Glueing magnets to preforms

February 15, 2015

Folks: I like hiding preforms that I glue magnets onto. I have been using hot glue to attach the magnets to the preforms, but after a few months the magnets either come unstuck with the glue remaining affixed to the preforms or the glue detaches from the preform entirely. I have hidden caches of this type of construction in Florida and New Hampshire with the same effect. Is there a better type of glue to use that would withstand high heat (Florida) and extreme cold (New Hampshire)? I think the preforms are made of polypropylene plastic or polyethylene plastic, but not sure. I also experienced the same effect with thus glue on bison tubes.

Edited February 15, 2015 by ducttaperocks

8.6k · February 15, 2015

Expansion/contraction of differing materials is your (well... hot glue's) problem.

Gorilla glue is about as good as it gets.

Clear silicon (in the tub caulk aisle... any hardware store) is not removable under any conditions from any material, once set. Set time is long. It does not affect any plastic(s).

1k · February 15, 2015

I recommend using duct or electrical tape for the magnets in addition to glue. The tape will deteriorate over time, too, but maybe not as fast. Plastics are pretty hard to glue to in the first place, plus you have three dissimilar materials (plastic, metal and the glue) that will expand and contract at different rates with temperature changes. Here in northern IL we have over 110 degree differences between winter and summer. What might be a perfectly good solution in one part of the country might not work so well in another. Most of the caches I find here have the magnets glued and then with duct or electrical tape over that.

19k · February 15, 2015

Heat-shrink tubing would work beautifully if you can find some big enough to go over the preform.

Can the magnet be *inside* of the preform?

February 15, 2015

I've had good luck attaching magnets to preforms with two different methods. Aluminum foil duct tape (not the cloth-backed kind), usually found in the ductwork section of the HVAC aisle at most large hardware stores works well. Just be sure to wrap the tape all the way around the preform so it sticks to itself.

The other method is to use J-B Weld's "PlasticWeld". Scuff the preform first, clean the magnet(s), apply the epoxy and it's done.

11.6k · February 15, 2015

Is there a better type of glue

Hot glue is for indoor craft projects. It tends to lose all its "glue" properties outdoors. There's better glue, and pretty much any "glue" designed to be used outdoors may hold for at least a little while. But if you want to avoid frequent maintenance, a mechanical attachment is best, as mentioned. You've seen how even the best glue seems to only hold the magnet or the tube, or the glue itself breaks after a while. There are magnetic latches that attach with screws. There's a magnet and washer set, and you attach either the magnet or washer (depending on the situation) to the cap or side of the container, and seal any holes with "glue".

There are special industrial adhesives. I've tried Scotch-Weld High Performance Industrial Plastic Adhesive 4694H, which is designed to hold PPE and slick PPV plastic. This kind of stuff is not a craft glue. Use it in well-ventilated areas, follow the directions, and allow it to cure (couple of weeks). It's serious stuff. But I still won't use it as the main support for my magnet on a cache tube. It seems that "glue" isn't always the best way to attach everything. :anibad:

Edited February 15, 2015 by kunarion

11.6k · February 15, 2015

Clear silicon (in the tub caulk aisle... any hardware store) is not removable under any conditions from any material, once set. Set time is long. It does not affect any plastic(s).

I've done a lot of tests with 3M Marine Adhesive Sealant 5200 (an industrial adhesive), and it's amazing on PPV plastics (Lock & Locks). Don't "rough up" the plastic, it sticks best to the cleaned slick surface. It takes weeks to cure, and is as runny as heavy cream. Commercial RTV varies, some works better than others, some is designed to be removable (a specific proven type by brand may be helpful here). And it should be applied rather thick, which requires a long cure time. And you have to use it all soon, since once opened, it cures inside its tube.

The item you're trying to attach may pop right off (magnet or whatever), but not the sealant attached to the container. I don't use preforms, since I still have hundreds of 50ML centrifuge tubes. I've had some success with a thin layer of "super glue" over "super glue primer", which creates a spot for other "better glue" to adhere, But typically, I use wire wrapped around the tube, or some other attachment method. Not glue.

But it's fickle :anicute: . It doesn't stick to the centrifuge tube caps (which are a similar soft plastic as preform soda bottle caps), and doesn't hold "rubber ducky" style plastic. I tried gluing toy animals to the caps and ended up with a cap, toy, and a separate disc of white sealant :laughing: . It came apart clean.

