Tombac

Key takeaways

Tombac belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tombac to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tombac from memory before moving on to harder problems.

Reference excerpt

Tombac, or tombak, is a brass alloy with high copper content and 5–20% zinc content. Tin, lead or arsenic may be added for colouration. It is a cheap malleable alloy mainly used for medals, ornament, decoration and some munitions. The term may apply to brass alloy with higher zinc content.

Etymology

The term tombak is derived from tembaga, an Indonesian/Malay word of Javanese origin meaning 'copper'. Tembaga entered Dutch usage concurrent with their colonisation of Indonesia. Likely, the term was used generically to describe Indonesian high-copper brass items, including gamelan gongs. It is one of the very few Indonesian loan words used in English or German.

Common types

Andrew Ure, writing in the late 19th century, and summarising with regard to "Tomba[c], or red brass", states that "in the cast state, [it] is an alloy of copper and zinc, containing not more than 20 per cent of the latter constituent." He notes that the specific gravity of brass, in general, is "greater than the mean density of its constituents, varying from 7.82 to 8.73, according to the proportion of zinc and copper". He goes on to note, with regard to tombac in particular—which he uniformly spells as "tombak" (as will thus appear in his quotations)—that its specific gravities are yet higher, with "sheet tombak (81.25 copper + 18.75 zinc) [being] 8.788" and that "tombak wire (87.5 copper + 12.5 zinc) has been found so great as 9.00".

On publishing his A dictionary of the Arts, Manufactures, and Mines in England in 1839, and republishing in the U.S. 1856, Ure noted that,"Red brass, the Tombak of some... consists of more copper and less zinc, than go to the composition of [yellow] brass [at 70 copper, 30 zinc]; [Tombak] being from 2½ to 8 or 10 of the former [copper] to 1 of the latter [zinc]. At the famous brass works of Hegermühl... 11 parts of copper are allowed with 2 of zinc into red brass, from which plates are made that are afterward rolled into sheets. From such an alloy the Dutch foil, as it is called, is manufactured at Nürnberg; Pinchbeek, Similor, Mannheim gold, are merely different names of alloy similar to Prince's metal. The last consists of 3 of copper and 1 of zinc, separately melted, and suddenly incorporated by stirring. A.S. Piggot, writing in 1858, offered a distinct definition of tombac (likewise using the varian "k" spelling), and perhaps drawing from Ure, stated that:Red brass, or tombak, as it is called by some, has a great preponderance of copper, from 5 ounces of zinc down to ¼ ounce of zinc to the pound [of copper]. At Hegermühl, 11 parts of copper are alloyed with 2 of zinc to make a red brass, which is afterward rolled into sheets. At Nürnberg, Dutch foil is made from a similar alloy.Piggot also states separately that the brass used for machinery and locomotives in England was composed of copper 74.5%, zinc 25%, and lead 0.5%, a combination that would make it a tombac according to Ure. Other tombac compositions that Ure reports are:

"tombak for making gilt articles"— Copper 82.0%, zinc 18.0%, lead 1.5%, tin 3.%; Copper 82%, zinc 18%, lead 3%, tin 1%; and Copper 82.3%, zinc 17.5%, tin 0.2%. And "French tombak for sword handles, &c.": copper 80%, zinc 17%, tin 3%; "tombak of the Okar, near Goslar, in the Hartz": copper 80%, zinc 17%, tin 3%; "yellow tombak of Paris for gilt ornaments": copper 85%, zinc 15%, tin a trace percentage; "tombak for [gilt ornaments] from... Hanover": copper 85.3%, zinc 14.7%; a tombak he refers to as "chrysochalk": copper 86%, zinc 14%; "Red tombac from Paris": copper 90.0%, zinc 7.9%, 1.6% lead; and "Red tombac of Vienna": copper 97.8%, zinc 2.2%.

Other alloy formulations include:

"white tombac": ca. 90% copper and 10% zinc, with trace arsenic; and "enamel" or "emailler tombak", suitable for enamelling: ca: 95% copper and 5% zinc.

Ure goes on to report a further composition, with proportions given in the "parts" of each metal—

"Prince's metal": 3 parts copper and 1 part zinc. He then goes on to report further compositions, in "parts", starting from copper and "yellow brass" (the "mean proportion... [of that being] 30 zinc to 70 copper"), rather than presenting fundamental constituents—

"Pinchbeck": "2 parts copper and 1 yellow brass"; and "Mannheim gold (semilor)": 2.8 parts copper, 1.2 parts yellow brass, 0.3 parts tin. Ure goes on to note that the alloy from which a form of "white metal buttons" are cast is composed of 3.2 parts yellow brass, 0.4 parts zinc, 0.2 parts tin.

With regard to modern forms, compositions include:

"CuZn15" (DIN, ISO): UNS, C23000; BS, CW 502L (CZ 102)—tombac with gold colour, good for cold forming, suitable for pressing, hammering, or embossing; "CuZn12": a non-standardized tombac form, with same characteristics and applications as CuZn15, but of slightly different colour; "CuZn10" (DIN, ISO): UNS, C22000; BS, CW 501L (CZ 101)–tombak with similar characteristics and applications as CuZn15 and CuZn12, but with a noticeable reddish colour.

Tempers Typical tempers are soft annealed and rolled hard.

Applications

Tombac is soft and easy to work by hand: hand tools can easily punch, cut, enamel, repousse, engrave, gild, or etch it. It has a higher sheen than most brasses or copper, and does not easily tarnish. Historically, it was used by the Javanese as a faux gold finish for objects d'art and ornaments.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Tombac

Start with the simplest possible case. Write down what Tombac claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tombac before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tombac ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tombac

In research: Tombac appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tombac in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tombac is common in secondary-school and first-year university syllabi. It links to neighbouring topics Coinage metals and alloys, Copper alloys, Zinc alloys, so understanding it makes those chapters shorter.
In everyday life: Look for Tombac outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Tombac in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tombac means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tombac out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tombac in simple terms?

Tombac, or tombak, is a brass alloy with high copper content and 5–20% zinc content. Tin, lead or arsenic may be added for colouration.

Why does Tombac matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tombac?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tombac.