What Is Shatnez? Ancient Practice of Checking Garments for Linen and Wool Continues

A navy suit jacket with its beige collar lining taken out
A wool suit’s collar lining being removed and checked for linen | Photo by Yosef Sayagh

Under a microscope, linen looks like a bamboo stalk, with long, straight fibers running up and down a thread. Wool, on the other hand, looks like snakeskin, with scales that jut up and over each other.

Rabbi Yosef Sayagh is adept at detecting the differences between these fibers and more. As director of International Headquarters of Professional Shatnez Laboratories, the Lakewood, New Jersey-based rabbi is one of the foremost shatnez testers in the country.

Shatnez, or the mixing of wool and linen in garments, is prohibited under Jewish law. The practice of testing garments for shatnez is an ancient one, but it is still being carried out in the Greater Philadelphia area.

After a Jewish person — usually Orthodox — buys a garment, they take it to a shatnez tester. The trained rabbi will check the item, usually a wool jacket, for any signs of linen, most commonly hidden in the jacket’s lining or reinforcements around the collar. If the rabbi finds linen, they will remove the component from the jacket and have it replaced. Other fiber objects, such as rugs, also need to be tested.

The process takes about five minutes in most cases, but in others, such as with garments with synthetic fabrics or wool blends, testing can take longer and require use of microscopes to detect certain fibers.

“The question is, how much linen is going to render a garment shatnez? And the answer is, a minute thread, a small thread of linen in an entire garment of wool,” Sayagh said. “That’s enough to make it shatnez. So therefore, the removal of the collar has to be done by an expert.”

Buyers can’t just trust the tag to display information about the makeup of a garment, said Lower Merion-based Rabbi Yisroel Akerman. American regulations only require that labels include fibers that make up 2% or more of a garment. A single thread of linen in a wool garment would not be noted in a label.

“There’s well over 100 components here,” Akerman said. “There’s reinforcements, there’s canvases, there’s shoulderpads, there’s tape — tape is a whole other place for reinforcements. I’m not even going to get into pockets, themselves. … So none of these materials are listed on the tag.”

Akerman has been checking shatnez for clients from Orthodox synagogues on the Main Line for about five years. Jewish-owned stores such as The Men and Boys Store in Warminster have a rabbi come in and batch test the garments for shatnez and, upon purchase, test them again.

“It’s a mitzvah. It’s important. It’s something I’ve been doing, so I’m not going to stop,” said Bonnie Greisler, owner of The Men and Boys Store.

Greisler has been providing shatnez testing services since 1981, when she worked at Fleet’s men’s store at Castor and Magee avenues. In the 42 years she’s been providing testing, there’s always been a demand, she said. Shatnez testing is particularly popular around the holidays and beginning of the school year, when people are buying new clothes. 

The origins of the prohibition of shatnez in Jewish tradition is considered chok, an unexplainable law. The prohibition of mixing wool and linen is called kilayim.

“The word shatnez is not actually a real word,” Akerman said.

Shatnez comes from the combination of three Hebrew words that refer to the different steps of garment production: combing, spinning and weaving.

Akerman said that though with unclear origins, there’s a few reasons why shatnez prohibition has persisted in Judaism. In some explanations, according to Chabad Rabbi Lorne Rozovsky, pagan priests mixed wool and linen in their garments, and prohibiting shatnez was a way for Jews to separate themselves from pagan traditions.

Another explanation is that Adam and Eve’s sons Cain and Abel brought these respective fibers as offerings, with Cain the farmer bringing flax, or linen, and Abel the shepherd bringing wool. Some even say that the combination of the two fibers was lethal to Abel. 

Though Jewish texts have commentary about clothing worn by the Torah’s first humans, the tradition still has to contend with changing technology and materials, including synthetic fabrics.

In the last 10 years, Greisler has noticed a difference in the garments coming into her store. Instead of wool, manufacturers use synthetic fabrics such as polyester. 

“Manufacturing and fabrications, they’re not really using that fabric (wool) anymore,” Greisler said. “So it’s become quite easy and less complicated to have the clothing tested.”

Rabbis believe that shatnez testing is still part of a due diligence done to ensure garments are halachically sound, especially with more lenient clothing labeling in the U.S. The spiritual leaders are looking for the next generation of Jews able to provide this service to Orthodox community members.

“Is there enough people trained?” Sayagh said. “No, there isn’t enough people trained.”

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