You may attach an item with "better glue", give it a slight tug, and assume it's good to go. But Cachers tend to manhandle the containers, and it's especially problematic if the item is on the cap. You'll get a vague note about the container now being on the ground, fifty finds after the magnet broke off.

Edited February 15, 2015 by kunarion

11.6k · February 15, 2015

I recommend using duct or electrical tape for the magnets in addition to glue. The tape will deteriorate over time, too, but maybe not as fast.

That might do. I also like the aluminum HVAC tape suggestion, and the heat shrink tape suggestion. The "better glue" (such as JB Weld) is great until force is placed in just the wrong place, and leverage pops it off. The extra reinforcement will help everything stay in place.

If bolting the magnets seems OK (using the cabinet-style magnetic latches, for example), the OP may consider attaching the magnet or washer to a strip of Velcro and wrapping the container with it. That way, the container is simple to replace if needed. My most recent cache is a match tube in a slightly larger tube which is secured by Velcro wrapped to a tree branch. Some decorations were glued to the cache container using Goop glue. Goop-style craft glue is in no way a structural adhesive, but it's not for holding my cache up.

Edited February 15, 2015 by kunarion

February 15, 2015

Wow! Thanks to everyone for the extremely informative posts. I will try some of the methods suggested by you guys. It is clear that my "hot glue" is not going to cut it. The suggestion of using Gorilla, etc., glue to affix the magnet, and ALSO using duct tape sounds like a good place to start. I think I need to purchase some stronger magnets to compensate for the tape. Any recommendations on where to get stronger force magnets? About 1 to 2 inches long and about the shape and diameter of a No. 2 pencil? Again, I very much appreciate all the help.

19k · February 15, 2015

Home Depot now carries rare earth supermagnets, as does Michael's craft stores

7.7k · February 15, 2015

Any recommendations on where to get stronger force magnets? About 1 to 2 inches long and about the shape and diameter of a No. 2 pencil?

If you intend to strap this lengthwise along the preform, bear in mind that most cylindrical shaped magnets are magnetized through, meaning your N and S poles are on the smaller, flat round surfaces. If you want the long side of the cylinder to be the strongest, look for diametrically magnetized ones. They are more expensive, though.

A 3/8" x 1" would actually be very strong, I'm not sure you want it that strong - it places unnecessary stress on the duct tape / adhesive.

I bought from magnet4less.com / Applied Magnetics some years ago. No complains. I haven't bought from them since as I think I now have enough magnets to last me a couple of decades.

Edited February 15, 2015 by Chrysalides

3.6k · February 16, 2015

Home Depot now carries rare earth supermagnets, as does Michael's craft stores

Woodcraft store too.

1.5k · February 16, 2015

A bit out of your area, but they ship. And with the current dollar difference you should get some good deals..They have a lot of different shapes/styles.

Lee Valley Tools

11.6k · February 16, 2015

I'm not sure you want it that strong - it places unnecessary stress on the duct tape / adhesive.

I loves me some rare-earth magnets! Part of the fun is designing the system to fit the hide. Magnet on the branch, metal washer on the tube? Magnets on both? Sometimes, I return to one of my magnet caches to change the whole design. One cache I found (not mine) had a magnet, but was at the bottom inside the iron pipe of a chain-link fence -- that one probably should have had a metal washer instead. :anicute:

Edited February 16, 2015 by kunarion

2.6k · February 16, 2015

Heat-shrink tubing would work beautifully if you can find some big enough to go over the preform.

Can the magnet be *inside* of the preform?

I've seen some pretty big shrink tube at Interstate batteries where I buy smaller tubing for 2 gauge welding cable for my golf carts I'd check online for it.

7.7k · February 16, 2015

Heat-shrink tubing would work beautifully if you can find some big enough to go over the preform.

Can the magnet be *inside* of the preform?

I've seen some pretty big shrink tube at Interstate batteries where I buy smaller tubing for 2 gauge welding cable for my golf carts I'd check online for it.

I've used heat shrink tubing on bison tubes but not preforms. Will the heat affect the preform plastic? I'm guessing not, but best be quick with the heat gun (or lighter).

2.6k · February 17, 2015

Heat-shrink tubing would work beautifully if you can find some big enough to go over the preform.

Can the magnet be *inside* of the preform?

I've seen some pretty big shrink tube at Interstate batteries where I buy smaller tubing for 2 gauge welding cable for my golf carts I'd check online for it.

