hot glue


Hot Glue (aka Hot Melt Glue, Thermoplastic Adhesive)
This must be one of my favorite materials. It allows you to glue almost anything together in an often easy and semi-durable way. It dries pretty quickly so you don’t have to wait more than a minute or so to proceed with your work. And, even though the most common color is translucent, which dries to a milky white, it comes in many shades.

Hot glue is also great for prototyping when you don’t yet have all the right materials around and you just want to quickly stick two things together, isolate a connection, fill a gap, or even cast a small object.

What is it exactly?
Hot glue is a form of thermoplastic adhesive, i.e. a polymer that is solid at room temperature, turns molten when heated, and bonds as it cools back down. Due to its temperature sensitive nature, hot glue is not suitable for use in extreme temperature environments: it may become very brittle when exposed to low temperatures and begins to soften at temperatures above 70ºC (160ºC). But this also means that it can be remelted and remoulded when needed.

This material is commonly made from combinations of ethylene vinyl acetate, resin, wax, and any assortment of polyamides, polyethylenes, polyester or polypropolenes. It’s usually supplied in solid cylindrical sticks of various diameters and lengths, designed to be melted in an electric glue gun. Most common (household use) stick diameters are 10mm (7/16”) and 7mm (5/16”). Other forms may include pellets, chips, and pillows.

Glue guns heat the glue stick until it melts. The molten glue is then fed through the dispenser by using the trigger (or manually, by pushing the unmelted portion of the glue stick into the melting chamber), and out through the nozzle. Hot glue guns may be low-temperature or high-temperature (high-temperature, low-temperature, and dual-use glue sticks are available in the market). The low-temperature version heats up to around 120ºC (250ºF) and the high-temperature to approximately 195ºC (380ºF), producing a stronger bond. Glue guns also come in a dual version with a switch for both low and high-temperature use.

What for?
Besides gluing things together, hot glue can be used for other purposes, such as:
:: Filling gaps
:: Isolating wire connections when you don’t have, or can’t use, heat shrink tubing
:: Diffusing LEDs
:: Casting material

:: Basics
You’ll need glue sticks and a glue gun. Both can be found on any hardware, arts & crafts, or home improvement store. You can get fancy, but even the most inexpensive glue gun will do the trick.

Insert a glue stick into the back of the glue gun, plug it in, and wait until it gets very hot. Avoid touching the tip of the glue gun, it’ll be hot too, instead test the temperature by squirting out a few blobs of glue onto a piece of paper and checking how well they flow out of the tool. Finally, bring the tip of the gun very close to, but not touching, the surface you want to glue to and pull the trigger :)

When working with a hot glue gun, some kind scrap cardboard should be used to set the tool down. The melted glue will drip from the nozzle, especially when the gun is resting for more than a few seconds. Once it’s unplugged the glue will re-harden inside the melting chamber.

Once the glue stick is no longer visible on the back of the gun another one can be loaded right behind it.

:: Diffusing LEDs

Luminaries – Hot Glue LED Diffusion is a really nice video by Kelsey Meuse showing how to diffuse LEDs with hot glue. See also the instructable Hot Glue LED Diffusion by user depotdevoid.

:: Casting
Images from How to Cast Using Hot Melt Glue, a tutorial by Dead Pepper. And check out the Prop Making – Thermal Adhesives Are Cool! post on Dani’s Mixed Plate for very detailed instructions on how to make your mold, cast with hot glue, and paint the pieces.

Tips & Tricks from the DIY Community
Hot glue can be shaped for a couple seconds before it cools down and dries. While you’re working keep a container with some water close by. As soon as you apply the glue, dip your finger in the water and use it to shape the glue blob. The water will prevent the glue from sticking to or burning your finger.

Watch out for extreme temperature environments or placing hot glued projects near heat or cold sources: it might remelt (heat) or become very brittle (cold).

The fact that the glue remelts when exposed to heat means that, in some instances, you can fix mistakes by reheating it: let your glue gun get very, very hot and touch its tip to the blob of glue you want to remelt.

There is a patent for hot melt adhesive heating by means of microwave, but if you have a microwave and some hot glue sticks laying around…

Interesting links
This to That
a great site with advice for gluing anything to everything.
Precision Hot Glue Gun Instructable
a simple mod to turn a cheap glue gun into a precision instrument.
Hot Melt Adhesive
wikipedia’s definition.

Share your knowledge
If you’d like to contribute content or corrections regarding hot glue, please use the comment form below or add them directly to the openMaterials wiki:
materials/glue/hot glue
tools/hot glue gun

>> about the materials 101 series.

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