Pure Gold and Copper

Question #1: Nickel and Platinum

As far as the laws of tumah and taharah are concerned, what is the halachic status of metals that have been discovered and isolated since the times of Chazal, which include zinc, chromium, manganese, nickel, magnesium, platinum, aluminum, titanium and many others?

Question #2: Pure Gold Bells

In this week’s parsha, the Torah describes the bells that are attached to the robe (me’il) worn by the kohein gadol. These bells were made so that their sound should be heard when the kohein gadol enters the Sanctuary (Shemos 25:35). A bell made of 100% gold will not ring because the metal is too soft. For a gold bell to ring, it must be an alloy including a small percentage of a different metal. So, how can the Torah say in Parshas Pikudei that the bells were made from “zahav tahor,” pure gold?

Question #3:

At the time of the Korach rebellion, when 250 individuals offered incense, the Torah (Bamidbar 16:17-18) does not describe what metal they used for their censers, their coal pans. However, later (Bamidbar 17:4) the Torah tells us that they were made of nechoshes, which usually means “copper,” although I have seen translations that render it “bronze.” Does it make a halachic difference whether they were made from copper or from bronze?

What is the difference between bronze, brass and copper?

Copper is an element, with an atomic number of 29, meaning that every copper atom has 29 protons. Various other metals, such as tin, zinc or nickel, can be added to copper to create alloys with somewhat different properties than pure copper. In our world, one of the primary uses of copper is for electric wiring, since it is an excellent conductor of heat and electricity, and, for this use, pure copper filament is used. However, when using copper in most other applications, other metals are added to the copper, which gives it qualities useful for the desired application.

Both bronze, an alloy of predominantly copper with some tin, and brass, an alloy of copper and zinc, are treated halachically as copper, since the Mishnah implies that an alloy would be treated as its majority constituent (Keilim 11:4). Those who translate the word nechoshes in the context of the coal pans as “bronze” assume that the copper would have been alloyed to increase its strength and heat resistance and to decrease its malleability. Tin, the usual other major component of bronze, is also an element, with the atomic number of 50. Tin has been known since antiquity, and has been used both in relatively pure form and in alloys of bronze for thousands of years. Brass is a naturally occurring alloy of copper and zinc, and has been used for over two thousand years. Only about three hundred years ago was zinc isolated and recognized as a separate metal with an atomic number of 30. Different types of brass vary in the ratio of copper to zinc, and may have other elements, such as arsenic or antimony, added. It is also possible, but rare, that the brass contains more zinc than copper.

Since bronze is predominantly copper and had already been developed and commonly used by the era of Yetzias Mitzrayim, there seems to be nothing wrong with assuming that nechoshes in connection with the mishkan and other references in the Torah means bronze, rather than pure copper. Nevertheless, since we usually translate nechoshes as copper, that is the way I am going to translate it.

At the time of the giving of the Torah, six metals were in common usage: gold, silver, copper, iron, tin and lead (see Bamidbar 31:22). There, the context is kashering used equipment made from these metals before they may be treated as kosher, and Chazal also derive the requirement to immerse food equipment made from these metals that was previously owned by non-Jews (Avodah Zarah 75b).

As we know from the Mishnah and the Gemara (fourth chapter of Bava Metzia), gold, silver and copper have been used as currencies for millennia. Copper, the least valuable of the three, was used for smaller valued coins (think of pennies) whereas silver was used for higher valued coins (think of dimes, quarters and dollars). (I will allow you to imagine which metal is the major component of a nickel.) In the days before paper money and electronic transfers, large transactions required gold coins. This is very different from the contemporary gold coins, which are used as investment and collectors’ items, not as currency. Today, even the coins that were traditionally minted from silver and copper are predominantly composed of base metals of lesser value, so that the coin does not contain the metallic equivalent of its face value. (During the development of modern Europe, governments regularly debased their currencies of gold, silver and copper as an early means of “minting more currency,” with which to meet their military budgets.)

Metals in the Mishkan

The Mishkan and the Beis Hamikdash predominantly required use of the more valuable metals, gold and silver, but copper did have its place. It was used mainly for the kiyor, the laver or sink used by the kohanim to wash their hands and feet prior to performing the avodah, for the base of the wooden walls of the Mishkan, for the sides and utensils of the mizbeiach, the stand of the kiyor, and as hooks, overlay, and trim on various vessels.

Categories of vessels

Prior to addressing our opening questions, I need to explain some principles of tumah and taharah. Whether utensils are susceptible to tumah depends on the material from which they are made; some materials can become tamei and others cannot. Most items made of wood, cloth, earthenware, metal, leather or bone can contract tumah; items made of unfired earth or stone usually cannot.