I've used heat shrink tubing on bison tubes but not preforms. Will the heat affect the preform plastic? I'm guessing not, but best be quick with the heat gun (or lighter).

the shrink tubing I use has a sealant inside so it takes a little more heat

I've seen some on line that look like a thin plastic which would probably work fine.

I use a Harbor freight heat gun it has a hi and low setting

7.7k · February 17, 2015

I use a Harbor freight heat gun it has a hi and low setting

I bought a Harbor Freight heat gun some time ago (told my wife I'm "packing heat" when I put it inside the car - she wasn't amused). Third time I used it, it started smoking. It did work remarkably well on heat shrink tubing the first 2 times, I admit.

2.8k · February 17, 2015

The other method is to use J-B Weld's "PlasticWeld". Scuff the preform first, clean the magnet(s), apply the epoxy and it's done.

My method of choice. Have yet to lose magnets when using the JB Weld (no matter what I attach them to!).

2.6k · February 19, 2015

The other method is to use J-B Weld's "PlasticWeld". Scuff the preform first, clean the magnet(s), apply the epoxy and it's done.

My method of choice. Have yet to lose magnets when using the JB Weld (no matter what I attach them to!).

+1....J-B is the way to go.

7.7k · February 19, 2015

Question for you guys using J B Weld - which product do you use? PlasticWeld is the two part epoxy in a syringe that you mix and apply, right? They also make kneadable epoxy putty and lots and lots of other products.

2.6k · February 19, 2015

Question for you guys using J B Weld - which product do you use? PlasticWeld is the two part epoxy in a syringe that you mix and apply, right? They also make kneadable epoxy putty and lots and lots of other products.

I use the old time package with the two toothpaste type tubes....mix an equal amount & apply. I've attached all sorts of magnets to all sorts of containers.

2.8k · February 20, 2015

Question for you guys using J B Weld - which product do you use? PlasticWeld is the two part epoxy in a syringe that you mix and apply, right? They also make kneadable epoxy putty and lots and lots of other products.

I use the old time package with the two toothpaste type tubes....mix an equal amount & apply. I've attached all sorts of magnets to all sorts of containers.

What he said.

http://www.jbweld.com/product/j-b-weld/ or http://www.jbweld.com/product/j-b-kwikweld-3/

I don't think the clear epoxy is as good/strong.

19k · February 20, 2015

Question for you guys using J B Weld - which product do you use? PlasticWeld is the two part epoxy in a syringe that you mix and apply, right? They also make kneadable epoxy putty and lots and lots of other products.

I use the old time package with the two toothpaste type tubes....mix an equal amount & apply. I've attached all sorts of magnets to all sorts of containers.

Isn't JB Weld just another epoxy? I suppose there are all sorts of trade-offs that can be made in the manufacture of epoxy (for instance, the quick set formulas are not as strong).

Personally, I try to never use any adhesive as the primary method of attachment, just as a furniture maker would never rely purely on glue for a wood joint. A mechanical connection is your ace in the hole. The adhesive is just for backup and to hold that mechanical connection together if necessary. An example would be to attach the magnet to the preform with, say, nylon zip ties, then cover that with epoxy so that the zip ties don't slip out of place.

2.6k · February 20, 2015

Not a preform but a wallyworld orange match holder used enough epoxy to cover the magnet and partially wrap around the container. It lasted over 4 years until it was stolen

19k · February 20, 2015

Not a preform but a wallyworld orange match holder used enough epoxy to cover the magnet and partially wrap around the container. It lasted over 4 years until it was stolen

How much temperature variation do you get in your part of California?

2.8k · February 20, 2015

Question for you guys using J B Weld - which product do you use? PlasticWeld is the two part epoxy in a syringe that you mix and apply, right? They also make kneadable epoxy putty and lots and lots of other products.

I use the old time package with the two toothpaste type tubes....mix an equal amount & apply. I've attached all sorts of magnets to all sorts of containers.

Isn't JB Weld just another epoxy? I suppose there are all sorts of trade-offs that can be made in the manufacture of epoxy (for instance, the quick set formulas are not as strong).

Personally, I try to never use any adhesive as the primary method of attachment, just as a furniture maker would never rely purely on glue for a wood joint. A mechanical connection is your ace in the hole. The adhesive is just for backup and to hold that mechanical connection together if necessary. An example would be to attach the magnet to the preform with, say, nylon zip ties, then cover that with epoxy so that the zip ties don't slip out of place.

Yes, it is another epoxy - but a dadgum good one. I have not had a single epoxied magnet failure, and I am here in weather fluctuating New England.

