explain xkcd - User contributions [en]

3194: 16 Part Epoxy

2026-05-18T22:22:02Z

Ello: Slightly changed second line in transcript to include "syringes" and "connected"

{{comic
| number = 3194
| date = January 14, 2026
| title = 16 Part Epoxy
| image = 16_part_epoxy_2x.png
| imagesize = 511x595px
| noexpand = true
| titletext = Some surfaces may seem difficult to glue. But if you research the materials, find tables of what adhesives work on them, and prepare your surfaces carefully, you can fail to glue them in a fun NEW way that fills your house with dangerous vapors.
}}

==Explanation==
This comic refers to {{w|epoxy}} — substances used as adhesives, sealants, and coatings, named for the chemical substructure {{w|epoxide}}, which is the precursor component to these substances turning from liquids to solids.

[[File:FiveMinEpoxy.jpg|thumb|A typical 2-part epoxy applicator.]]Many types of epoxy are multi-part (usually two-part), where the components, such as {{w|resin}} and a {{w|Epoxy#Curing|hardener}}, are stored separately. For ease of use, this can be in parallel syringes (of equal volume, or proportionately different widths to maintain the correct mixing ratio) such that the user squeezes out both of the separate chemicals onto the initial surface, or into a container, by depressing both syringes simultaneously. The user then thoroughly mixes the components, as quickly as possible. The mixture is spread over the surface(s) to be joined or protected, and/or into the gaps to be filled, and if there are separate surfaces involved they are quickly positioned and held in place. The combined epoxy cures quickly, usually within a few minutes. This comic presents a fictitious 16-part epoxy, with the same apparent logic of parallel deposition in mind, with many components that are implausible or make fun of common problems people have when using epoxy in real life.

The title text, as with a couple of the substances involved, references how not all epoxies and glues work on every material, and that applying them on others can also require special techniques or products to gain the best advantage. Some industrial or industrial-grade adhesives contain solvents (e.g. {{w|tetrachloroethylene}}, which is used in E6000 glue) that release harmful vapors as they cure. If used improperly, this can result in the release of chemical vapors in an enclosed space along other dangerous side-effects, while also ''still'' not adhesing as intended.

{| class="wikitable"
|-
!Type
!Real?
!Explanation
|-
|Resin
|{{Yes}}
|A liquid which turns into a polymer when mixed with a hardener.
|-
|Hardener
|{{Yes}}
|A thick liquid which is mixed with resin to create a durable polymer which is commonly used as a glue.
|-
|Filler
|{{Yes}}
|An optional addition to the hardener and resin which changes the properties of the polymer.

