xkcd.WTF!?

Explanation ➲

Cueball is completing a self-imposed challenge in which he must complete a shopping trip while only buying and using things whose names indicate a material that is not the one used to make it. The items on the list are all anachronyms.

A number of manufactured objects were named for (or at least had names that refer to) their primary materials of construction. With time and advancing technology, it's not uncommon for alternate materials to become available that are one or more of more suitable, less expensive, and/or easier to manufacture, and so the materials of construction change. Names, however, become ingrained in the public consciousness, and can be more difficult to change than a manufacturing process, which leads to the disconnect in this strip: objects that were named for the materials they used to be made of, but are now made of something different.

When these items were originally sold with different materials they may have been seen as "fake". Paper money has also been seen as fake, as its value is written on its face and proposed by a government rather than held in its material such as gold or silver coins.

It should be noted that many of the objects listed on Cueball's shopping list are still sometimes made with the materials that they are named after, they've just been supplanted by alternate materials for the mass market. Silverware can be made of sterling silver, especially in the cutlery of high-end establishments,^{[actual citation needed]} but, unlike steel, traditional pure silver requires regular polishing to retain its finish. Cleaning sponges made of sea sponges are expensive, but can be purchased. Linens made from flax are available; and some people consider it to be the better material, but that's a clear minority of the modern market. Some wood clubs are still made from wood, specifically persimmon. Banknotes of the Japanese yen are still made from wood fiber from E. chrysantha and abaca pulp. Most of the traditional items can be found in antique sales at least occasionally, and some people still use them such as in communities that have separated from modern industry.

Where items named for "iron" are now made with steel or stainless steel, they are still technically made from iron, since steel is an alloy largely consisting of iron as an element (98% or more iron for regular steels, and ~66-75% iron for stainless steel). In common conversation, however, iron is usually used to refer to unalloyed cast or wrought iron, not steel.

Item	Original material	Original still produced and sold in industrial cultures?	Actually made with	Explanation
Tin foil	Tin	Yes	Aluminum	Formerly "tin foil" was made of the metal tin, but aluminum supplanted tin in the early-to-mid 20th century, as aluminum is cheaper and more durable. Foils of all metals are available for industrial and laboratory purposes, but one no longer sees tin foil marketed or sold for common home use, possibly due to health concerns.
Sponges	Sea sponges, i.e., marine invertebrates in the phylum Porifera	Yes	Polyester, polyurethane, cellulose	A sponge is a cleaning aid made of soft, porous material. Typically used for cleaning impervious surfaces, sponges are especially good at absorbing water and water-based solutions. Cleaning sponges made of sea sponges are expensive, but can be purchased.
Silverware	Silver	Yes, though at greater expense than silver-plated or silver-like	Stainless steel	Covers eating utensils, plates and dishes, candlesticks and trophies, which may all these days be electroplated, cupro-nickel alloys or stainless steel. Likely intended to only refer to knives, forks and spoons, which may be found in family heirloom cutlery collections. Silverware can be made of sterling silver, especially in the cutlery of high-end establishments,[actual citation needed] but, unlike steel, traditional pure silver requires regular polishing to retain its finish.
Linens	Flax	Yes	Cotton, hemp, polyester	Linens, also referred to uncountably as linen, are fabric household goods intended for daily use, such as bedding, tablecloths and towels. Linens made from flax are available; and some people consider it to be the better material, but that's a clear minority of the modern market.
Clothes iron	Iron	No	Aluminum, stainless steel & plastics	A device to remove wrinkles in clothing by applying a hot, smooth surface. Early irons were simply flat slabs of iron with handles attached, which had to be manually heated on a stove or fire, or by placing hot coals or similar in a housing on the upward face of the iron. These can be found among antique collections. Modern irons are nearly always electric, and generally use a stainless steel face and plastic housing (which holds the wiring and other components, as well as acting as the handle.)
Ironing board	Wooden board	Yes	Metal, fabric cover	Flat surface for ironing clothes. Wooden boards have largely been supplanted by light but rigid steel sheets with a thin cover of foam and fabric.
Reading glasses	Glass	Yes	Optical plastics	Used to assist farsighted people with focusing on things up close. Glass lenses have typically been replaced by CR-39 plastic due to glass's danger of shattering and higher weight.
9 iron	Iron	Yes	Cast stainless steel, carbon steel	A type of short golf club, normally used for short, lofty approach shots when approaching the green.
3 wood	Wood	Yes	Titanium, carbon fiber	A type of golf club optimized for a long fairway shot off the tee. Some wood clubs are still made from wood, specifically persimmon.
Sidewalk chalk	Calcite chalk	No	Calcium sulfate (gypsum)	Used for making marks on pavement or rocks (e.g., for entertainment, for temporary signs or indicators).
Rubber duck	Rubber	Yes	Vinyl plastics	A rubber duck, or a rubber duckie, is a toy shaped like a duck, that is usually yellow with a flat base. It may be made of rubber or rubber-like material such as vinyl plastic. They are believed to improve developmental skills in children during water play. Also taken advantage of in science, racing and programming.
Paper money (title text)	Paper	Yes, but usually cotton paper	Cotton, linen fibers (U.S. note), polypropylene.	Currency issued by banks in the form of promissory notes. Banknotes of the Japanese yen are still made from wood fiber from E. chrysantha and abaca pulp.