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WHEN TO USE EPOXY CEMENT
When you need a strong rigid workable (e.g. sandable and/or paintable surface) adhesive, particularly for use on metal or hard plastic, epoxy is usually the best choice. Most epoxies dry with little running or shrinkage, and so are good for filling gaps. The major drawback to epoxies is that they consist of two parts (resin and hardener) which must be mixed in small batches, and then applied with your own applicator (e.g., a toothpick or popsicle stick). Some are packaged in a dual-syringe--but that is not an adequate solution, because the components must still be manually mixed in order harden to maximum strength.

WHEN TO USE JB-WELD
JB-Weld is a very strong epoxy cement. JB-Weld is the cement/glue of choice when joining metal parts or filling holes in metals. Otherwise, ordinary epoxy cement or other types of cements/glues are usually better choices. Some other reviewers have complained that the descriptive name "weld" is inappropriate---to some extent that's true. JB Weld can do some jobs welding can't. Conversely some simple welding jobs like joining two thin metal rods at right angles are difficult with JB Weld.

HOW TO USE JB-WELD
General Principles: Although JB WELD makes an excellent filler---and can even be used to cast small parts, it is not remotely as strong as real metal used this way. Whenever possible, use JB WELD as an adhesive---a very thin layer of JB WELD holding two pieces of metal together. Always reinforce with metal pieces when possible. For example, rather than building up a massive flange with JB Weld, you might be able to use scrap peice of metal to form most of the flange, held in place with JB Weld. The greater the relative surface area of contact, the strong the bond will be.

Surface Preparation: As with any adhesive, the surface must be clean and rough. Clean with a solvent (according to another reviewer, acetone is the best solvent for this purpose, but rubbing alcohol will work), roughen the surface, then clean with the solvent again. Use a clean cloth for each application of solvent. I generally use a small grinding wheel in a Dremel tool to roughen the surfaces. You can also scratch the surface with a knife, or use coarse sandpaper, or both depending on the material.

The solvent cleaning is for removing the LAST TRACES of oil from CLEAN surfaces. If the parts are oily, even multiple cleanings with solvent may not be enough---you may redeposit oil from your cleaning cloth or as the solvent evaporates on the surface. So, if you can detect any oil on any portion of the part, or if you have any doubt, clean it with a degreaser first. If you do not have a commercial degreaser handy, a paste of laundry detergent and a stiff brush may do the trick. Only when you are certain that there are no traces of oil is it time for the solvent cleaning(s).

Joining Broken Parts: If you are joining broken parts, with a clean but irregular matching surfaces, limit the roughening to scratching with a wire brush or etching with an acid (but be sure to wash off all traces of the acid). Apply a THIN uniform layer of JB WELD, lightly clamp together hard enough to squeeze out any excess. Sometimes a thick rubber band is perfect. Often you can arrange pieces so that the weight of the top piece will hold the joint together until the JB Weld cures. Sometimes you can place a weight (such as a brick) on top to apply gentle pressure. Do not remove the clamp or pressure until the JB Weld has cured completely. After an hour or two, after the glue has set but is still soft, you can cut off any excess with a knife or razor---but if you don't need to cut the excess off, don't. Often you can build-up the surfaces around a break for added strength. Sometimes blue painters tape can be used to help hold pieces together while the glue sets, and/or to make a temporary stand to hold the pieces in the best orientation. ScotchBlue Painter's Tape for Multi-Surfaces 2090-.75A, 3/4 Inches by 60 Yards, 1 Roll

Joining Dissimilar Parts: Minimize any gaps if possible, e.g., by sanding if possible so that the contact as perfect as possible. If you will be filling substantial gaps, sometimes it is helpful to cover openings with blue painters tape to prevent the JB Weld from flowing away and leaving gaps.

Joining Long Thin Parts (rods or sheets): Try to overlap if possible, or reinforce them with a similar overlapping peice of metal glued in place with JB Weld. To join a 1/8" steel rod, to another 1/8" steel rod, forming a "T" (a common and easy welding job, almost impossible with just JB-Weld), cut two 1"-long "L's" from a heavy-paper clip, (or make L's from similar wire), and embed those with JB-Weld on opposite sides of the joint. You can further strenthen the joint by wrapping fine steel wire around the rods holding the "L"s in place---before covering it all with JB-Weld. Be sure to thoroughly clean the rods and wires first (see below). For small parts, or when wire wouldn't work well, unwaxed dental floss is remarkably strong, and can do an excellent job of reinforcing joints (when embeded in JB Weld). Ideally, apply the JB Weld, then wind the floss tightly into the soft JB Weld.