Some epoxies are sold as products known as 'fillers', used to repair and cover cracks, holes, and imperfections.
|-
|Softener
|{{Yes}}
|The word is probably being used in humorous contrast to the "hardener" component, and perhaps also by analogy with laundry products that contain a fabric softener alongside a detergent. However, {{w|plasticizer|plasticizers}} are often added to polymers to make them more pliable, and thus to increase their impact resistance. These plasticizers tend to be lost over long periods of time (e.g. by evaporation or degradation), which contributes to old plastic becoming brittle.
|-
|Rosin
|{{Yes}}
|While this looks like a joke entry, this is actually a different kind of resin which is extracted naturally rather than synthesized from other chemicals. Rosin (a kind of '{{w|Flux (metallurgy)|flux}}') is one of two parts that make up rosin-core solder, used in electronic work, where the rosin is located in the center (the "core") of the wire-like solder, similar to how graphite is in the core of a pencil. When heated hot enough to melt, it {{w|Soldering#Flux|cleans corrosion and oxides from the surfaces}} of the metal parts to be joined, creating bare metal surfaces that can be 'wet' by the solder. In rosin-core solder, the two substances are touching rather than kept completely separate, since they're both in solid form, and don't react with each other even when they're heated to melt them. In this respect they differ from common combination epoxy chemicals that will be both liquids that cure together on contact even at room temperature. Rosin is also frequently applied to the bows of string instruments like violins or cellos to improve the sound, as immortalized in the famous song "{{w|The Devil Went Down to Georgia}}" or the folk song {{w|Old Rosin the Beau}}.
|-
|Stuff that bonds permanently to skin and nothing else
|{{No}}
|One key annoyance with sticky substances is the difficulty of removing them when they are inadvertently applied to skin. In hyperbole, we have a substance here that seems to bond *solely* to skin. This may be a reference to {{w|cyanoacrylate|cyanoacrylate adhesives}} ("super glues"), which famously bond quite aggressively to skin (sometimes to positive effect, for medical applications!) due to being moisture-activated, while often failing to bond the target materials. Still, none are known to bond to skin exclusively.{{acn}}
|-
|Stuff that will crack and turn white over a few days, for decorative appearance
|{{Maybe|Not effective as epoxy}}
|Poor finish, where an intended smooth uniform surface cracks or discolors, can be a frustrating problem when applying epoxy mixtures to visible surfaces — especially when the problem only appears some time after you've congratulated yourself on a job well done. This humorously describes this as an intended effect, although there are situations where this truly may be intended. 'Crackle effect' is a real thing for crafters, often created by mixing paint and glue, and an adhesive used to join two pieces or repair a crack or break can be modified for a deliberately cracked or discolored surface to match the other surfaces.
|-
|Placebo
|{{Maybe|Not in the field of adhesives}}
|The {{w|placebo effect}} happens when somebody is told that something has a certain effect, when in reality it has no mechanism of action to produce that effect. This is commonly used in medical studies to determine whether a medication actually does something, as opposed to simply having a {{w|psychosomatic effect}}. Using this term to describe a type of polymer suggests it would make someone believe it is gluing things together without actually doing anything, which is unlikely. Alternatively, this could refer to a component or filler that claims to serve a specific purpose while having no true benefit, merely causing the perception of benefit to the consumer (and presumably causing better reviews).
|-
|Minced duct tape
|{{Maybe|Not intentionally}}
|{{w|Duct tape}} is widely used as a way to join and/or cover things, sometimes in contexts where an epoxy might provide a more high-quality solution. [[Randall]] is pretending that having very small pieces of tape in the mix would add to the epoxy's ability to hold things together. In reality, cutting duct tape into small pieces would weaken it and make it ''less'' effective at sticking things together.
|-
|Acetone fragrance
|{{No}}