One of the qualities of metals is that they are fully recyclable. Metal can be melted down to create new items, and there is usually no quality lost by reusing metal rather than using freshly mined material. In this aspect, metal had a unique quality over most materials that were available in the ancient world, such as leather, stone, brick, wood or earthenware, none of which are recyclable in the same way.

There is even a halachic advantage to reprocessing metal. Should a metal utensil become tamei, melting it down or breaking it until it can no longer be used makes the metal tahor, min haTorah, since only utensils are capable of being tamei.

At one point, this led to a concern: There are two ways to remove tumah from a tamei utensil. One is by immersing it in a mikveh or spring, after which we need to wait until nightfall for the utensil to become tahor. (If a utensil became tamei meis by contact with a corpse, a week’s time must transpire within which the utensil must be sprinkled on two different days with spring water containing ashes of the parah adumah, before immersion in a mikveh or spring can render it tahor.)

The second method of making a tamei utensil tahor is by breaking or melting it so that it is no longer serviceable as a utensil, then having a smith repair or manufacture it into a new utensil. Min haTorah, this latter method immediately makes the utensil tahor (i.e., one does not have to wait until nightfall). However, this led to a problem (Shabbos 16b): According to Abayei, the concern was that people may not break the utensil sufficiently. According to Rava, the concern was that people may confuse the laws of tevillah with the laws of breakage and forget that one needs to wait until nightfall after tevillah to use them. Both amora’im agree that there is a concern that people will treat the utensil as tahor when it is still tamei.

To avoid this problem, Chazal established a rule that a metal utensil that was tamei, was broken to make it tahor, and was then manufactured into a new utensil becomes tamei again. This takanah is called tumah yeshanah, which I will translate as tumah revisited.


The first fully recyclable, non-metallic material discovered by mankind was glass. Broken glass can be melted down, shaped and cooled into new appliances in a process somewhat similar to metals. Since glass and metal share this quality, Chazal included glass in the category of items that can become tamei (Shabbos 16a). We will soon see that later authorities disputed whether other materials that can be recycled this way, such as some plastics, are miderabbanan also treated like metal items, or whether this ruling is unique to glass.

Tevillas Keilim

The Gemara (Avodah Zarah 75b) quotes Rav Ashi that, in addition to the requirement to toveil metal items that are intended for food use and that came from a non-Jew, we are also required to immerse glass dishes, for the same reason mentioned above — glass is recyclable by melting and reconstructing.

New metals

At this point, let us address our opening question: What is the halachic status, germane to the laws of tumah and taharah, of metals that have been discovered and isolated since the times of Chazal, which include zinc, chromium, manganese, nickel, magnesium, platinum, aluminum, titanium and many others?

There are differing approaches among later authorities regarding how halacha views these “new” metals, which results in different opinions regarding the laws of tumah and the laws of immersing utensils:

1. All metals have the same halachic status min haTorah as the six metals mentioned in Chumash (Yevakeish Daas of the Tiferes Yisrael, #44).

2. Any item that is recyclable is mekabeil tumah and requires tevillas keilim miderabbanan (Shu’t Ohel Avraham #24).

3. Only the six types of metal that the Torah mentions become tamei, and not any of the newly discovered ones. This position is suggested by Rav Moshe Feinstein (Shu’t Igros Moshe, Yoreh Deah 2:164) and by Rav Yaakov Kaminetzky (Sefer Tevillas Keilim,page 243). Shu’t Melamed Leho’il specifically concludes that, among recyclable materials, only glass is required to be treated like metal, because this is the only instance in which Chazal created this ruling. In other words, the fact that another material now exists that is also recyclable, like the six metals of the Torah and glassware, does not mean that this material is susceptible to tumah or requires tevillas keilim.

Because of the dispute between the Ohel Avraham,mentioned above, and the Melamed Leho’il, some authorities rule that utensils used for food and made from a recyclable material other than the six stated in the Torah and glass should be immersed, but without a brocha (Shu’t Minchas Yitzchak 3:76, 77, 78; 4:114:4).

Majority of alloy

As we noted above, the Mishnah proves that an alloy’s halacha follows a majority of its composition, so this dispute between the Ohel Avraham and the Melamed Leho’il will not affect the halachic status of bronze, pewter or steel. Steel is predominantly iron, and pewter is predominantly tin; therefore, items manufactured from these alloys are mekabeil tumah and require tevillas keilim min haTorah. It would affect the unusual variety of brass in which the copper component is less in volume than the zinc and other components. (Copper is slightly lighter than zinc, so a brass item made of 50-50 copper and zinc by weight, actually contains more copper than zinc by volume.)

Tumah of metals

According to many authorities, metals have a special status relative to the laws of tumah, which requires an introduction. In general, the highest level of tumah anything can ever become is called av hatumah, which should be translated as main category (or level) of tumah. There is one level of tumah, that of a meis, which makes other items into an av hatumah. For this reason, Rashi (Pesachim 14b and 17a; Bava Kama 2a) refers to a meis as avi avos hatumah, or super-category of tumah.