Filling Holes: Don't forget to prepare the surfaces as described above---even if you can only roughen the surfaces with an ice pick or awl. JB Weld shrinks very little as it cures so fill the hole completely. If it is possible to sand the surface when the JB Weld has hardened, then overfill the hole slightly. Since JB Weld flows a little until it sets, the surface should be horizontal. If not horizontal, you can apply the JB Weld and then cover the hole with blue painters tape until the JB Weld sets. Depending on the job, it is often a better strategy to fill the gap as much as possible with a piece (or pieces) of metal embedded in JB Weld that a single mass of pure JB Weld.

Reinforcing a leaking pipe: Work JB Weld into a piece of fiberglass cloth or with a spatula, apply, and then add more JB Weld to any thin spots and to feather out the edges. You may have to apply several layers of the JB Weld-saturated fiberglass cloth. Sometimes wire cloth (window screening) can be used.

Holes in car body panels etc: If you can cover at least one side of the hole with a piece of sheet metal (held in place by JB Weld) that is a good strategy---the combination of pop-rivets and JB Weld often works especially well, even if you ultimately sand the heads of the pop rivets away. TEKTON 6555 Rivet Gun with 40-pc. Rivets

Mixing: Follow the instructions. A paper plate can be a good mixing surface; popsicle sticks are the best mixing tools. Beware that you must use the same amount of resin and hardener, and they MUST be VERY thoroughly mixed. Mix until you are certain that it is completely and thoroughly mixed, and then continue mixing for twice that time. Seriously!!!

Curing: Follow the instructions, but wait longer than recommended: the longer you wait the stronger the bond. A a day or two at 70 or 80 degrees is a reasonable MINIMUM. Note that epoxies do not "dry"--there are no solvents to evaporate, instead a chemical reaction hardens the cement (a plastic resin). Chemical reactions are proportional to temperature (the rule of thumb is that for each 10 degrees, the reaction speed doubles). Using the rule of thumb, if it takes 1 day to cure at 80 degrees, then it takes 16 days to cure at 40 degrees, and that's only to minimally cured. Okay, I know that waiting this long is not practical in many circumstances---you can probably get away with curing for 4 hours at 90 degrees (but don't go much higher than 90 degrees), and "take it easy" for a couple of days.

WHEN TO USE OTHER EPOXIES
For materials other than metal, particularly for rigid plastics, other epoxies are usually better than JB Weld. Some epoxies are clear, or white, or specialized for particular purposes. For example CLEARBOND H-3S Clear Strong Epoxy Adhesive Syringe - .85oz

WHEN TO USE QUICK-EPOXIES
Ordinary (slow) epoxies (whether JB Weld or other epoxies) dry harder than quick epoxies and are generally the best choice. Maximum strength is the whole point of epoxies--if you don't need maximum strength---you probably do not need epoxy. Use quick epoxies when 1) the hardening speed is essential, 2) when the item cannot be supported in the required orientation while the epoxy sets (at least several hours), or 3) when you have to absolutely minimize flowage. Super-glue is often a good alternative in such situations.

WHEN TO USE OTHER CEMENTS OR GLUES
While epoxies are ideal for a few specific uses (primarily when you need a rigid cement for metal or rigid plastic)--there are many situations when other types of glue are better choices. Epoxies are generally NOT recommended for flexible surfaces, such as leather, wood, or flexible plastic, and generally do not adhere well to glass, etc. While epoxies may work with porous surfaces (paper, wood, ceramics, etc.), other adhesives are usually better.