|{{w|Acetone}} is a volatile solvent used in a number of glues and paints (including nail polish), but it weakens epoxy and can even be used to remove uncured epoxy. It has a strong, distinctive smell, and is actually toxic, making fragrance an odd reason for adding it to any product. It ''would'' give the epoxy a familiar "chemical smell" that people associate with industrial compounds. The use of 'X fragrance' in an ingredient list, instead of simply listing the ingredient X, usually implies that the actual ingredient is some (cheaper) substitute for X with a similar scent. Since acetone is already inexpensive, perhaps some substitute has been discovered that provides the smell without weakening this glue, though that seems unlikely given the context.
|-
|Powdered bar magnets
|{{Maybe|Yes, but not in resin}}
|This might still work if the pieces could somehow be aligned correctly, as each tiny piece of magnet would still be a magnet in its own right, capable of attracting the other tiny magnets, and thus resisting tension forces. However, it would be much worse than a normal bar magnet, since the magnetic force would be weaker than those that held the original bar together. The micro-magnets would tend to clump together, which might strengthen the glue, but wouldn't help it to bond to surfaces very much unless the surfaces themselves were strongly magnetic.
|-
|Polyethylvinylesteracetate
|{{Maybe|Not in epoxy}}
|This appears to be a reference to {{w|ethylene-vinyl acetate|Poly (ethylene-vinyl acetate)}}, some formulations of which can be used as the adhesive in hot-glue guns. Vinyl acetate is an ester, so the inclusion of that term is redundant. The cadence of the constructed word may also be a reference to the television episode {{w|Lucy Does a TV Commercial}} and its memorable product "Vitameatavegamin". It also resembles the kind of thing often seen in ingredients lists for common household products such as soaps and cleaners, which are fairly meaningless to the average person buying them.
|-
|2-Polyethylvinylesteracetate
|{{Maybe|Unclear}}
|This sounds almost exactly the same as the above item, but {{w|2-Polyprenyl-6-hydroxyphenol methylase|a name with a "2-" prefix}} generally indicates that the initial bit of the name is a {{w|functional group}} attached to the ''second'' position along a chemical chain (often being the carbon-carbon 'spine' of a molecule, in large-molecule organic chemistry), rather than attached to its end. Because the molecule name is (possibly deliberately) malformed, it's hard to tell what is supposed to be attached to the second carbon of what subunit. It may be intended to mimic the confusion consumers have over seemingly-similar named compounds, which may or may not have wildly differing properties.
|-
|Salt and pepper to taste
|{{Maybe|Not for taste, but salt can be useful}}
|Salt and pepper are two incredibly popular seasonings ([[974|not condiments]]) which are used to enhance a dish's flavor, and "salt and pepper to taste" is a phrase found in many food recipes. But the taste of your epoxy should not be your concern. Do not eat epoxy that isn't labelled safe-to-eat. However, salt, sand or other fine grains are sometimes recommended to add a bit of grit to an adhesive. Generally glues or epoxies need the bonded materials to be firmly held together while the glue cures, but when first pressed together, any excess glue is squeezed out and can cause the surfaces to slip around and need to be re-aligned. Any extra friction and spacing in the epoxy can help alleviate that.
|-
|Blood sample from the Gorilla Glue gorillas
|{{No}}{{Citation Needed}}
|{{w|Gorilla Glue}} is a popular brand of superglue which uses {{w|gorillas}} as its mascot. The comic implies that this is because the glue is produced using material taken from a fictional breed of gorillas called “Gorilla Glue” gorillas. Extracting and consuming the blood of a creature or person in an attempt to inherit some of the qualities of the 'donor' is a kind of {{w|sympathetic magic}}, so this may be suggesting that including this will give the epoxy 'the strength of a gorilla', which is commonly considered a powerful animal. Although animal products, including [https://www.sciencedirect.com/topics/engineering/blood-glue blood], have historically been used in some traditional glues, these have typically not come from gorillas, and Gorilla Glue contains no such ingredients.
|-
|Stuff that bonds to every known material except yours
|{{No|Probably not}}
|Another common annoyance when using an adhesive is that each glue type only forms an adhesive bond with certain materials. Poor prior research can cause much frustration when the chosen adhesive does not bond to one or both surfaces intended. In this case, the polymer would bond with every material except for the one you were using, always causing great distress and leaving you in a fix. This is similar to "Stuff that bonds permanently to skin and nothing else" above.
|}

