This article is an attempt to provide a review of some of the pertinent details of the mitzvah of shatnes, to educate consumers so that they avoid purchasing garments containing shatnes, and to dispel many of the myths about certain types of clothing and textiles that do or do not contain shatnes. We hope to reduce the all too frequent instances in which the joy one naturally experiences upon purchasing a new garment is diminished when shatnes is discovered.

Defining Shatnes
There are two pesukim in the Torah that refer to shatnes. In Vayikra 19:19, we have, “Ubeged kilayim shatnes lo ya’aleh alecha.” A garment composed of a mixture which is shatnes should not be draped upon oneself. In Devarim 22:11 we find a different expression of this same mitzvah, “Lo silbash shatnes tzemer uphishtim yachdav.” Do not wear shatnes, wool and linen together. Chazal tell us that these two pesukim complement one another. In Devarim the Torah forbids actual wearing of shatnes – levisha, whereas the Vayikra prohibition of shatnes includes he’elah – draping shatnes over one’s body. The Gemara in Yevamos 4:2 explains that draping is prohibited only if it is done in a way which is similar to wearing, i.e. where some benefit is derived from the shatnes such as being covered or warmed. However, the act of a peddler carrying shatnes over his shoulder or a tailor allowing shatnes to lie on his lap while sewing would not be prohibited.

The word shatnes is an abbreviation of three words: shua, tuvi and nuz which describe three different stages in the processing of the wool and linen fibers. Although there are differences as to exactly which processes are being referred to, most opinions maintain that shua, refers to the combing of the raw fiber. Tuvi, is the process of spinning fibers into a thread, and nuz, refers to the twisting or weaving of the threads into cloth. The Gemara Niddah 61:2 states two opinions whether a material, in order to constitute shatnes forbidden by the Torah, requires all three of the above mentioned processes, or if only one of these processes sufficiently qualifies for a shatnes fabric. Since the Torah expresses and combines these three in the one word shatnes, we follow the opinion that a wool and linen mixture is shatnes, forbidden by the Torah, only if all three processes have been performed in the making of the material.

There is a well known disagreement between Rashi and Rabbeinu Tam with respect to these three processes. Rashi‘s opinion is that both the wool and linen be combined in their raw states, the two fibers are combed, spun and woven together and form a material that qualifies as shatnes forbidden by the Torah. Rabbeinu Tam disagrees and states that the requirement of shua, tuvi, and nuz is fulfilled even if the wool and linen are separately combed, spun and twisted and are later combined by weaving or attaching the two together. Thus, according to Rabbeinu Tam, the criteria for shatnes forbidden by the Torah will have been met even if they are attached by as little as two stitches as long as both the wool and linen have each undergone the process of shua, tuvi, and nuz.

Other Fabrics
When we speak of wool, we are only referring to wool obtained from sheep or lambs. Other materials, such as camel’s wool, mohair, angora, cashmere, alpaca wool or vicuna, present no shatnes problems. Similarly, linen refers only to fibers derived from the flax plant, whereas other bast fibers, such as ramie, hemp or jute, may be combined with wool. With respect to ramie, one should be aware that it is difficult to distinguish this material from linen even with the use of a microscope. Since clothing manufacturers, particularly those from abroad, are guilty of mislabeling the fabric contents, clothing containing wool and ramie should not be worn unless an expert in the field of shatnes has verified that the fabric contains no linen.

Separate Garments
From the verse in Devarim we learn that the wool and linen must be joined together in some permanent fashion. Thus, there is not a shatnes violation if one wears a linen jacket and wool pants or has a linen scarf wrapped around a woolen dress. It is also not forbidden to attach the linen and wool with snaps, buttons or zippers, since these are not considered a permanent binding. However, one should be aware that one may not wear a linen shirt or blouse beneath a wool jacket, since the shirt or blouse cannot be removed without taking off the jacket. This restriction would not apply in the case of a wool tie under a linen jacket, since the tie can be easily removed without taking off the jacket.