2.6k · February 20, 2015

Not a preform but a wallyworld orange match holder used enough epoxy to cover the magnet and partially wrap around the container. It lasted over 4 years until it was stolen

How much temperature variation do you get in your part of California?

Highs over 100,this January we had snow on the ground prob in the mid to high 20s,average winter lows anywhere from low 40s to below freezing, El. is about 1300ft

Edited February 20, 2015 by vagabond

2.6k · February 23, 2015

Question for you guys using J B Weld - which product do you use? PlasticWeld is the two part epoxy in a syringe that you mix and apply, right? They also make kneadable epoxy putty and lots and lots of other products.

I use the old time package with the two toothpaste type tubes....mix an equal amount & apply. I've attached all sorts of magnets to all sorts of containers.

Isn't JB Weld just another epoxy? I suppose there are all sorts of trade-offs that can be made in the manufacture of epoxy (for instance, the quick set formulas are not as strong).

Personally, I try to never use any adhesive as the primary method of attachment, just as a furniture maker would never rely purely on glue for a wood joint. A mechanical connection is your ace in the hole. The adhesive is just for backup and to hold that mechanical connection together if necessary. An example would be to attach the magnet to the preform with, say, nylon zip ties, then cover that with epoxy so that the zip ties don't slip out of place.

Yes, it is another epoxy - but a dadgum good one. I have not had a single epoxied magnet failure, and I am here in weather fluctuating New England.

Agreed.......I've used a lot of epoxy's over the years and some just don't harden properly every time.

Now I ONLY use J-B.

February 23, 2015

Also sand the plastic with a very coarse sandpaper. This gives the glue a better surface to hold onto.

1.4k · February 23, 2015

When I use magnets on preforms I have always gone with earth magnets with duct tape over them. They have always seemed to work out just fine. I have also found that hose clamps fit over the preforms well and I have clamped on zip ties. Then zip tied them to stuff.

If you were really worried you could probably use a hose clamp at the top and bottom of the preform and maybe a piece of wood strip between and then get the magnets that you can screw on. That would never fail but probably over kill for the hide.

3.1k · February 25, 2015

Also sand the plastic with a very coarse sandpaper. This gives the glue a better surface to hold onto.

This is a solid tip! Otherwise, I've seen the magnets just come off after repeated finds. Just like in climbing, redundancy will help keep equipment failure from ruining your day

February 25, 2015

When using any container that is "tube" shaped I glue the magnet, then use shrink tube over that...this works very well for me.

19k · February 27, 2015

When I use magnets on preforms I have always gone with earth magnets with duct tape over them. They have always seemed to work out just fine.

I have seen that method fail quite rapidly. The hammering effect at the edges of the rare-earth magnets ( pet peeve... they are "rare-earth", not "earth") from people replacing the cache wears away the duct tape, and soon the magnet is sticking to the metal, not the cache.

6.1k · February 27, 2015

Question for you guys using J B Weld - which product do you use? PlasticWeld is the two part epoxy in a syringe that you mix and apply, right? They also make kneadable epoxy putty and lots and lots of other products.

I use the old time package with the two toothpaste type tubes....mix an equal amount & apply. I've attached all sorts of magnets to all sorts of containers.

Isn't JB Weld just another epoxy? I suppose there are all sorts of trade-offs that can be made in the manufacture of epoxy (for instance, the quick set formulas are not as strong).

Personally, I try to never use any adhesive as the primary method of attachment, just as a furniture maker would never rely purely on glue for a wood joint. A mechanical connection is your ace in the hole. The adhesive is just for backup and to hold that mechanical connection together if necessary. An example would be to attach the magnet to the preform with, say, nylon zip ties, then cover that with epoxy so that the zip ties don't slip out of place.

Yes, it is another epoxy - but a dadgum good one. I have not had a single epoxied magnet failure, and I am here in weather fluctuating New England.

Agreed.......I've used a lot of epoxy's over the years and some just don't harden properly every time.

Now I ONLY use J-B.

JB weld often breaks loose from plastic, from what I've noticed, although it dries rather solid. I'd prefer to buy the magnets with holes in them and bolt them to the container with JB weld acting as a gasket/sealer.

15.3k · February 27, 2015

JB weld often breaks loose from plastic, from what I've noticed, although it dries rather solid. I'd prefer to buy the magnets with holes in them and bolt them to the container with JB weld acting as a gasket/sealer.

I've become a fan of using mechanical fasteners (bolts, rivets, whatever), and then using an adhesive as a sealant.