White Glue: For most light-duty indoor household applications which do not have to be waterproof, ordinary household white glue is safe, cleanup is very easy, and in most cases repairs are redo-able if you make a mistake. White glue shrinks a great deal as it dries, and so is not good for filling holes or large gaps. For example: Elmer's All Multipurpose White Glue, 7 5/8 oz. (E379)

Glue Stick: Think of glue sticks as thick white household glue in stick form. Glue sticks are great with paper, but have few other applications.Avery Glue Stic, 0.26 oz, Pack of 6, (98095)

Wood Glue: Carpenters's wood glue is essentially water-proof (when dry) white household glue. It penetrates and strengthens the wood better than any other type of glue. It is safe, and cleanup is easy. If the joint breaks again (because the wood is weak), it can be re-glued. For example: Elmer's E701 Carpenter's Wood Glue 8-Ounce

Goop: Goop will bond virtually any material, including leather, plastics, glass, and metal. The bond is clear, VERY strong, waterproof, and hard but flexible. Since Goop is clear, if a little extra oozes out, it is barely noticeable. I've used Goop to repair ceramic plant pots, water hoses, and shoes; to seal holes in air-mattresses, to close small holes in window screens, as plumbers paste in assembling plumbing parts, to I also use it to seal rust spots on my dishwasher rack--the Goop it also makes a "cushioned" surface that will prevent scratches to dishes. Goop is particular good for repairing damaged electrical cords. Amazing Goop All-Purpose Household Goop, 3.7-Ounce Tube #130012

Silicon Glue: Silicon glue is best for glass, and when you want a truly flexible connection (for example, to absorb vibrations). It is a good alternative for Goop for general household use on glass, plastic, and metal when you do not need the maximum possible strength. It is safer than Goop, and cleanup is easier. Like Goop, silicon glue takes days to reach reasonable strength, weeks to reach maximum strength. For example: GE Silicone II Household Glue, 2.8 oz

Fabric Glue: Beacon Fabri-Tac Permanent Adhesive, 4-Ounce works amazingly well on fabrics, saturating the surfaces enough to provide a very strong bond, but without soaking through. Depending on the application, fabric glue can be better than sewing. It remains very flexible, e.g., it would probably be great on leather or heavy vinyl (e.g., women's handbags, shoes, luggage, etc.)

Super-Glue (Krazy Glue): Super-glue is very strong, rigid, and fast. In many ways it is similar to 2-minute epoxy---except that no mixing is required. Although very hard, super-glue is brittle, and so, is not recommended for flexible objects. Super-glue is hazardous in that it can easily glue fingers (etc.) together. Previously, I used super-glue frequently on objects (e.g., jewelry) when a clear bond was required---however, Goop is better for such applications, safer, and more conveneient. Opened super-glue keeps poorly, even in tighly sealed glass containers---so I recommended packages of multiple very small tubes. BAZIC Super Glue, 3 grams 0.10 ounces, 6 Per Pack

Liquid Nails/Construction Adhesive: When you need to permanently join a large amount of surface, of almost any kind, Construction Adhesive is usually ideal. If you need to join 2 2x4s to make a 4x4 Construction Adhesive is better than nails. Most construction adhesives are slightly flexible, and so can even be used on leather (i.e., to repair a loose shoe sole), etc. Construction adhesive may leave a stain on porous surfaces, and may stain-through thin surfaces. For small projects, Goop is usually a better choice.

Caulking Compound: You can think of caulking compound as white household glue with alot of inert filler--to use when you need to fill holes. As an adhesive, it is the weakest on this list, but is strong enough for many purposes when spread over a large surface, such as the back of a ceramic tile. A few years ago, I made a brick column to support a mailbox. Traditionally, I should have used mortar--which would have been very time consuming. I could have used construction adhesive (albeit any excess that squeezed out would have been ugly)--but caulking compound was quick, cheap, looks good, and was more than adequate for the job.

Hot Glues: In short, if you really need the glue to set quickly, particularly if you've got alot of gluing to do -- consider hot glues. As several commenters have pointed out, there is a whole world of hot glues (which come in the form of glue sticks which are used in glue guns), many of which work better, or are more convenient, than comparable cold glues. In general, the most important attribute of hot glues is that the glue sets very quickly --- in some cases -- within seconds.. Since most hot glues set quickly, it is tempting to apply them too thickly. Even with hot glue, for maximum strength, you should use the smallest amount that does the job, and apply moderate pressure until the glue sets. Unfortunately, I have only limited experience with hot glues, and cannot supply specific suggestions for specific purposes.
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on March 11, 2015
I hate the choices at the big box stores and have had poor results from several name brands. I needed to 'weld' some dissimilar metals so I bought this larger size JB Weld. First, this is not the tiny 1 oz tubes that don't have enough material to glue anything other than costume jewelry. Of course, 10 ozs is more expensive, but it also has a long shelf life so if you are any kind of handyperson, you will likely use it before it expires. (Also, it is not in those silly, useless "injector" tubes that look like syringes. I've tried the injector style tubes and they are a total waste of money IMO. If there is a secret to getting the two parts to come out of the injestor tubes, I haven't mastered it yet or at my age, maybe I just lack the hand strength to compress the injectors. Trying to squeeze a very viscous glue through two tiny openings, is near impossible and I ended up throwing the tubes away.) These two parts come in toothpaste liike tubes and are easy to use, squeeze and estimate equal amounts. Both components are very thick. For best results, mix well, and then keep mixing for at least three minutes! This is not fast drying, so you have several hours of workability, but within 24 hours at room temperature, it feels as hard as metal. Even though the mixed epoxy is pretty thick, it will "run" for several hours so plan accordingly.

