JB Weld adhesives reviewed by Jeremy Shantz for use in boat repairs at Boating.Guide.

A Guide To The Materials J-B Weld Works On (With Some Awesome Tips To Help)

If you’re looking for the materials J-B Weld works on, you’re in the right place. J-B Weld is a great cold weld, which comes as a two-part epoxy system offering a long-lasting and robust weld on several surfaces. The J-B weld is mixed in a ratio of 1:1 and molded to the desired shape, just like clay molding. After curing, the weld can be drilled and sanded as required without affecting the effectiveness. Unfortunately, the J-B weld doesn’t work on all surfaces and requires some time to set completely.

J-B Weld epoxy requires 4 to 6 hours to achieve dark grey color, 15 to 24 hours to reach the complete cure, and sets to a stiff bond if left overnight. Furthermore, the weld is ideal for materials including metal, wood, plastic, tile, PVC, ceramic, fiberglass, concrete, etc.

This article is all about J-B weld and its suitable materials. The guide is full of valuable information, so keep reading until the end to grab them all!

Favorable And Unfavorable Situations

Are you thinking about where or where not to use J-B weld epoxy? We’ve got you covered, as this section deals with all such relevant information.

Favorable Environment(s) For J-B Weld

Materials J-B Weld Works on depends on the type of J-B Weld you use.
Choose your J-B Weld type wisely.
  1. This epoxy weld is fit for high-temperature environments. It can withstand a constant temperature of 260 degrees Celsius. Furthermore, it can withstand a maximum temperature of 316 degrees Celsius (but only for up to 10 minutes). However, you might have to refer to the individual product packages for additional temperature information.
  2. It’s resistant to water, petroleum, chemicals (only when hardened), and acid.
  3. J-B weld can resist shocks, vibrations, and extreme temperature fluctuations.
  4. You can use it in a microwave oven, but remember that it only survives microwave radiation exposure but not infrared (heat) radiation.
  5. The weld does not conduct electricity, so you can use it in electrical repair works.
  6. J-B weld has proven to maintain the bond to temperatures as low as -67 degrees Fahrenheit.

Unfavorable Environment(s) For J-B Weld

  1. J-B weld isn’t appropriate on wet surfaces (except for WaterWeld, of course). It does work as a sealant but won’t bond well properly on already wet surfaces.
  2. Smooth surfaces aren’t favorable. You’ll have to roughen the surface with sandpaper to make this welding work.
  3. The high temperature of the automotive exhausts makes it unfeasible to use the weld on them.
  4. Any surface with alcohol or petroleum chemicals is unfit for the J-B weld. You’ll have to clean the surface before applying the epoxy.

Favorable And Unfavorable Materials J-B Weld Works On

Let’s now look at the materials on which J-B weld works and fails. Before proceeding, please remember that although the epoxy will work on some materials, the bond won’t be strong enough compared to other materials. 

In reality, “unfavorable materials” won’t bond with just any J-B weld, and you’ll need a specially designed weld for them. Don’t worry because we’ll cover all such relevant information in this section. Just keep reading!

Suitable & Unsuitable Materials

Favorable MaterialsUnfavorable Materials
WoodFlexible rubber surfaces
Works on fiberglass, but here’s a tiny issue. If you’re applying it on a fiberglass boat, you’ll have to roughen the surface, hindering the boat’s strength. So it is not recommended to use it on a fiberglass boat surface.  Vinyl
Any concrete, including bricks, tiles, ceramic, porcelain, marble, and cement.Canvas
Plastic (some plastic varieties excluded in the next section) and ABSPlastic (polypropylene and polyethylene)
GlassPetroleum chemicals
FabricOily substances (it may or may not bond)
Paper (not much practical)

Please make a note that the weld works on ceramic and glass. Since the weld is non-edible, we strongly suggest not to use it on any utensils, as it can be hazardous to your health.


  1. The epoxy can laminate or perform as an adhesive, plug, filter, sealant, or even electrical insulator.
  2. J-B weld isn’t toxic when wholly cured. Still, it’s not suitable for human consumption.
  3. Before you begin the application, make sure that the surface is spotless (to ensure the best bond). You can use soap and water, acetone, or lacquer thinner to clean the surface.
  4. It can serve as a body filler. For instance, suppose if there’s a hole, you can use this weld to fill the gap, and it’s completely safe.

