Tool Primer: Understanding Common Glues for #Maker Project
Sooner or later during a Maker project, you have to stick it together. You need glue. Better yet, you need the right glue.
Some glues are formulated to work best porous materials such as paper, wood, or leather. Some are made to work between two different substrates, say plastic and metals. Some are made for smooth, hard materials. Knowing the difference can be the difference between a success and failure in the Home #Makerspace.
Characteristics of Glues
Some important terms & characteristics to understand when working with glue:
Substrate – the materials a user will combine together.
Open Time – how much time a user has before the glue begins to cure and become unworkable.
Cure Time – the amount of time it takes for the glue to become a solid and join two surfaces together.
Bond Strength – how strong the glue sticks two materials together.
Glues with Weak Bonds:
Hot melt adhesive, better known as hot glue, creates a weak but quick-setting bond. Hot glues are my go-to adhesive for kid projects such as the DIY Pinball Arcade Machine, Natural Rock Sculptures and others.
Hot glue comes into two main types: low-temp and high-temp. The temp refers to the glue’s melting point. Low-temp glue is much safer for young children, while high-temp glue is much stronger. Low-temp glue is used in the small, very low cost glue guns. Low-temp sticks come in “mini” size, which are 1/4” round stick about 4” long. High-temp glue guns can range from the $5 to $25 dollar range and fit adult hands. High-temp glue comes in 1/2” sticks about 10” long.
These are the little sticks you may remember from childhood. Glue sticks work on paper and pretty much nothing else. With a long working time, kids can reposition the glue as needed until the project is complete. The “goes on purple and dries clear” types are great for messy children to track their glue usage. They have a cool off-label purpose in 3D printing. Smear a bunch on your print bed, then wait for it to dry. Prints should stick better to the bed.
Rubber cement is simply rubber dissolved in a solvent, such as heptane or acetone. When the quick drying solvent evaporates, it leaves behind a sticky, flexible and repositionable glue surface. This is great for art projects, paper templates, etc. in craft work. Unfortunately, the fumes are a health hazard, so strong ventilation is required. I don’t expose kids to fumes unnecessarily, so I rarely use this type of glue.
Spray glue also works best for paper projects. Light hold spray is great for attaching paper templates, wood template, posters, etc to wide, flat substrates with little or no issues. On the downside, the glue holds unpredictably and the fumes dictate outdoor use only.
Glue With Strong Bonds:
White & Wood Glue:
White tacky glue, regular white glue and wood glue are all PVA (Polyvinyl acetate) glues. PVA glues have an medium to long open working time, about a 24 hour time and a strong bod. They work best on porous surfaces, such as paper and wood. They are not water-proof, but they are extremely cheap.
Super Glue (CA or Cyanoacrylate glue)
To make a strong bond with a non-porous surface, such as some plastics, glass, metal or ceramics, you want CA glue. It is waterproof with a very short open time and curing time. I use CA glue to assemble more technically-minded projects, repair toys (lots of toy repair) and pen-turning. Thick CA glue can be used with wood, but the pores soak up the CA, which uses a lot of material. CA’s biggest drawback is the expensive cost and clean up. If you want to remove CA glue from a joint, you can use acetone (nail polish remover) to clean it. Unfortunately, acetone is a very caustic chemical and repeated exposure carries health risk. Therefore, I rarely design projects to use super glue for the elementary school maker set. Appropriate for middle schoolers.
Similar to rubber cement, contact cement is rubber dissolved in a solvent. The difference is the strength of its bond. Contact cement produces a near-instantaneous bond between two surfaces. Again, while very useful, the smell is atrocious and a health hazard. I don’t use this very often and have very little experience with it.
Polyurethane Glue (Gorilla Glue)
This glue is a newcomer in the world of glues. It bonds many different substrates together, such as plastics, metal, stone, ceramics and wood. It’s tough and water-proof. On the minus side, it is not a gap-filling glue, meaning it only works if the two substrates perfectly mate. Any gap significantly weakens the bond – even weaker than hot glue. The foaming action also means a great deal of squeeze out, although it scraps away easily. More expensive than PVA glue, but cheaper than super glue, reach for this glue to help with outdoor projects.
Long open time, long curing time, high strength. It works on nearly anything, and has excellent gap-filling qualities. Epoxy is a two-part glue which must be mixed to activate it. Once mixed, you have a certain amount of open time, ranging from 5 to 45 minutes. Epoxy can also be used as a finish, such as on bar tops. What’s not to love? The price. At $50 or more per gallon, this is the most expensive glue by a long shot.
An epoxy formulated to bond to metal.
A two-part glue, with a primer and glue. Creates a permanent bond between PVC pipes. I use this extensively when I build soda-bottle water rockets. Degrades in heat, so avoid storing outdoors in a shed. A sheltered garage works better.
Comes in a caulk-gun fitting tube, this adhesive is a great all-around outdoor glue: waterproof, cheap, low-smell, gap filling and strong. It’s a thick, sticky mess of a glue which doesn’t clean easily or well, unless you use acetone or similar solvent. Great for outdoor projects.
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