Update: 1/16/17 Two years later, my original box and tubes are still going strong, and I haven't had to buy more yet. Very happy with product ... every use I have come up with, it seems to work well. I actually used it to "weld" a metal gate post to a mounting base bracket and two years later, it hasn't failed. One comment: I recently used it to attach a small exterior item in <60 degree weather, and it took over 24 hours to set up. Although I expected slower cure times for cold weather uses, this was a little longer than I anticipated. Moral: Be prepared for very slow cure times for cold temp use. I've also used it to attach my car's rear view mirror to the windshield and it has worked flawlessly (better than Loctite!).
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on October 22, 2017
This product was perfect for my application. I had to attach a metal picture frame wire to the back of a ceramic tile in order to hang the tile on a wall. I used the JB Weld 8265S according to the package directions and it worked very well. Since this product is warranted at a tensile strength of 3960 psi and my tile weighs 8 oz, I think it may have been a bit of overkill. (I estimate that each side of the wire was covered by about 0.5 square inches of the mixture to a depth of about 1/8".) This epoxy is the recommended bonding product for metal to ceramic. I created a small 1/4" diameter loop on each end of the wire to increase the bonding area. It is important to clean the two surfaces with acetone or alcohol to remove all grease. The metal needs to be abraded with a file to create a rough surface. The ceramic was unglazed on the back and therefore was already rough and porous. The two components of the product must be mixed very thoroughly and in 1:1 proportion by volume. It takes 24 hours to get a complete bond.

One note is worth mentioning: the material dries to a dark gray color and is not suitable if aesthetic considerations are important. Since the wire and the epoxy were on the back of the tile, this was not a problem for this application.

There are two very useful websites for finding the right adhesive for various applications. The first one can be found by searching for thistothat adhesive. It makes recommendations based on the two materials to be bonded. Another great resource is a one page Powerpoint presentation on the MIT website, downloadable as a PDF. Find it by searching for MIT D-Lab_Learn-It_Adhesives. Also, JB Weld has very helpful customer support to help you choose among their many products.
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on April 7, 2018
In 2009 I bought the 10 oz. size to fix a couple of holes in my exhaust pipe, well aft of the converter. I wrapped the affected areas with wire and smeared on JB Weld. It stood up to the heat and pulsing pressure, and I got years more of service from that pipe.

Two years ago, rust holes appeared in the deck of my walking mower. I wanted to keep the mower because it worked fine and the deck was strong. At the same time, I was afraid a hole in the deck could result in an eye injury. With EMT shears, I cut suitable pieces from a tin can. I stuck them over the holes with JB Weld. After two years, the repairs look fine.

Last year, I bought an expensive pair of pruners that often failed to cut small stuff completely because of a small gap between the back of the anvil and the back of the mouth. What was the designer thinking!

To keep small stuff from sliding back over the gap, I put a layer of JB Weld about 1mm thick on the back of the mouth. I figured I’d clean it up with a file if it got where it didn’t belong. It stayed where I intended. The pruners worked better. A second layer of JB Weld fixed the problem entirely.

A few months ago, I bought a watch whose stopwatch button, I discovered, was flush with the side of the case. It was hard to feel where it was, and when I pressed it, it might not go down far enough to work. What was the designer thinking!

I figured a dab of JB Weld on top of the button would allow my finger to push it farther, besides making it easier to feel where the button was. If it flowed down around the sides of the button, it might never work again. I decided to risk it.

I used a toothpick to apply a dab to the top of the button and immediately turned the watch so that the button was down. The JB Weld flowed around the button anyway. I thought I’d need a new watch.