Steps To Apply The Weld Efficiently

Let’s discuss the steps to apply the J-B weld. Since the task is straightforward, we’ll avoid the details and focus on the main stages.

  1. Prepare the surface. Clean the outer layer (as discussed above) and let it dry completely.
  2. If the surface is smooth, roughen it up with sandpaper. Wipe off any dust.
  3. In a mixing tray, pour the resin and hardener in equal amounts, i.e., 1:1
  4. Mix the chemicals well. For safety, use a disposable piece of plastic or wood to mix the chemicals. Also, avoid close contact with the face, as it’s still toxic at this stage.
  5. If you start feeling the heat from the chemicals, it is an indication that the chemical reaction has begun as it mixes well. Here starts the countdown!
  6. You’ll now have roughly 20 minutes before the mixture becomes thick to turn into putty. Weld at the putty stage is moldable like clay. So if you feel it’s runny, wait for a bit to let it thicken.
  7. Apply the mixture to the surface with the help of the same disposable plastic or wood (matchstick will work too).
  8. Clamp the broken pieces together (if required), or leave them to dry overnight, and Voila!

Essential Information

If the mixture seems runny, DO NOT add more hardener. Instead, let it thicken for a few minutes. The objects fixed with the weld become usable after 4-6 hours of application, but let it dry for around 15 hours for the best results. It’ll fully cure and harden within this timeframe.

However, room temperature above 10 degrees Celsius will shorten these timeframes. Fortunately, after 6 hours of weld application, you can heat the welded area to reduce the curing time. Take a heat lamp or anything similar to that, and place it near the welded area.

Frequently Asked JB Weld Questions (FAQs)

Is J-B Weld stronger than welding?

Although J-B weld offers an incredible bond, it’s still incomparable to the original welding. But since you can’t weld anything other than metal, J-B weld stills stay a top-notch choice to achieve welding-like results.

Can you use J-B Weld on the engine block?

The J-B weld can fill up a crack on the engine block. But the bond will break if the weld has intolerable temperature exposure (discussed above). 

How can I remove the fully cured J-B weld?

Removing a fully cured J-B weld layer will not be an easy task. You can sand it out completely (if feasible). Alternatively, you may heat it above 600 degrees Celsius (if possible) to melt it down. However, both these processes can damage the surface with the J-B Weld.

Is J-B weld toxic?

The weld is toxic in the initial application stages but will become non-toxic once fully cured. However, consumption is NOT ADVISED.

Can you J-B weld on hard plastic?

A J-B weld PlasticWeld that becomes translucent yellow when cured is available. That chemical is perfect for hard plastic, PVC, fiberglass, vinyl, etc.

How long can J-B weld last?

The ideal purpose of the J-B weld is for permanent application. So you can expect it to last for a lifetime.

Which is the strongest J-B weld?

The strongest J-B weld is the “J-B weld original”. This mixture surfaces to compete with torch welding. Since torch welding isn’t possible and feasible at all times, J-B weld original cold weld emerged as a popular substitute.

How can you differentiate types of J-B weld?

There’s a wide variety of J-B welds available in the market, several bases with several bases to differentiate:
Based on the surface application: wood, metal, plastic, automotive, brick, ceramic, cloth, concrete, glass, rubber, rotted lumber, underwater/ wet, fiberglass, aluminum, tile, leather, and vinyl.
Based on the attributes: water-resistant, oil-resistant, low odor, high temperature, paintable, sensor safe, sandable, drillable, dries clear, which includes stir stick and mixing tray, stainable, and mold and mildew resistant.
Based on the cure color: clear, white, dark gray, machine gray, tan, off white, black, gray, red, blue, light tan, copper, and translucent yellow.


We’ve covered the J-B weld application process, favorable and unfavorable materials, and situations by the end of this article. It’s a cold weld chemical and not so tricky to handle. However, the chemical reactions can be harmful (can hospitalize you in the worst-case scenario), ensuring utmost safety. Keep away from the reach of children. 

The package contains all the safety measures, the application process, and other relevant information (and perhaps the tube), so never worry. Our job was to offer relevant information, and it’s your turn to fix those broken pieces. Good Luck!

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