But with that said, I've had pretty good luck with JB Weld, even repairing car parts with it (which then survived regular use for years until I sold the car). I would expect that a layer of JB Weld going all the way around the preform would bear a strong resemblance to a mechanical fastener.

6.1k · February 27, 2015

JB weld often breaks loose from plastic, from what I've noticed, although it dries rather solid. I'd prefer to buy the magnets with holes in them and bolt them to the container with JB weld acting as a gasket/sealer.
I've become a fan of using mechanical fasteners (bolts, rivets, whatever), and then using an adhesive as a sealant.

But with that said, I've had pretty good luck with JB Weld, even repairing car parts with it (which then survived regular use for years until I sold the car). I would expect that a layer of JB Weld going all the way around the preform would bear a strong resemblance to a mechanical fastener.

It doesn't seem to adhere to the plastic on lock n locks, even if roughened up. It comes off of the outside of kayaks also, although I've found that if used on the inside of the hole, while melting the original plastic to the outside, works fine. It's a solid material, but often doesn't adhere to plastic well.

2.6k · February 27, 2015

JB weld often breaks loose from plastic, from what I've noticed, although it dries rather solid. I'd prefer to buy the magnets with holes in them and bolt them to the container with JB weld acting as a gasket/sealer.
I've become a fan of using mechanical fasteners (bolts, rivets, whatever), and then using an adhesive as a sealant.

But with that said, I've had pretty good luck with JB Weld, even repairing car parts with it (which then survived regular use for years until I sold the car). I would expect that a layer of JB Weld going all the way around the preform would bear a strong resemblance to a mechanical fastener.

+1 or at least over half way

March 1, 2015

I have been indtroduced to a "tape" that when stretched and looped over itself makes one magnificent bond. I bought mine at ACE hardware and at Harbor Freight. I is not sticky and looks like electrical tape. The roll comes with an interface of clear plastic between the layers of the roll. You just need to unroll and remove the clear plastic layer, stretch the black tape and wrap. It is pretty amazing.

March 1, 2015

keepin' it simple- best buy 2 years ago, Gorilla Glue Black Duct Tape roll is in my caching bag 365 & used a zillion times to do magnets or repair my (and others') caches... :wub:

2.6k · March 1, 2015

I have been indtroduced to a "tape" that when stretched and looped over itself makes one magnificent bond. I bought mine at ACE hardware and at Harbor Freight. I is not sticky and looks like electrical tape. The roll comes with an interface of clear plastic between the layers of the roll. You just need to unroll and remove the clear plastic layer, stretch the black tape and wrap. It is pretty amazing.

it comes in different colors I have it in red blue and yellow, it will also hold up under light pressure like a temp fix for a radiator hose

19k · March 1, 2015

I have been indtroduced to a "tape" that when stretched and looped over itself makes one magnificent bond. I bought mine at ACE hardware and at Harbor Freight. I is not sticky and looks like electrical tape. The roll comes with an interface of clear plastic between the layers of the roll. You just need to unroll and remove the clear plastic layer, stretch the black tape and wrap. It is pretty amazing.

I think I know the stuff you're talking about. Saw it at Home Depot. I think they show it being used (among other things) to repair a leaky pipe. That works well, huh?

I think this is what I'm thinking of

Lowe's: http://www.lowes.com/pd_26668-66601-86001_0__?productId=1076397

Edited March 1, 2015 by knowschad

7.7k · March 2, 2015

There's another type I came across (but have not used). Sold under the name "Fiber Fix" and maybe others. Sounds like a diet supplement for regularity, but it's tape that's activated by water, then hardens. One small problem with this one is that once the packaging is opened, you need to use all of it.

3.7k · March 2, 2015

Something else that nobody seems to have mentioned...sanding the surface of the preform before applying adhesive is also recommended. Glue will naturally have a harder time adhering to smooth surfaces, but will form a much better bond to a rough surface.

March 2, 2015

Has anyone tried Shoe Goo?

7.7k · March 2, 2015

Something else that nobody seems to have mentioned...sanding the surface of the preform before applying adhesive is also recommended. Glue will naturally have a harder time adhering to smooth surfaces, but will form a much better bond to a rough surface.

The Seagnoid mentioned it in #30. Kunarion said NOT to do it when using 3M Marine Adhesive Sealant 5200.

19k · March 2, 2015

Has anyone tried Shoe Goo?

Same as any other adhesive... it will only assist a mechanical connection.

Glueing magnets to preforms

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