The Gemara (Pesachim 14b; Nazir 53b) teaches a principle call cherev harei hu ke’chalal,which means that, although usually only a meis can have the halachic category of being an avi avos hatumah, a vessel that touched a meis may also have this level of tumah. There are three major opinions among rishonim as to which types of utensils can have this law.

1. Those who rule that the principle of cherev harei hu ke’chalal applies only to metal utensils (Rashi, Shabbos 101b; Pesachim 14b and 97a; Rabbeinu Chananel, Pesachim 14b; Tosafos, Nazir 53b and 54b; Rabbeinu Tam, quoted by Tosafos, Bava Kama 2b). We should note that which metals are now included in this ruling will depend on the dispute among acharonim I quoted above as to whether newly discovered metals are mekabel tumah min haTorah, miderabbanan or not at all.

2. Those who rule that the principle of cherev harei hu ke’chalal applies to all utensils that can become tamei and subsequently made tahor through immersion in a mikveh or spring (Rambam, Hilchos Tumas Meis 5:3; Rabbi Yitzchak ben Malki Tzedek, cited in Rash, Ohalos 1:2; Bartenura and Eliyahu Rabbah, Ohalos 1:2).

3. Those who understand the Mishnah and Gemara of cherev harei hu ke’chalal in a different way, concluding that utensils can never become avi avos hatumah (Raavad, Hilchos Tumas Meis 5:3).

Pure gold

So far, we have been discussing, predominantly, copper, other less precious metals, and their alloys. At this point, I want to discuss the second of our opening questions, concerning gold alloys: A bell made of 100% gold will not ring because the metal is too soft. For a gold bell to ring, it must be an alloy including a small percentage of a different metal. So, how can the Torah say that the bells were manufactured from “pure gold.”

The questioner here, a frum and Torah-knowledgeable metallurgist, assumed that a statement that something is made of zahav tahor, “pure gold,” means that there is no alloy of other metals. He understood that the gold used for the bells must have been an alloy containing a small percentage of another metal, which would have the desired properties of both strength and resonance. This would allow the bells to produce a ringing sound when the kohein gadol walked, fulfilling their purpose as bells.

Let me explain his question a bit more:

Most gold vessels and garments of the Mishkan required that they be made of zahav tahor (see Shemos 25:11, 17, 24, 29, 31, 38; 28:14, 22, 36; 30:3). However, the two rings of the choshen are described only as zahav, omitting the word tahor (Shemos 28:23); similarly, the gold thread is not described as tahor (28:15), nor are the two rings manufactured along the sides of the mizbeiach hazahav (30:4), nor the gold overlay of the poles that carry the mizbeiach (30:5). These references might indicate that when the Torah requires “gold,” but does not specify “zahav tahor,” that it is not 100% gold, but a gold alloy that is more suitable for use as a thread, or carrying ring or pole.

Golden bells

When Betzalel and his assistants manufactured the bells attached to the hem of the kohein gadol’s garment, the Torah says that he made them from “pure gold” (Shemos 39:25). However, in parshas Tetzaveh (Shemos 28, 33), where we are commanded about the manufacture of these bells, the Torah states simply that they are made of gold, omitting the word tahor. Thus, we have a conundrum: the Torah does not require that the bells be manufactured of zahav tahor, yet Betzalel made them that way. Regarding all the other items manufactured for the Mishkan, when the mitzvah stated to make them from zahav and not necessarily zahav tahor, no mention is made that Betzalel and his assistants manufactured them from zahav tahor!

The answer is that the term “pure/tahor” gold may mean that it is 100% gold, or it might mean that the gold is tahor, meaning that it is not tamei. Bells made for jewelry or as a tassel hanging from the hem of a garment are not considered utensils, and therefore cannot become tamei. Thus, there would be no need to manufacture them from tahor gold. Only when they are manufactured to ring and, therefore, they contain a clapper, are they susceptible to tumah, in which case it is important to note that they are tahor and not tamei. When we are commanded to make them, the Torah emphasized that these bells can ring – which means that they are potentially susceptible to tumah. It is thus understood that they must have been made tahor. At the time of their manufacture, we need to be reminded that they must be made tahor, since they are susceptible to tumah (Meshech Chachmah, Shemos 39:25). Thus, the reference to their being “pure” does not mean that they were 100% gold. They needed to be an alloy that has some added other metal so that they will ring.


Among the various mitzvos dealt with in this article is the mitzvah requiring that we immerse our food utensils prior to use. This tevillah elevates their sanctity, so that they can now be used for a Jew’s table. Thus, not only food that a Jew eats requires special care, but also the equipment with which he prepares that food.