Bitul – Nullification
A question that is often asked is “Are small amounts of linen botul, nullified, in a wool garment?” The answer depends whether the linen at the time of question is in the fibrous stage or was it already formed into threads. Fibers, which are the thin delicate strands that can be easily observed when a thread is untwisted, can become botul to other types of fibers as long as it is still in the fibrous stage combined with materials other than wool. Threads of completed linen cannot become botul to other threads. The ramifications of this are important in considering whether an item is or is not shatnes. For example, in threads with a 25% linen and 75% cotton composition, the linen becomes botul to the cotton and these threads are treated for halachic purposes as though they were 100% cotton threads and may be woven together with woolen threads to form a non-shatnes fabric. If, however, a single linen thread is woven together with wool, although the total content of linen is only a fraction of 1%, the fabric would be considered shatnes since the single linen thread creates shatnes problems.

A similar example, actually quite common, is the situation where the wool is botul, such as in a linen jacket containing interfacing made up of polyester, animal hairs and wool. As long as every individual thread in the interfacing contains less wool than polyester, the threads are halachically treated as though they contain no wool at all. Obviously, only well trained shatnes checkers who are experienced in the use of a microscope and in making fiber counts should attempt to make this determination.

Reprocessed Materials
The question of fibers vs. threads is also of considerable importance when determining the shatnes status of clothes containing reprocessed materials or unknown fibers which are frequently listed on garment tags as O. F. (other fibers). Most often the source of these fibers is shredded rags made up of a large variety of materials. Although, for the most part, the shredding process breaks the threads down into their component fibers, which would, therefore, allow small amounts of linen to become botul, small fragments of threads do remain intact, and thus the laws of bitul do not apply. In practice, it has been the experience of the Vaad Hakashrus’ Shatnes Laboratory that a very significant percentage of such clothing are indeed shatnes. For this reason, we recommend that, when possible, one avoid purchasing garments with reprocessed materials or unknown fibers.

There is another practical reason to avoid buying garments which have other fibers, or for that matter, reprocessed wool. The very reason why one purchases a wool garment in the first place is because of certain characteristics such as retention of shape, superior appearance and texture, and ability to repel moisture. These desirable characteristics of wool are, for the most part, due to the long undamaged fibers found in virgin wool. On the other hand, fabrics containing unknown fibers or reprocessed wool, because they are made from chopped up recycled clothes, contain short damaged fibers and are of much inferior quality. Although, to the untrained eye, a new garment may appear similar to one made from virgin wool, most likely, it will soon lose its shape and begin to pill, making such a purchase unwise despite the initial lower cost of such a garment. This also explains why garments made from reprocessed materials often have irregular textures and off-colored spots caused by inconsistencies in the recycled materials.

Reasons Behind the Mitzvah
Although the mitzvah of shatnes is a chok, one for which the Torah offers no explanation or rationale, we nevertheless find in the commentaries several clues as to why the Torah specifically precludes a wool and linen mixture. The Rambam, in his Moreh Nevuchim, states that in ancient times sorcerers, in performing their witchcraft and in communicating with “demons”, frequently used garments composed of both wool and linen. To prevent us from being associated in any way with these evil practices, our Torah forbids us from wearing clothing containing this mixture.

Other commentators suggest that the prohibition of wearing shatnes is related to the special clothes containing both wool and linen worn by a kohein while performing the avodah in the Bais Hamikdash, Holy Temple. To wear this mixture at other times or places would be profaning that which should be reserved exclusively for use in the Bais Hamikdash.

Rabbeinu Bachya writes that the prohibition of shatnes is related to Kayin and Hevel, Cain and Abel, the first naturally born human beings who each represented opposite extremes of good and evil. Wool, which represents the sacrifice brought by the shepherd Hevel from sheep, and linen or flax seeds, which the Medrash tells us was the species offered by Kayin, cannot be mingled, as it ultimately led to the destruction of both Kayin and Hevel. Thus according to Rabbeinu Bachya, the Torah precludes the use of shatnes because the combination of wool and linen is symbolic of the joining together of two opposing forces which allow certain celestial powers to exert destructive forces on the world. If, however, we make a conscious effort to keep wool and linen totally separate and distinct, we counteract these forces and actually help generate greater peace in the world.

Training to Become a Shatnes Checker
There is a great need, particularly in smaller communities, to have greater availability of qualified shatnes checkers. For those communities or individuals serious about undergoing a training program, we recommend that you contact Rabbi Joel Shochett, head of The National Committee of Shatnes Testers and Researchers in Lakewood, NJ, at 732-905-2628.