==Transcript==

Standard 16-Part Epoxy

[An epoxy applicator with a single push bar connected to sixteen differently-colored syringes, each labeled]

Resin (coloured beige)

Hardener (mango yellow)

Filler (darker yellow)

Softener (cream)

Rosin (very light red)

Stuff that bonds permanently to skin and nothing else (yellow-dark green)

Stuff that will turn white and crack over a few days, for decorative appearance (light blue)

Placebo (white)

Minced duct tape (grey with a tint of green)

Acetone Fragrance (beige-yellow)

Powdered bar magnets (brown)

Polyethylvinylesteracetate (blue-white)

2-Polyethylvinylesteracetate (blue-white but slightly darker)

Salt and pepper to taste (light grey)

Blood sample from the Gorilla Glue gorillas (red)

Stuff that bonds to every known material except yours (beige)

==Trivia==

The syringe of 'Stuff that will crack and turn white over a few days, for decorative appearance' has light blue fill color on part of the wrong side of the plunger.

{{comic discussion}}<noinclude>

[[Category:Comics with color]]

3114: Building a Fire

2026-05-18T04:27:05Z

Ello: Added "designed" in "Automatic sprinkler systems in buildings are typically designed to be triggered by fire and spray the area with water, wetting any potential fuel and dousing the fire before it spreads."

{{comic
| number = 3114
| date = July 11, 2025
| title = Building a Fire
| image = building_a_fire_2x.png
| imagesize = 671x311px
| noexpand = true
| titletext = That was quicker than usual! The cabin's sprinkler system often makes it really hard to keep anything lit.
}}

==Explanation==
[[Megan]] is demonstrating to [[Cueball]] how to build a campfire. She says she's going to use the {{w|Campfire#Construction_styles|"log cabin" method}}, which is a common [https://www.cabinlife.com/articles/the-5-best-campfire-lays-and-how-to-build-them/ method of laying out fuel for a small fire]. The concept is that sticks (or logs, for larger fires) of wood are placed in layers, with each layer consisting of two sticks placed parallel to one another, with a gap between them. Each subsequent layer is placed perpendicular to the first, so that the sticks bridge the gap in the layer below. This creates an open space in the center in which the tinder, and usually some kindling, is placed and ignited. This method is so named because it vaguely resembles the walls of {{w|log cabins}}, which are also built by placing wooden logs in perpendicular layers to enclose a central space, though on a much larger scale.

At first, Megan's build appears similar to a typical 'log cabin' fire lay. It becomes unusually and unnecessarily detailed when she adds interior walls and miniature furniture in the tiny dwelling, suggesting that she's not just laying out fuel for a fire, but actually going to the trouble of building a miniature log cabin, with all the details and components of a real living space. Things truly take a twist toward the bizarre, however, when she adds plumbing and electrical components to the house. This is not only a complex model, but a structure that apparently includes all the functionality one would expect in a modern dwelling. A fault in the installed wiring then initiates a fire, leading to the promised campfire. Stripped of the complexity, Megan effectively built a campfire which was ignited by electrical heating. Igniting a fire with electricity (either using {{w|electric spark}}s or {{w|Joule_heating|resistive heating}}) is a real method, but not particularly common for campfires. Simulating a common cause of accidental {{w|structure_fire|house fires}}, which are both dangerous and traumatic (tens of thousands of people are killed in house fires every year), is somewhat morbid, which may be the reason Cueball seems so horrified.

The title text continues the joke, in that she usually finds that it needs more time for the fire to ignite, due to also installing a {{w|fire sprinkler system}}. Automatic sprinkler systems in buildings are typically designed to be triggered by fire and spray the area with water, wetting any potential fuel and dousing the fire before it spreads. The level of detail in Megan's cabin is not only wildly unnecessary, it's actively counterproductive to her supposed purpose of starting a fire. This campfire was only started rapidly because the sprinkler system didn't work properly.

Megan says that she is going to build a square cabin, and this may be a reference to [[2891: Log Cabin]], as the log cabin contained a logarithmic spiral, and this square cabin is just a normal cabin.
==Transcript==

:[A tent in a field stands in the background to the left of Cueball, who stands behind Megan, who is kneeling and arranging sticks into the first few layers of a small log cabin.]
:Cueball: Can you show me how to build a campfire?
:Megan: Sure! We'll use the log cabin method.
:Megan: First, we build a square cabin out of sticks.

:[Cueball now stands to the right of frame, opposite Megan with the cabin between them. The cabin has gotten taller and is becoming better defined. Megan holds a tiny table in one hand and tiny chair in the other.]
:Megan: Next, we'll add interior walls, doors, and some cabin furniture made from twigs.
:Cueball: This is very elaborate.

