Hot-melt glue

Plain-English definition

Hot-melt glue (hot-melt adhesive) is a solid thermoplastic sold as glue sticks. A glue gun heats the stick until it melts, you squeeze out a bead or fillet, press the parts together, and the bond sets as the glue cools—usually within seconds. There is no mixing and no long cure like epoxy; strength comes from cooling and mechanical “keying” into porous or textured surfaces.

For DIY, hot-melt is the go-to for quick tacks, crafts, fabric, cardboard, and light wood assembly. It is not a structural or high-heat adhesive: joints are bulky, heat-sensitive, and weaker than wood glue, epoxy, or mechanical fixings on load-bearing work.

Why it matters

Glue stick types (what you actually buy)

Most hobby and trade sticks are EVA (ethylene-vinyl acetate) with resins and waxes. Packaging varies by brand, but these are the types you will see on shelves:

Type	Typical melt / gun temp	Best for	Watch out for
General-purpose / “all purpose” EVA	Mid to high (~150–180°C on high-temp guns)	Cardboard, wood, cork, many porous materials	Weak on oily plastics; softens in heat
Low-temperature EVA	~105–130°C	Foam, polystyrene, ribbon, delicate plastics, kids’ crafts	Weaker and more heat-sensitive than high-temp
High-temperature EVA	~160–195°C	Wood, ceramics, heavier cardboard, stronger tack	Will melt or crater foam and thin plastics
Wood / woodworking sticks	Usually high-temp EVA blends	Porous wood, MDF, trim tacking	Still not a substitute for PVA on stressed joints
Flexible / “flex” / crystal-clear	Often low or dual-rated	Fabric, vinyl, uneven surfaces, visible craft bonds	Less rigid; not for stiff structural gaps
Polyamide (“nylon type”)	High-temp industrial guns	Better heat resistance, some metals/ceramics in industry	Uncommon in home craft guns; read gun compatibility
PUR (reactive polyurethane)	Specialist systems	Strong, heat-resistant bonds in professional work	Moisture-sensitive storage; not typical DIY gun sticks

Practical rule: Use the lowest temperature stick that still wets the surface and holds the part. If foam collapses or plastic gloss melts, step down to low-temp sticks or a different adhesive entirely.

Stick diameters — buy what your gun takes

Glue sticks are not interchangeable across diameters. The gun’s feed tube and nozzle are sized for one stick width; the wrong size leaks, jams, or feeds unevenly.

Diameter	Typical gun	Notes
7 mm	Mini / craft guns	~5/16″ in US labeling; good for detail, models, small repairs
11 mm and 12 mm	Standard “full-size” DIY guns	Effectively the same family of stick. US “7/16″” ≈ 11.1 mm; European packs often say 12 mm while US packs say 11 mm or 7/16″. Real diameters vary slightly by brand (roughly ~11–12.3 mm); either label usually fits the same gun if it is not worn oversized.
15 mm	Industrial / high-output guns	For edging, packaging lines, heavy bead work — needs a matching gun

Buying advice: Read the sticker on the gun (7 mm, 11 mm, 12 mm, or 7/16″). Buy sticks in that size only. Do not trim oversized sticks or force undersized ones — you risk melt-back (glue pushing up the stick channel), drips, and poor feed.

Low-temp vs high-temp guns and sticks

• Low-temp (~105–130°C): Safer around heat-sensitive materials; bonds are often weaker and soften sooner in a hot attic or sunny window.
• High-temp (~160–195°C): Stronger, faster wetting on wood and paper; too hot for most foams and many thin plastics.
• Dual-temperature guns: Switch to match the stick and material — do not run high-temp sticks on the low setting unless the label allows it.

Melt temperature on the stick label and the gun setting should agree. Mixing “any stick” in one gun is a common source of poor bonds and damaged workpieces.

Open time, set time, and strength

Hot-melt has a very short open time: once extruded, you have only seconds to a few tens of seconds to position parts before the surface skins and stiffens (exact time depends on bead size, ambient temperature, and stick formula). There is no long “clamp while curing” window like PVA wood glue.

• Handling strength: Often within 30–60 seconds for small joints.
• Full cohesion: Can continue to harden for minutes to hours, but do not expect epoxy-grade gap filling or creep resistance.
• Heat: Bonds soften again near the stick’s heat-distortion temperature (often well below boiling water for standard EVA). Do not use hot-melt where the joint will live in a hot car, above a radiator, or in direct sun on dark surfaces.

What it bonds well — and poorly

Usually works well on:

• Porous materials: wood, paper, cardboard, cork, fabric (with suitable temp)
• Many craft foams — only with low-temp sticks and testing on scrap
• Temporary positioning, wiring tack-downs (not a substitute for proper clips), and template holding

Weak or unreliable on:

• Polyethylene (PE), polypropylene (PP), silicone, and other low-energy plastics
• Oily, dusty, or wet surfaces — glue sits on contamination instead of biting in
• Smooth metals and glass without a mechanical key or a formulation meant for them
• Stressed structural joints, outdoor weathering, or chemical exposure

Light sanding or roughening helps on smooth wood or painted surfaces; clean, dry surfaces always beat more glue.

Safety

• The glue and metal nozzle are hot enough to cause serious burns (high-temp guns especially). Never touch fresh beads; use the stand; unplug to change sticks when possible.
• Ventilate the work area — EVA fumes are usually mild but noticeable; avoid breathing smoke if you overheat or scorch glue.
• Keep guns away from children and pets; a drip on skin sticks while burning — cool under cold water, do not peel.
• Do not use hot-melt for electrical insulation or gas-tight seals unless the product is explicitly rated for that.

Common mistake

The most frequent error is buying the wrong stick diameter or assuming 11 mm and 12 mm are different gun sizes — they are usually the same standard slot, with naming differences from inch vs metric markets. The costly mistake is using high-temp sticks on foam or thin plastic, which melts the substrate while the glue looks fine.

Other typical slip-ups: expecting structural strength from a craft gun; moving parts before the bead has cooled; gluing dirty or glossy plastic without testing; and leaving a hot gun unattended on its side (drips and fire risk). For anything load-bearing, outdoor, or high-temperature, choose wood glue, epoxy, or mechanical fixings instead of hot-melt.