes in the rocks — what kind of bit to use? I can’t guarantee these are actually rocks, as opposed to pseudo-river-rocks, but they look like they probably are.
Originally, I was going to make depressions in the wood to nest the rocks in, but that might be kinda risky. There is a spalted crack lengthwise near where one of the rocks will rest, don’t want to cause any problems with that. It’s part of the “message”.
I cannot break these! Need to have it all done in a couple weeks, and have no idea where I could get these particular inscribed rocks again. I picked ’em out of a basket while shopping out of town last year.
It’s rare for me to get an even remotely artistic idea, so help me out here, lead me to fulfillment, LOL!
forestgirl — you can take the girl out of the forest, but you can’t take the forest out of the girl 😉
Replies
Essentially you cannot risk either the rocks or the wood.
I would be very wary of taking a tool to the rocks. if you put pressure on a flaw it will split the rock. Vibration may also cause a crack. The risks would be less if you knew exactly what the rocks were.
Have you considered "building up" a small patch behind the unflat rock?. Either make a small, thin wooden disc, cut out the centre and then epoxy the disc to the wood and the stone to both in one operation or make a little ring out of a flexible plastic, wax it well and use it to create a little well into which you can pour a little thick epoxy, place the rock and remove the ring when the epoxy starts to gel.
Sounds a fun project, pity about the irreplacibility of the components.
1. You can flatten a small portion safely by holding the rock against a belt sander.
2. Polyurethane builders' adhesive will hold them perfectly well.
David Ring
http://www.touchwood.co.il/?lang=e&id=1
Use the poly adhesive or even silicon seal if you have some around the house. Lacking either one of those, bridge the gap between rock and wood with a dowel..... use 5 minute epoxy to attach rock/dowel/wood.
Since you are being artistic, the attachment is a critical component. At least in my world it is. By attachment I'm not so much referring to the glue, but to the relationship between the rocks to each other and to the wood plaque. You may want to keep both rocks proud of the surface or you may want to revisit your original idea to imbed them into the surface. Some means can be employed to reinforce the spalted crack.... or perhaps not.
I would epoxy a small block of wood to the back of each rock after installing a threaded insert into the oppoosite side of the block. Then, I'd route a short stopped dado into the mounting board that would allow the blocks to inset and allow for wood expansion. A single machine screw into the threaded insert would hold it together, and the block-in-dado would hold the rocks in the intended orientation.
If the plaque will eventually be hung up on a wall, I'd use the best epoxy I could find.
If it will be set on a table (so that the glue doesn't actually need to hold the weight) then I'd use a polyurethane glue. Actually, if you read the labels, most polyurethane glues say that they will adhere to masonry and such.
Hi Forestgirl,
To get a stable attachment you need three contact points, like the legs on a stool. If the back of the rock is convex you should glue three short blocks or dowel lengths to the back, in a triangular pattern, and then sand them down (once the glue is set) on a piece of sandpaper on the bench top, like you were flattening a plane sole, until you have the dowels as short as possible. I would stain the blocks/dowels with a black felt tip marker, before starting, to make them less visible.
Either a polyurethane or an epoxy would work but my first choice would be an epoxy.
Once you have the three legs it will be easy to glue them onto the plaque.
John White
Thanks to all for the suggestions. I'm exhausted tonight, and a bit buzzy with dinner drinks. I have an adhesive I want to ask about, but can't remember the name. Will review all these messages tomorrow and write back with questions.
I'm trying real hard to pretend I'm not too old for this Serious Dressage Riding stuff. Geez, Louise, I'm tired.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
They have thick epoxy pastes in the hardware store. I'm sure you've seen them -- they glue all sorts of stuff to a bottle so it looks like some sort of junk sculpture robot. PC-7 is one brand.
I've used this stuff to successfully clue all sorts of difficult projects. I'm sure it would work in your case. It has the advantage of being thick enough to not sag and run like a normal epoxy glue would tend to do, and it sticks to pretty much anything short of Teflon.
Mike HennessyPittsburgh, PA
Liquid-nails would be an easy choice. You are in a area that ought to have good marine supply sources, so if you want to find something at about five times the cost, you could find it there. Anytime you adhere two objects with different expansion coefficients, it is good to have flexibility between them. Thus, I would not use something that might not flex, if the recipient hung it on the wall over his glass top credenza, only to have the rocks fall off and break the glass top whenever the MC in the wood changed. ha
That's an excellent point, and one that i had not thought about when I posted earlier.One product that is perfect for this is a urethane sealant-style of caulk. They are generally available in the big box stores, usually being sold as a concrete crack filler. Sometimes they are also available in the ceramic tile department, since it can also be used for some shower-pan installs.This stuff is stickier than gorilla glue, does not foam, and cures to be almost like the rubber in a tire.
Politics is the antithesis of problem solving.
I'd scuff the back of the uneven rock with a wire brush & use a thickened epoxy to hold it to the wood, or bondo would probably hold it quite well - go out in the yard, pick up a rock of similar size & experiment with a piece of scrap wood :-)
Hi F.G. My choice would be epoxy thickend with cabosil (as against 3m micro balloons).Cabosil will make the epoxy thick without weakening the joint strength allowing you a build up in the low areas and it not sag.Works well on epoxy but there is no cure for old age!! <g>
Some excellent points above. There is a product called "hard as nails". It is a caulk type material which you apply with a gun. I have used it to seal wall-roof joints (stone wall, concrete roof) and after a year it is still clinging like a leech.The product is made by the Evostik (or Bostik, I can never remember who bought whom) group.
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