:[The cabin now has a gable roof and an electrical wire leads from the base of the cabin to a coil of wire in Megan's hand and then off panel to the left. Lightning symbols above the wire indicate the wire is energized and perhaps shorting out.]
:Megan: Now we'll add some rudimentary plumbing and electrical wiring. 50 amps, nothing fancy.
:Cueball: It kind of seems like you're just building a cabin.
:Megan: I just —
:Megan: ...oops.

:[The tiny log cabin is engulfed in flames. Cueball is leaning away from the cabin and holding his hand to shield his face from the heat.]
:Megan: I think my wiring wasn't up to code.
:Cueball: ''AAAAA!''
:Megan: ...and that's how you build a fire!

{{comic discussion}}<noinclude>
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]

2024: Light Hacks

2026-05-17T17:50:55Z

Ello: Added explanation of the unlikeliness of the "Distract an advanced civilization and build a smaller dyson sphere inside theirs" prank.

<noinclude>{{distinguish|2875: 2024}}</noinclude>
{{comic
| number = 2024
| date = July 25, 2018
| title = Light Hacks
| image = light_hacks.png
| titletext = Life hack: Wait for an advanced civilization to be briefly distracted, then sneak in and construct a slightly smaller Dyson sphere inside theirs.
}}

==Explanation==
"{{w|Life hack}}ing" is the practice of using common everyday items in novel ways to increase the convenience or enjoyment of daily activities. This comic pokes fun at the many blogs and video channels that purport to cover life hacking tips, but merely point out obvious or intended uses for products or well known techniques as low effort clickbait.

[[Megan]] tells someone off panel that, by using sheets of paper, she can reflect and diffuse the light coming from a lightbulb. She refers to her discovery as a life hack, while the person off-panel sarcastically points out that all she has done is reinvent the lampshade, to which Megan again refers to as a life hack.

A {{w|Dyson sphere}} is a hypothetical energy-collecting megastructure encompassing a star, and collecting a large percent of its energy in the process. It is named after the physicist and mathematician {{w|Freeman Dyson}}.

The joke here is that Dyson spheres are generally not intended for lightbulbs,{{Citation needed}} yet using them in this way is suggested by Megan as a life hack, poking fun at the fact that life hacks make things more complicated instead of convenient. Freeman Dyson argued that Dyson spheres, if they existed, could be found by infrared surveys, as large objects that would emit infrared radiation. [https://www.ikea.com/us/en/p/ikea-ps-2014-pendant-lamp-white-silver-color-00311498/ IKEA pendant lampshades] are spherical shells that surround the bulb. Megan claims studies have tried to use infrared surveys to find Dyson spheres at Ikea locations, without success. When the other person tells her the easier way, searching for it online, she eagerly refers to his method as another life hack, much to the other person's annoyance.

The title text creates a different sort of confusion of the term lifehack, with another sort of popular clickbait videos. Described activity, if done, would be considered a prank - depriving the distractible civilization of their sunlight and energy source, while redirecting the energy to Earth. However, this sort of prank would be extremely hard to pull off as the target civilization would have to be unaware of the smaller dyson sphere for decades if not centuries during which it is built, which Randall ironically calls "briefly distracted".

==Transcript==
:[Megan walks to the right, holding a sheet of paper and a light bulb]
:Megan: I discovered a cool life hack - you can put a white sheet behind a lightbulb to reflect more light.
:Off-panel voice: I'm ... not sure that's a life hack.

:[Megan stops, and positions the light bulb between two sheets of paper]
:Megan: And you can put a sheet in front to diffuse the light.
:Off-panel voice: So you've invented the lampshade.
:Megan: '''''Life hacks!'''''

:Megan: Freeman Dyson suggested that advanced civilizations would build spherical shells that surrounded their bulbs, redirecting 100% of their energy.
:Off-panel voice: Yes, they have those at IKEA.

:Megan: Well, they might. Infrared surveys are inconclusive.
:Off-panel voice: You know you can just check their website.
:Megan: Ooh, great life hack!
:Off-panel voice: ''No!''

{{comic discussion}}

[[Category:Comics featuring Megan]]