In two hours, the JB Weld still on the paper had hardened enough that it wasn’t sticky and didn’t deform under my finger. With a jeweler’s screwdriver 1mm wide, I was able to remove the JB Weld from the well around the button as easily as modeling clay. I doubt that would have worked with another adhesive. The button still works flawlessly.

After nine years, there’s still a lot in the tubes. The black stuff has started to separate, but it still works. I wouldn’t want to be without JB Weld. If I need more someday, I’ll buy smaller tubes. That should make it easier to mix small quantities in equal parts.
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to repair a fountain cement fiber statue my son accidentally fell into and knocked over and broke. One arm had broken into four pieces. Thankfully, it wasn't the arm that held the water outlet, so it was repairable. I've used JB Weld putties for years and when I found this, I knew it was exactly what I needed so I bought two boxes of it. I only needed one box for this repair though.

I applied the epoxy to each piece, one at a time and let each piece cure for a week at a time before adding each subsequent piece. It took forever, but I had to do it on the weekends in-between working. Each piece was held in place by straps until they were set. After all the pieces were epoxied and cured, I sanded it, re-stained it and finished with a sealant. That was 3 years ago and she still looks as good as the day I put her back in service! I've posted pictures of the broken pieces, epoxied pieces and the finished statue and fountain. The last picture was taken today. I cleaned the fountain today, so that's why it's not running, but as you can see, the statue is still in one piece and you can't even see where the repair was done on it. The white spots are where the stain has worn off in the last 3 years.

If you need to repair anything heavy, buy this. Best stuff on the planet for repairs and worth every penny spent on it.
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VINE VOICEon June 16, 2016
I bought a new black granite sink. I put it in, which is a hassle and takes a bit of time. I then noticed that the sink had a very small hole in the back inside which did not go entirely through the sink. It was likely just a bubble in the granite mix that came to the surface and remained unseen until it got to me. The hole was about a quarter of an inch in size. I didn't want to take out the sink and replace it for two reasons: one it is a lot of work and two it seems like such a waste of materials in the environmental sense.
I called the company and they would replace the sink free of charge (not install). I asked them if I fixed the hole in some way if it would void the lifetime warranty. They said "try it" if it doesn't work we will still cover it. That is where the J-B Weld comes in. The black color of the epoxy is almost a perfect match for the black sink. Since I've used the J-B before I know it is strong. I carefully filled the hole. Later I asked my wife if she could find the repair and it took her some time to find it. It has been about a year since the repair and it is still perfect. Unless you knew the repair was there you would not find it.
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on December 5, 2016
This is my favorite epoxy. I've fixed many things with this epoxy over the years all around my house, yard, and workshop. It has never failed to perform wonderfully! The latest thing was a tiki lamp that had a metal support rod come loose at the weld on the main pole. I sanded the end of the support rod and sanded the broken weld spot on the main pole, then applied the J-B Weld. The next day, it was ready for use and seems stronger than the original weld. Then there was the lamp base, and the 10x10 canopy support, and the pool's net skimmer, and the windmill, and many more items...all fixed with J-B Weld!
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on January 12, 2016
Works well as a metal adhesive, especially when compared to something like E6000. For those connections that don't require a weld, it's handy. I use if for metal art projects that include welding.
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on June 24, 2015
I used JB Weld to adhere a pair of copper scuppers to the concrete spill bowls that adorn my swimming pool. This was kind of a difficult bond due to the different materials and the smoothness of the copper sheet. I live in the desert where the temperature range is 18 to 118f and the epoxy is subjected to water, wind and sun. Nevertheless, this stuff is rock solid. The copper is firmly in place and I expect it will be for years to come. Just follow the instructions and allow at least 24 hrs for it cure.
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on December 14, 2017
This is the epoxy Honda calls for when repairing leaks in the block or heads from aluminum porosity. I used it to repair a crack in an oil passage that passed close to the outside of the block. It worked perfectly. It is not the ordinary J-B Weld you see in the store. It is very hard and strong and will withstand 550 degrees F.
The key is to clean the surface completely. Degrease the surface with brake cleaner. You can also use a water-based degreaser. Sand the surface immediately before applying the epoxy. Allow it to cure for at least 24 hours before disturbing the epoxy. Any hint of oil, even from your hands, will wreck the bond.
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